UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

A self-framing PCM system Shimokura, Satoru Howard 1963

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-UBC_1963_A7 S4 S3.pdf [ 3.8MB ]
Metadata
JSON: 831-1.0105036.json
JSON-LD: 831-1.0105036-ld.json
RDF/XML (Pretty): 831-1.0105036-rdf.xml
RDF/JSON: 831-1.0105036-rdf.json
Turtle: 831-1.0105036-turtle.txt
N-Triples: 831-1.0105036-rdf-ntriples.txt
Original Record: 831-1.0105036-source.json
Full Text
831-1.0105036-fulltext.txt
Citation
831-1.0105036.ris

Full Text

A SELF-FRAMING  PCM  SYSTEM  by  SATORU HOWARD SHIMOKURA B.A.Sc., U n i v e r s i t y  of B r i t i s h  Columbia,  A THESIS SUBMITTED IN PARTIAL FULFILMENT THE REQUIREMENTS FOR  1961  OF  THE DEGREE OF  MASTER OF APPLIED SCIENCE i n t h e Department of Electrical We  accept  required  this  thesis  Engineering as c o n f o r m i n g  t o the  standard  THE UNIVERSITY OF B R I T I S H COLUMBIA February,  1963  In presenting this thesis in partial fulfilment of. the requirements for an advanced degree at the University of British Columbia, I agree that the Library shall make i t freely available for reference and study.  I further agree that permission  for extensive copying of this thesis for scholarly purposes may  be  granted by the Head of my Department or by his representatives. It is understood that copying or publication of this thesis for financial gain shall not be allox^ed without my written permission.  H.  Department of  E l e c t r i c a l Engineering  The University of British Columbia, Vancouver 8, Canada. Date  Shimokura  February 22,  1963  ii  ABSTRACT  A single communication seven d i g i t s  channel  pulse  code m o d u l a t i o n  (PCM)  system i s d e s c r i b e d u s i n g a b i n a r y p e r code group and a s a m p l i n g  speech  code  with  r a t e o f 8000 p e r  second. A unique  f e a t u r e o f the system i s the p u l s e  s y n c h r o n i z a t i o n or framing the  operations  scheme t h a t i s employed  of the coder  and t h e d e c o d e r .  t h e use o f a u x i l i a r y  information i s inherent The and  coder  i s a modified  Hafer.  i n the coded  operates  i s basically  The  r e c e i v e d code p u l s e s  are  s t o r e d as v o l t a g e s  to  after  for  achieved  principle  p r e v i o u s l y d e s c r i b e d by  on a c a p a c i t o r .  count  The v o l t a g e  sample t a k e n  type.  on t h e  i n times  a t the  i n d i c a t e t h a t the performance  reproduction  of speech.  proposed framing  The g r o u p  i s adequate synchronwas  n o i s e was i n a u d i b l e .  scheme i s a d a p t a b l e  i n t h e use o f t h e d i g i t s  coder.  and c o r r e c t f r a m i n g  so s h o r t t h a t m i s f r a m i n g  s p e e c h s y s t e m s where s i m p l i c i t y economy  framing  signals.  one o f t h e p u l s e  scheme p e r f o r m e d p e r f e c t l y  The  The  p r o d u c e b i n a r y amounts o f c h a r g e w h i c h  o f the o r i g i n a l  results  good q u a l i t y  ization  digits.  framing  one c y c l e o f d e c o d e r o p e r a t i o n i s p r o p o r t i o n a l  the amplitude Test  co-ordinate  correct  on t h e c i r c u l a t i n g p u l s e  v e r s i o n of a coder  The d e c o d e r  capacitor  framing  to  A method i s  o u t l i n e d w h e r e i n t h e system i s a b l e t o e s t a b l i s h without  group  to small  i n t h e i n s t r u m e n t a t i o n and are  important.  PCM  viii  ACKNOWLEDGEMENT Acknowledgement i s g i v e n t o the N a t i o n a l R e s e a r c h for  sponsoring t h i s project  u n d e r B l o c k Term G r a n t BT-68 a n d f o r  the Research A s s i s t a n t s h i p granted to the Acknowledgement  is  Council  gratefully  author.  g i v e n t o P r o f e s s o r P . K.*  B o w e r s , the s u p e r v i s o r of the p r o j e c t ,  f o r h i s guidance  and  encouragement  Thanks a r e a l s o  given  throughout the p r o j e c t .  o t h e r members o f t h e helpful  suggestions.  staff  and t o t h e g r a d u a t e  students  for  to their  iii  TABLE OP  CONTENTS Page  Abstract  i i  List  of I l l u s t r a t i o n s  List  of Tables  v v i i  Acknowledgement  ............. •••»..  1.  Introduction  2.  Some T h e o r e t i c a l C o n s i d e r a t i o n s  3.  4.  5.  viii 1  2*1  The  Sampling P r i n c i p l e  2*2  Bandwidth Requirements  2.3  S i g n a l Power R e q u i r e m e n t s  2.4  Noise  2.5  Information  i n a PCM  .................  ..«•......  7 7  ..................  System  8 8  Capacity  A P r o p o s a l f o r Group S p e e c h System  7  9  Synchronization f o r a  PCM H  3.1  R e q u i r e m e n t s of a S y n c h r o n i z a t i o n Scheme  3.2  A Proposal  3.3  E v a l u a t i o n of the P r o p o s a l  13  3.4  Misframing  21  f o r Group  Synchronization  ...  11  .......  12  D e t e c t i o n and C o r r e c t i o n .,  System D e s i g n  27  4.1  The D e c o d e r  27  4.1.1  The B a s i c D e c o d e r C i r c u i t  27  4.1.2  Operation  31  o f the Decoder  4.2  Operation  of the Framing C i r c u i t  4.3  Operation  o f t h e Coder  ...........  34 36  System T e s t s  39  5.1  39  System P e r f o r m a n c e  iv Page  6.  5.2  L i n e a r i t y Tests  41  5.3  Noise  41  5*4  Waveforms  and D i s t o r t i o n  44  Conclusions  46  Appendix  1 - D e r i v a t i o n o f F i g u r e 3.1  48  Appendix  2 - Circuit  Details  of the Decoder  Appendix 3 - C i r c u i t  Details  o f t h e Coder  References  ....  51  ......  64 71  L I S T OF  ILLUSTRATIONS  Figure  Page  1.1  A T y p i c a l PCM  3.1  Amplitude V e r s u s Frequency C h a r a c t e r i s t i c of I n p u t S i g n a l s f o r O p e r a t i o n o f PCM F r a m i n g Circuit ..••«.«••«  14  Maximum Sound P r e s s s u r e s i n V a r i o u s F r e q u e n c y Bands f o r l / 8 Second I n t e r v a l s o f C o n v e r s a t i o n a l Speech . . . . . . . . . . . . . . . . • • • o . . . . . . . . . .  14  E f f e c t of Pre-Emphasis i n the Amplitude V e r s u s Frequency C h a r a c t e r i s t i c o f Speech .............  15  3.2  3.3  3.4  Power S p e c t r u m PCM  System  .  of Q u a n t i z a t i o n Noise i n V a r i o u s  Systems  18  3.5  M i s f r a m i n g by  3.6  I n p u t S i g n a l t h a t C r o s s e s t h e 64 L e v e l W i t h S l o p e o f L e s s t h a n 32 L e v e l s / S a m p l i n g P e r i o d D e c i m a l Numbers 70 and 40 I n c o r r e c t l y Decoded as 12 and 80 o r 81  3.7  3.8  1 Digit  •»••••••  21  Time R e q u i r e d f o r M i s f r a m i n g E r r o r  22 23  Indication  and S h i f t i n g  25  4.1  Basic  4.2  B l o c k Diagram  of Decoder  ..••••........*  32  4.3  B l o c k Diagram  of Framing  Circuits  35  4.4  B l o c k Diagram  o f Coder  5.1  Input S i g n a l Frequency — Amplitude C h a r a c t e r i s t i c f o r S u c c e s s f u l O p e r a t i o n o f t h e F r a m i n g Scheme .  40  5.2  Linearity  Test  o f t h e Coder  42  5.3  Linearity  Test  of the Decoder  5.4  N o i s e and D i s t o r t i o n Measurement  5.5  Waveforms  A—1.1  Circuit  2  of the Decoder  Assumed Form o f I n p u t S i g n a l s  ...................  28  36  .................. ...............  43 44 45  •••............•».  48  vi Figure A-2.1  A-2.2  Page Input A m p l i f i e r , Generators  Delay Monostable  and P u l s e 53  Driven Oscillator,  Amplifier  and Square Wave  Generator  54  A-2.3  Count-Down-By-Seven C o u n t e r  55  A-2.4  Current Generator  A-2.5  Charge T r a n s f e r Gate  57  A-2.6  Discharge  57  A-2.7 A-2.8  L e w i s G a t e , V o l t a g e C o m p a r a t o r , and D i o d e Gate ( a ) S c h m i t t t r i g g e r ( b ) PG1 ( c ) D e l a y Monos t a b l e f o r PG2 (d) PG2  58  A-2.9  Pulse Generators:  ..  60  A-2.10  Counter  Waveforms and I n t e r v a l s D e f i n e d  .....  61  A-2.11  Waveforms on C, , C C-, Due to R e c e i v e d o f 43 and 91 7.  Values  A-2.12 A-3.1  CGI a n d S t o r a g e  C a p a c i t o r C^  Gate  ( a ) PG3 ( b )  PG4  ot  F r a m i n g C i r c u i t Waveforms Due t o Decoded V a l u e s o f 20 and 91 (a) Master GP1  (d)  C l o c k (b)  Frequency  Delay Monostable  (e)  56  59  62 63  Divider (c)  GPld  66  ( c ) GP3 .  67  A-3.2  Pulse Generators:  A—3.3  I n p u t A m p l i f i e r , Diode Gate 1, S c h m i t t T r i g g e r s , S u b t r a c t o r and V o l t a g e D o u b l e r Amplifier Double E m i i t e r F o l l o w e r G a t e , Charge T r a n s f e r C i r c u i t s , D o u b l e E m i t t e r F o l l o w e r , D i o d e Gate 2  69  C o d e r T i m i n g Waveforms  70  A-3.4 A—3.5  ( a ) GP2 (b) GP2d  .........  68  vii L I S T OF  TABLES  Table 3*1  A-l.l A-2.1  Page C o n d i t i o n s and A p p r o x i m a t e P r o b a b l e M i s f r a m i n g E r r o r I n d i c a t i o n ••••  Times f o r  T a b l e o f F r e q u e n c i e s of I n p u t S i g n a l and Corresponding P e r m i s s i b l e S i g n a l Amplitudes Data  f o r Current Generators  24 ...  50  ..*«*............*.  52  0  1 A SELF-FRAMING PCM  1.  C o m m u n i c a t i o n by  SYSTEM  INTRODUCTION  pulse  code m o d u l a t i o n  (PCM)  methods i s (1 2  w e l l known and PCM  u s e s b i n a r y p u l s e s , and  o n l y the and  presence  exact  timing  r e d u c e s the t a l k , the o f the be  i s described  o f the  pulses.  regenerated  at each r e p e a t e r *  designed  cumulative,  b e t t e r t h a n the  long-haul for this  requirements  feature  A typical  by  the  values is  after  sampler. t o one  i s the o f the  PCM  must be o f the  entire  increased terminal  quantizer  a binary  to  penalty  cross-  design can  that  repeater  a to  distortion  requirements  system.  It is  this  so d e s i r a b l e t h a t must  channel bandwidth  be  and  equipment.  system i s i l l u s t r a t e d  i n Figure  i s sampled a t f r e q u e n t r e d u c e s the  o f many d i s c r e t e v a l u e s  t h e n coded i n t o  The  greatly  and  the  and  and  sampled  1.  to  its  The  intervals  amplitude  each quantized  code, a c c o r d i n g  .  shape  signals  t h a t makes PCM  systems.  filtering,  The  coded  designed  the  pulses  simplifies  l i n k f r o m one  repeatering  communication  complexity  signal,  and  systems, since noise  each r e p e a t e r  concept of r e g e n e r a t i v e  input  of b i n a r y  ' '  sense  ignores  i t i s only necessary  to h a n d l e t h e  are  increased  and  Furthermore, since binary  n e x t , whereas i n a n a l o g  paid  use  power r e q u i r e m e n t s ,  the  for  system needs to  pulses  The  literature  system's s e n s i t i v i t y t o n o i s e , d i s t o r t i o n  signal  be  h e n c e , the  o r absence of the  repeaters.  repeater  e x t e n s i v e l y i n the  3)  sample  amplitude.  Low PASS PUTER  Ti ^ I N G CIRCUIT  A )  t  QUANTISER  Low/ PASS  DECODER  >•  D E MODULATOR Figure  The  decoder  reverses  1.1 A T y p i c a l PCM  the o p e r a t i o n  is  to r e c o n s t r u c t the amplitude  by  the quantizer.  obtained  by It  that not  of the coder.  sample p r e s e n t e d  The r e c o n s t r u c t e d  Its function t o the coder  s p e e c h waveform  i s then  filtering. i s apparent  that  t h e sample a m p l i t u d e e x a c t l y the amplitude  of sampling. be  System  This  a small  that  error results  i s actually  from the f a c t  coded by t h e c o d e r i s  o f t h e s p e e c h waveform a t t h e i n s t a n t  i s the s o — c a l l e d q u a n t i z a t i o n e r r o r .  r e d u c e d b y i n c r e a s i n g t h e number o f d i s c r e t e v a l u e s  I t can or l e v e l s  used by the system. Many methods have b e e n d e v e l o p e d t o code a n a l o g i n t o PCM s i g n a l s and, t h e r e v e r s e s i g n a l s back i n t o forward  analog  method o f c o d i n g  signals.  operation,  t o decode t h e c o d e d  P e r h a p s t h e most  i s the pulse  signals  straight-  c o u n t method as d e s c r i b e d  by  Black  and E d s o n  (4)  (5) and by A r m s t r o n g ^ .  medium speed b u t i s i n h e r e n t l y awkward operations  necessary  code i s i n p a r a l l e l to  be c o m p a t i b l e  t h a t the  form and must be c o n v e r t e d standard  i s of  b e c a u s e o f t h e number  and b e c a u s e o f t h e f a c t  with  method o f c o d i n g  T h i s method  into  output  serial  t r a n s m i s s i o n methods.  makes use o f e l e c t r o n beam c o d i n g  of  A  form  second  tubes.  PCM  (6) systems embodying c o d i n g (7) Meacham and P e t e r s o n the  tube r e q u i r e s  these  t u b e s a r e d e s c r i b e d by S e a r s  .  T h i s method o f c o d i n g  considerable  power, s p a c e  drawbacks make i t u n s u i t a b l e w i t h  principle  i s very  f a s t but  and m a i n t e n a n c e and  t r a n s i s t o r i z e d equipment. (8)  A t h i r d method i n v o l v e s t h e use o f f e e d b a c k . the  and by  o f t h e use o f f e e d b a c k i n PCM  Smith  describes  c o d e r s and an (2)  experimental A novel  system u s i n g  approach to coding  .  .  a coder u s i n g  probably  t h e most d i f f i c u l t  exception  i s described  unsuccessful  I n PCM,  of i t s apparent  coder  tubes,  t o c o n s t r u c t a decoder u s i n g  i s d e s c r i b e d by as i n o t h e r  using  simplicity, i s  method t o i n s t r u m e n t .  W i t h the analogous An  the c i r c u l a t i n g  Chang^ ^. 1 1  pulse  c o o r d i n a t i n g the o p e r a t i o n s This  A similar  the methods d e s c r i b e d have b e e n c o n s t r u c t e d .  attempt  principle  of c i r c u l a t i n g  T h i s method i s a l s o o f  o f t h e method u s i n g bea.m c o d i n g  decoders using  provided.  tubes.  i s d e s c r i b e d by H a f e r ^ ^ .  medium s p e e d b u t , i n s p i t e  of  f e e d b a c k methods  He makes use o f t h e p r i n c i p l e  and d e s c r i b e s  transistors  pulse  using  Goodall  (9)  by F e d i d a pulses  f e e d b a c k i s d e s c r i b e d by  m o d u l a t i o n schemes, some means  o f the c o d e r and d e c o d e r must be  i s the f u n c t i o n of the s y n c h r o n i z a t i o n  scheme.  The  timing  circuit  a t the  coder  transmits  i n f o r m a t i o n which i s then detected  by  the  the  synchronizing  retiming  circuit  at  the  decoder. The First, pulse  synchronization  i t must make known t o the r e p e t i t i o n frequency.  S e c o n d , i t must i m p a r t timing.  This  select,  out  must be in  train  originally  "framing",  scheme e n a b l e s  of u n i f o r m l y and  not  things.  timing  the or  basic  problem.  pulse  group  group  the  decoder  to  spaced p u l s e s  and  spaces,  spaces t h a t r e p r e s e n t  the  sample  coded a t the  at frequent  transmission w i l l  regarding  two  phase o f the  i s the p u l s e  is called  groups of p u l s e s  sent  This  framing  of a l o n g  correct  amplitudes  The  d e c o d e r the  information  operation  synchronization.  the  scheme must a c c o m p l i s h  coder.  The  intervals  so t h a t any  adversely  affect  framing  information  temporary  break  the  operation  of  the  accomplished  s i n c e the  required  system. Pulse information  retiming  is easily  i s inherent  i n the  needs o n l y to d e t e c t  the  l e a d i n g edges o f the  pulses  oscillator  or r i n g i n g  P e r h a p s the  the  framing  time of a r r i v a l are  circuit  into  t o use  information.  But  channels.  A b e t t e r method w o u l d be  frequent  system u t i l i z e s to  i n a code g r o u p o r even an  intervals  to  c a r r y the  decoder  pulses. a  The  local  of e s t a b l i s h i n g p u l s e transmission  t h i s method  i f the  The  phase.  a separate  especially  more d i g i t s  overall  o f the  then used to p u l l  most o b v i o u s way  s y n c h r o n i z a t i o n would be for  transmitted pulses.  framing  only  i s very a few  sacrifice entire  the  group  channel  wasteful, message use  o f one  code g r o u p a t  information.  The  use  of  or  5 parity  checks f a l l s  more e c o m o n i c a l systems w i t h  into this  t h a n the  three  category.  first,  is still  i n v o l v e s the  use  i n w h i c h the  synchronizing  continuous  The  h e n c e , a minimum of i n f o r m a t i o n  third  small  and  most  synchronization  of s e l f - s y n c h r o n i z i n g codes. information  although  unsatisfactory for  message c h a n n e l s o r l e s s .  e c o n o m i c a l means o f a c h i e v i n g  and  T h i s method,  i s an  These are inherent  is sacrificed  by  codes  feature, the  trans-  (12) mission  channel. Ideally,  synchronizing  Stiffler i t would be  the  o f t r a n s m i t t i n g the designed little  system.  problem  i n the  this  is  codes.  the o f the  inform-  impossible.  most e f f i c i e n t I f the  means  system i s  rate, with  very  s e r i o u s problem.  of  However*  case of speech s i g n a l s * which are h i g h l y redundant i n sense,  p r o b l e m and  may  achieved  be  self—synchronization i s a less by  This t h e s i s presents problems encountered The  first  i n the  is basically the  one  relatively  a simple  simple  s o l u t i o n to  transmission  phase o f the  c o n s t r u c t i o n of a 7 d i g i t  p r o j e c t was  the  decoder, employing  o f the  pulse  the  basis.  coder b u i l t  amplitude-frequency  The by  final Hafer^  phase was 1 0  ^  some o f  The  storage.  or f r a m i n g  compatible  by  s e c o n d phase scheme  of s p e e c h  m o d i f i c a t i o n o f the  so t h a t i t was  the  and  capacitor  characteristic the  methods.  design  count type.  the  serious  of speech s i g n a l s  development of a group s y n c h r o n i z a t i o n  utilizing its  any  information  codes becomes a v e r y  theory  was  such  information.  at a high  information  It  sacrificing  i s t o d e t e r m i n e the  data  of  r e d u n d a n c y i n the m e s s a g e s * s y n c h r o n i z a t i o n by means  self—synchronizing  PCM.  use  Obviously,  synchronizing  to transmit  the  d e s i r a b l e to t r a n s m i t  information without  a t i o n c a p a c i t y o f the Therefore,  cites  with  PCM the  as  6 decoder. c o d e r * the developed  The  e n t i r e PCM  d e c o d e r , and i n this  systeitij the  incorporating  the  group s y n c h r o n i z a t i o n  t h e s i s , was  then  tested.  modified scheme  7 2.  This  SOME THEORETICAL CONSIDERATIONS  chapter  a s p e c t s o f PCM  and  o u t l i n e s a few  provides  of the  basic theoretical  background m a t e r i a l  for  subsequent  chapters.  2.1  The  Sampling P r i n c i p l e  (13) Nyquist  ' has  demonstrated that  b a n d w i d t h WQ  i s sampled a t a r a t e  will  a l l the  is PCM 2.2  contain  illustrated i s one  information  2WQ  such  Bandwidth  or g r e a t e r ,  i n that  i n a l l systems t h a t  i f a signal the  signal.  of samples  This p r i n c i p l e  employ s a m p l i n g  methods.  system. Requirements  (13) Nyquist  7  independent pulses  has  also  per  have a b a n d w i d t h o f a t the  the  transmission  l e a s t W/2.  This  interference.  interference  of previous pulses  pulses).  at the  provided  that  s y s t e m and override  the  o f one  intersymbol the  noise,  (intersymbol pulse  due  interference  establishes  interference transient  i s possible of  V  c h a n n e l must  of pulses  t o the  over a channel  to t r a n s m i t  condition  transmission  However*it  same r a t e  that  i n order  s e c o n d , the  minimum b a n d w i d t h f o r the  intersymbol as  shown t h a t  to  with is  no  defined  energy  transmit  l e s s e r bandwidth  can  be  t o l e r a t e d by  the  s i g n a l power i s i n c r e a s e d  sufficiently  to  f o r i t i s apparent that  as  the  bandwidth  8 is  reduced, there  ference  and  i s g r e a t e r and  difficulty  over  intersymbol a channel  frequency  V  design  of pulse  i n t e r f e r e n c e and  o f b a n d w i d t h W/2  Hence, a PCM  intersymbol  i n r e c o g n i z i n g the  However, i n t h e avoid  greater  digits.  systems i t i s u s u a l  transmit W pulses  cps  or  using n d i g i t s ° n(2V )  to  code one  = ^Q.  sample, w o u l d r e q u i r e  ^—  required  the bandwidth f o r d i r e c t  I n o t h e r w o r d s , the  n  a  bandwidth  transmission.  S i g n a l Power R e q u i r e m e n t s  The  signal  be  s u c h t h a t the  in  the  presence  power f o r a d e q u a t e PCM  d e c o d e r can of channel  higher  than  reasonable level  twice  the  p e r i o d and  at one-half  the  to  height to  distinguish  noise with  Hence, i t i s o n l y n e c e s s a r y  of the  set the  pulse  very  signal-to-noise ratio  low—a  to—noise ratio  i s required.  quality  transmitted  e n t i r e l y by  Noise  noise  system  pulses  from  height  decoder pulse  Given signal  spaces  slightly  expected  over  then  T h i s t h r e s h o l d power i s  o f 20 db  i s more t h a n  signal  i s then encoding  power,  limited  adequate-  signalthe  almost  process.  System  suffers  f r o m one  a  distinguishing  This requirement  this  only  accuracy.  t r a n s m i s s i o n a much h i g h e r  produced i n the  i n a PCM  A PCM  pulse  t h r e s h o l d s i g n a l power.  -whereas f o r comparable AM  of the  the  peak n o i s e  height.  the  t r a n s m i s s i o n need  reasonable  s e t the  establishes  2.4  second  greater.  bandwidth of V =  2.3  per  to  system t o t r a n s m i t messages of maximum  n  i s n times  inter-  type  of d i s t o r t i o n  or  e r r o r w h i c h c a n n o t be r e d u c e d power.  This i s c a l l e d  the  fact  that there  the  true  signal  m e r e l y by i n c r e a s i n g t h e s i g n a l  quantization noise.  and t h a t a c t u a l l y  to white  decoding,  of t h i s  quantization noise  1 1 AQ A „n = fJ=F=. ~ . — r ' 2 ' n = ^— ^ 2  input signals,  power*  i n watts,  proportional  2.5  to A  Information  This d i f f e r e n c e  as a random n o i s e  very  n o i s e v a r i e s a t random between  0 and l / 2 o f a q u a n t i z i n g s t e p .  of  encoded.  of  noise.  The a m p l i t u d e  the  from  i s a d i f f e r e n c e between t h e a m p l i t u d e  appears a t the r e c e i v e r , a f t e r similar  It results  The r.m.s. a m p l i t u d e ,  o f an n - d i g i t AQ n'+i"—  system  i s then  A  N  , of  g i v e n by  where AQ i s t h e maximum range  in v o l t s T h e  total  quantization noise  a t any p o i n t i n t h e s y s t e m w i l l  be  2 N  , and may  be t a k e n  as  Capacity  The i n f o r m a t i o n c a p a c i t y o f an i d e a l  channel,  limited  (14)  i n b a n d w i d t h t o W , i s g i v e n by Shannon^  C = ¥ log  where S i s t h e a v e r a g e  2  y  ( l + S/N)  as  bits  p e r second,  s i g n a l power and N t h e a v e r a g e  noise  power. Signals with not  information content  be t r a n s m i t t e d t h r o u g h s u c h a c h a n n e l  g r e a t e r than without  this  error.  can Thus  10 for  a c h a n n e l o f b a n d w i d t h ¥ = nW  u p p e r bound t o t h e i n f o r m a t i o n  Q  and S/N = 100 (= 20 d b ) , t h e  r a t e t h a t c a n be t r a n s m i t t e d i s  C = 6.7 n^Q b i t s / s e c . When s u c h a c h a n n e l * i s PCM,  we commonly t r a n s m i t  only  2nWQ b i t s  g r e a t waste binary  From t h e p o i n t efficient  2nWQ p u l s e s  p e r second.  i n information  channel  i sfitted  u s e d t o send b i n a r y p u l s e s ,  p e r second, and t h e r e f o r e  I t i s thus obvious t h a t there  into  a noisy  o f view of i n f o r m a t i o n  t o u s e much s m a l l e r  c o r r e c t these  this  later.  analog  transmission  theory,  S/N r a t i o s ,  medium.  i t w o u l d be more  accept  a  reasonable  and t a k e  steps  However* t h e equipment r e q u i r e d f o r  i s u s u a l l y too complicated. Once i t h a s b e e n d e c i d e d  order  to transmit  information*  o f how t o u s e i t s own l i m i t e d per  is a  c a p a c i t y when a v i r t u a l l y e r r o r - f r e e  number o f e r r o r s i n t h e r e c e i v e d b i n a r y p u l s e s , to  as i n  second t o the b e s t  trying  there  arises  information  advantage.  concerned with A  the secondary  problem  c a p a c i t y o f 2nW^ b i t s  signals.  required to transmit  This  thesis i s i n part  t h e same p r o b l e m .  few o f t h e b a s i c theorems i n i n f o r m a t i o n  t h e o r y and  a p p l i c a t i o n t o PCM s y s t e m s have been d e s c r i b e d .  presented  i n this  chapter  a r e a p p l i e d i n subsequent  i n the e v a l u a t i o n of the proposed framing design  channel i n  Much work h a s b e e n done i n  t o economize on t h e number o f b i t s  speech* music and t e l e v i s i o n  their  t o use a b i n a r y  o f the system.  The i d e a s  chapters, —  scheme and i n t h e  11 3.  A PROPOSAL FOR  3.1  GROUP SYNCHRONIZATION FOR A PCM  Requirements of a S y n c h r o n i z a t i o n  f r e q u e n c y and t h e p u l s e requirement to  i s easily  the decoder p u l l  c l o c k may into  i n the decoder.  a c c o m p l i s h e d by h a v i n g  that  i t s p r o p e r phase o r an o s c i l l a t o r I n e i t h e r case*  pulse  that  yet  quite  the l o c a l  i n the face  relatively  long periods  o f time between  must  e s t a b l i s h and m a i n t a i n  more d i f f i c u l t to s t a r t  in  some way  and  continue  i n transmission  or  digits.  the s y n c h r o n i z a t i o n  the proper pulse  scheme  group t i m i n g , i s  I f i t were p o s s i b l e f o r t h e d e c o d e r  from the coder* group s y n c h r o n i z a t i o n  as t h e y were w o u l d n o t be  s e r i o u s problem, but i n v a r i a b l y * the decoder c i r c u i t starting  high  starting  i t must  up i m m e d i a t e l y upon r e c e i v i n g t h e p u l s e s  transmitted a  to a t t a i n .  that  i n the  systems w i t h  Also  of temporary breaks  The s e c o n d r e q u i r e m e n t *  local  of b i t t i m i n g  c l o c k must be f a s t  i n s e n s i t i v e to i n t e r f e r e n c e .  to operate  This  i s pulled into i t s  schemes, e s p e c i a l l y i n f a s t  rates, i s that  pulses  the f r e q u e n c y of o s c i l l a t i o n i s  The m a i n p r o b l e m i n t h e d e s i g n  synchronization  first  i s shock e x c i t e d  c l o s e l y r e l a t e d to the f r e q u e n c y of the master c l o c k coder.  The  the incoming  c l o c k i n t o synchronism.  be e i t h e r a r i n g i n g c i r c u i t  proper phase.  scheme f o r  the b a s i c pulse r e p e t i t i o n  group t i m i n g  a local  SYSTEM  Scheme  As s t a t e d p r e v i o u s l y * t h e s y n c h r o n i z a t i o n PCM must e s t a b l i s h and m a i n t a i n  SPEECH  or the t r a n s m i s s i o n  i s slow  c h a n n e l a c t s upon t h e p u l s e s i n  t o cause e r r o r s i n t h e t r a n s m i t t e d  s i g n a l and t h e  decoder i s not Now, i n the  able  one  to c o r r e c t l y  would l i k e  most e f f i c i e n t  would s a c r i f i c e  to f u l f i l  a minimum o f t h e  easy to devise  a more e c o n o m i c a l  l e s s t h a n one  3,2  A Proposal  The is  digit  the  The  i n s t a n t s by  range t h a t  can  be  decoded.  in  a m p l i t u d e between two  greater the  than one—half  decoder d e t e c t s  g r o u p of p u l s e s . one  digit  repeated.  the  per  code g r o u p *  the  the  system.  operation.  t o the  successive  g r o u p and  find  the  input  the d i f f e r e n c e samples i s  range of t h e  a minimum o f one  decoder w i l l  amplitude  d e m o d u l a t o r where i t  the  system*  incorrect  decoding operation then s h i f t s previous  successive  resulting  reconstructed  the maximum a m p l i t u d e  scheme  two  maximum  The  o p e r a t i o n s * where n i s the  the  require  waveform i s r e s t r i c t  decoding operation,  Eventually, after  such s h i f t i n g  speech voltage  transmitted  removed f r o m the  n-1  per  thought  or framing  t h a t i t i s o p e r a t i n g upon the  The  digit  I t was  i n a m p l i t u d e between any  h a n d l e d by  is  one  Synchronization  input  i s t h e n c o d e d and  the  It i s  found t h a t would  more t h a n o n e - h a l f  I f , after  c a p a c i t y of  code g r o u p f o r s u c c e s s f u l  vary  method  information*  proposed group s y n c h r o n i z a t i o n  i t does n o t  sampling  signal  per  efficient  purposes.  scheme c o u l d be  timing.  requirements  a method t h a t u t i l i z e s  f o r Group  following.  so t h a t  An  synchronization  group  above  information  code g r o u p f o r g r o u p s y n c h r o n i z i n g that  the  manner p o s s i b l e .  system f o r c a r r y i n g the relatively  e s t a b l i s h the  to a group  process  is  o r a maximum of number o f  c o r r e c t group  digits sequence  and w i l l is  continue  to operate  on t h i s  sequence u n t i l  transmission  interrupted* The  that  the  r e s t r i c t i o n that  input signal  amplitude  i s p l a c e d on the  to the  sampler  b y more t h a n A Q / 2 b e t w e e n any two  of the a l l o w a b l e i n p u t s i g n a l  frequency  3.3  can be  then d e r i v e d  E v a l u a t i o n of the  and  the  signals  amplitude  t o be and  amplitude  amplitude,  A  sampling  allowable. M  is illustrated  the e f f e c t  ,  versus  i n Figure 3 . . 1 .  of the  restriction  t r a n s m i t t e d i t i s necessary to consider  frequency  characteristics  l o u d e s t p e r i o d s * most o f t h e s p e e c h c e n t r a t e d near  successive  Proposal  In order to i n v e s t i g a t e on t h e  then, i s  s h a l l not vary i n  p e r i o d s * where A Q i s the maximum s i g n a l A plot  system,  a single  frequency  frequency v a r i e s with time.  The  of s p e e c h .  power i s n o r m a l l y  component, t h o u g h  In  the  con-  this  peak sound p r e s s u r e s ,  and  t h e r e f o r e t h e peak v o l t a g e s * depend upon t h e f r e q u e n c i e s i n F i g u r e 3 . 2 shows a t y p i c a l  use.  amplitudes, rarely  A , i n various frequency s  exceeded A PCM  low  ( i n ifo  system  frequencies w i l l  anywhere n e a r shows t h a t  designed never  overload.  e v e n t h e new  See  ranges  of a l l l/8—second so t h a t  giving  the  peak  which are  only  intervals).  i t does n o t  overload at  experience high-frequency  A comparison  framing  Appendix 1 f o r d e r i v a t i o n *  components  o f F i g u r e s 3 . 1 and  restrictions, A  f r e q u e n c i e s by t h e p r o p o s e d *  histogram  M  , imposed on t h e  system  are not  3 . 2 high  normally  14  {VOLT$ p-p)  52  Figure  3.1  Amplitude Versus Frequency C h a r a c t e r i s t i c of I n p u t S i g n a l s f o r O p e r a t i o n o f PCM F r a m i n g C i r c u i t  (MAXIMUM %f>ee<iH  I Figure  3.2  Maximum Sound P r e s s u r e s i n V a r i o u s F r e q u e n c y Bands f o r l / 8 Second I n t e r v a l s of C o n v e r s a t i o n a l Speech (Mean o f C o m p o s i t e Voices)« A d a p t e d From R e f e r e n c e 15. ( V e r t i c a l s c a l e a d j u s t e d so t h a t low f r e q u e n c i e s j u s t o v e r l o a d a PCM s y s t e m w i t h a m p l i t u d e range A ) Q  15 v i o l a t e d by  speech s i g n a l s .  g a i n e d and no  information .capacity  However, f o r a t r u e f o l l o w i n g must be in  the system.  systems  consider  emphasis.  The  n o r m a l l y has  3.3  Figure  (a).  This  The  are  i n Figure  3.3,  Versus  exaggerates the amplitudes of the  i n s p e e c h so t h a t t h e r e s u l t i n g  characteristic  i s as shown i n ( b ) .  The  amplitudespeech  s y s t e m a c t s upon t h e s p e e c h s i g n a l s i n t h e  After transmission  usual  and d e m o d u l a t i o n , t h e s p e e c h s i g n a l s  e q u a l i z e d by t h e de-emphasis  manner t o t h e p r e - e m p h a s i s  Speech  as shown i n  E f f e c t o f P r e - e m p h a s i s on t h e A m p l i t u d e F r e q u e n c y C h a r a c t e r i s t i c o f Speech  transmission manner.  illustrated  For  system t h a t uses p r e -  an a m p l i t u d e - f r e q u e n c y c h a r a c t e r i s t i c  higher frequencies frequency  speech t r a n s m i s s i o n  circuit  i s used  i s o f t e n used i n speech  t h a t a r i s e s w i t h i n the system.  situationis  pre-emphasis  the  Suppose t h a t p r e - e m p h a s i s  i s a method t h a t  any  been  lost.  e v a l u a t i o n of the p r o p o s a l ,  considered.  to reduce noise  example*  Thus i t seems t h a t f r a m i n g has  circuit  circuit.  The  i n e x a c t l y the resulting  inverse  amplitude-  !6 frequency c h a r a c t e r i s t i c that  i s shown i n (d) and  i s i d e n t i c a l to  o r i g i n a l l y p r e s e n t e d to the pre-emphasis  speech s i g n a l s  are not a l t e r e d  and de—emphasis  processes.  i n any way  But note t h a t  the  system between t h e p r e — e m p h a s i s  has  a more o r l e s s  r e d u c e d by t h e de-emphasis  in  particular,  efficiency  by t h e  pre-emphasis  any n o i s e  the e f f e c t reduced.  process.  F o r a PCM  of q u a n t i z a t i o n noise  Thus* p r e — e m p h a s i s  enters  circuits  and  speech  system  c a n be  increases  the  noise.  i n a d d i t i o n to pre—emphasis, the proposed framing  scheme i s u s e d , i t i s o b v i o u s t h a t  the higher  frequencies i n  s p e e c h c a n n o t be p r e - e m p h a s i z e d t o t h e same e x t e n t of  that  and de-emphasis  of the system by d e c r e a s i n g the  If,  Thus t h e  continuous spectrum throughout the passband  is  substantially  circuit.  t h e i n f o r m a t i o n c o n t e n t o f t h e s p e e c h i s t o be  Thus, pre-emphasis  c a n n o t be  as b e n e f i c i a l  i f none sacrificed.  as i n t h e f i r s t  case  and t h e s y s t e m must o p e r a t e w i t h a g r e a t e r amount o f n o i s e i n the  received On  signal.  the b a s i s  o f a c o m p a r i s o n o f t h e two  w i t h t h e maximum p r e - e m p h a s i s  and an e n t i r e l y  cases:  the  system  s e p a r a t e means o f  f r a m i n g , and t h e s y s t e m w i t h p a r t i a l p r e - e m p h a s i s  and t h e  p r o p o s e d f r a m i n g scheme, an e v a l u a t i o n o f t h e f r a m i n g p r o p o s a l can  be  carried The  of  the noise The  that  out.  evaluation i s carried that first  results  o u t on t h e b a s i s  i n t h e two  case y i e l d s  cases.  the f o l l o w i n g  group s y n c h r o n i z a t i o n i s c a r r i e d  of a comparison  out by  results.  Assume  some o t h e r means,  * The n o i s e i n a PCM s y s t e m may be assumed t o be e n t i r e l y due t o q u a n t i z a t i o n , s i n c e t h e s i g n a l power c a n a l w a y s be i n c r e a s e d to reduce a l l other types of noise to n e g l i g i b l e v a l u e s .  17 a c o n s i d e r a t i o n o f w h i c h may be i g n o r e d . is  then  found. is  signal  d e c o d e d and a c e r t a i n amount o f q u a n t i z a t i o n n o i s e i s A f t e r de-emphasis* however* t h e a m p l i t u d e  g r e a t l y reduced.  The  The r e c e i v e d  This e f f e c t  i s illustrated  n o i s e power i n t h e p a s s b a n d i s t h e n  numerical  i n t e g r a t i o n method* and t h e n  o f an e q u i v a l e n t  s y s t e m whose n o i s e  of the n o i s e  i n Figure  c a l c u l a t e d by a  3.4*  simple  equated to the noise  amplitude  i s constant but  f o r w h i c h t h e number o f d i g i t s p e r code g r o u p , n^ i s unknown^ S o l v i n g f o r n^ y i e l d s an e q u i v a l e n t The than The  The bits  s e c o n d case  leads t o another v a l u e , n ,  characteristic  i n Figure  Figure  this  time i s g r e a t e r .  case  i s also  3.4. of n i s then  p e r code g r o u p g i v e n up b y t h e t o t a l  The  to the proposed  calculations will  t h e number o f  information  capacity  s y n c h r o n i z a t i o n scheme.  now be c a r r i e d  out.  Refer to  3*4. L e t N Q be t h e t o t a l  h — d i g i t PCM is  of t h i s  d i f f e r e n c e i n the value  of the b i n a r y channel  smaller  2  b e c a u s e t h e amount o f n o i s e  frequency  illustrated  p e r code g r o u p f o r  s y s t e m w i t h t h e same n o i s e power.  the f i r s t noise  t h e number o f d i g i t s  q u a n t i z a t i o n n o i s e power o f an  s y s t e m w h i c h u s e s no p r e — e m p h a s i s .  t a k e n t o be t h e s q u a r e o f t h e r.m.s* n o i s e  I t was shown i n s e c t i o n 2*4 t h a t A  n  Noise  amplitude,  n  =  ^  t  2  n «  A » n  i s g i v e n by  ^0 A  power  ^0 o  r  N  0 =  3 .  2  2(n+l)  T h i s n o i s e i s u n i f o r m l y d i s t r i b u t e d o v e r t h e f r e q u e n c y band  18  (Noise PtvtR PCR  UNIT  6 A N O V < / | O T » A  Wo  .31 Vo  ."Jo Vo .13 Vo .08 Vo  Figure  3.4  Power S p e c t r u m Systems  o f Q u a n t i z a t i o n N o i s e i n V a r i o u s PCM  VQ  - system w i t h o u t  v,  - s y s t e m w i t h maximum p r e - e m p h a s i s speech spectrum  v  - s y s t e m w i t h p a r t i a l p r e - e m p h a s i s due t o h i g h f r e q u e n c y r e s t r i c t i o n imposed b y t h e p r o p o s e d f r a m i n g scheme  2  ' Note t h a t v-j^ =  V Q U  S  / A Q )  pre-emphasis  2  where A and A a r e g i v e n s m 6  and v  2  =  i n Figures 6  v ( A 0  S  / A  a l l o w e d by  2  M  )  3.1 and 3.2.  19 WQ  ( = 4 k c ) so t h a t t h e n o i s e power p e r u n i t  constant  throughout.  but  now  ¥  the n o i s e  o f t h e same n - d i g i t  a r e imposed b y f r a m i n g  t o t a l n o i s e power and v^  V o  o =  u s i n g t h e maximum amount o f p r e - e m p h a s i s  restrictions  a t any f r e q u e n c y  is  Therefore,  v  Consider  bandwidth, V Q ,  system,  p o s s i b l e ; no  schemes.  Let  i t s n o i s e power p e r u n i t  i s g i v e n i n terms  PCM  be i t s bandwidth,  of V Q by v^ = V Q ( A / A Q ) , S  and t h e r e f o r e  using numerical The  integration  use o f p r e - e m p h a s i s  t h e r e f o r e more t h a n h a l v e d ratio  i s now  i n Figure  equal  3.4.  i n an n - d i g i t  t h e n o i s e power.  t o t h a t o f a PCM  PCM  system has  The s i g n a l  system u s i n g no  to noise  pre-emphasis  n  but  e m p l o y i n g n.^ d i g i t s p e r code g r o u p . » number » t i s f o u n d as f o l l o w s :  This e f f e c t i v e  n  1  _1 _ N  Therefore  0  =  A  0 2 0  *  A  / ( 3 ,  ,  . _ o~2(n -n) 2  2  ^ )  n - n = - \ . l o g ( 0 * 4 8 ) = 0.53 0  digits.  digit  20 When t h e p r o p o s e d f r a m i n g frequency partial unit  components a r e  pre-emphasis  bandwidth, v ,  reduced  restricted  can be and  2  system i s used, the  the  used. total  to amplitude  A ,  and  m  only  Hence the n o i s e power n o i s e power, N ,  are  2  per  not  as much, ^0  V  high  2 =0 V  a n d  N  2 =/  ^0  • 2 ' V  =fjj  d f  (^)  0 Consequently  t h e new  as b e f o r e , and The quality  n  effective  - n = 0.32  2  equivalent  loss  64N  digit  number, n  2  i s not  as l a r g e  digits.  received signal  to the  = °- «  d f  0  c o s t o f the proposed f r a m i n g  of the  2  o f 0.53  scheme i n l o s s  i s t h e r e f o r e seen - 0.32  = 0.21  of  as  digits  per  code  group. O t h e r PCM f r a m i n g by average,  framing  sacrificing  by  intervals  adding  g r o u p , o r the  i n every  c o u l d be last  fewer d i g i t s  or s u b s t i t u t i n g  r a t h e r than  pulse  sacrificed  systems c o u l d c o n c e i v a b l y a c h i e v e  i n favour  a framing  digit  or t h e  information d i g i t the  complexity  code g r o u p .  i n every  of f r a m i n g .  schemes are u n f a v o u r a b l e  code g r o u p on  framing  added a t t h e  pulse  per  end  pulses  at  the frequent  F o r example,  of every  tenth  But,  i t i s apparent  one  code  t e n t h code g r o u p c o u l d  be  that  such  b e c a u s e e i t h e r method, the a d d i t i o n o f  substitution  of a framing  i n a code g r o u p a t f r e q u e n t  o f the  correct  digit  f o r an  intervals,  instrumentation considerably.  increases  21 3.4  Misframing Detection  and C o r r e c t i o n  I f t h e d i f f e r e n c e i n a m p l i t u d e between two s u c c e s s i v e decoded  samples  exceeds  o n e — h a l f o f t h e range  an e r r o r i n : f r a m i n g i s i n d i c a t e d * error i n d i c a t i o n occurs w i l l  discrete  7 digits levels,  illustrates  The c o n d i t i o n s  under  which  now be i n v e s t i g a t e d .  Assume t h a t t h e s y s t e m employing  o f t h e system,  under  p e r code g r o u p ,  consideration  giving rise  t o 128 p o s s i b l e  and a s a m p l i n g r a t e o f 8 k c / s .  t h e time r e l a t i o n s h i p w i t h i n  i s one  F i g u r e 3.5  a code  group.  CORRECT CODE GROUP  2  Z' 2°  BIT  BIT  6  BIT  2  s  SIT  2" 2 BIT  3  BIT  2 " 2'  2°  BIT  BIT  BIT  eo Cooe  SIT  2  s  2  4  filT  6IT  Cadooo  TIME Figure  3.5  Misframing by 1 D i g i t  Suppose t h a t t h e d e c o d e r frame and i n f a c t  i s operating  t i m e t h a n t h e c o r r e c t group* the  true  actual input  on a n i n c o r r e c t  on a code g r o u p  1 b i t later i n  That i s , the decoder  5 6 2 b i t t o be t h e 2 b i t and t h e t r u e  2^ b i t as i l l u s t r a t e d the  i s operating  i nFigure  3.5.  that  6 2 b i t t o be t h e  I t c a n be a r g u e d t h a t i f  s i g n a l t o t h e coder has a slope  + 32 l e v e l s p e r s a m p l i n g p e r i o d , t h a t  assumes  of l e s s than  i s , t h e sample  o f two c o n s e c u t i v e s a m p l i n g i n t e r v a l s d i f f e r  amplitudes  by l e s s t h a n 32  levels* signal  an  error v i l l  crosses  situation  the  64  be  level  is illustrated  t-evsu  i n d i c a t e d i n the  1  during  the  i n Figure  sampling p e r i o d .  input The  3.6.  IN STRUTS  L^-"*  d e c o d e r i f the  >  >  >  v ^  I2S  i  h Figure  3.6  I n p u t S i g n a l T h a t C r o s s e s the 64 L e v e l W i t h o f L e s s Than 32 L e v e l s / S a m p l i n g Period  For  example, suppose the  second sampling levels  period. and  instants i n Figure  respectively.  p e r i o d and  the  The  The  slope  s i g n a l crosses  3.6  to  the  least  significant  on  the  code g r o u p 1 d i g i t  numbers w o u l d be  the  64. l e v e l  code g r o u p .  w o u l d t h e n be on w h e t h e r the  12  and  first  o f 70  from l e f t  digit*  I f the  later  where _  f r o m the the  e i t h e r 80 digit  levels  and  and 40  levels/sampling during 40  the are  to r i g h t ,  sampling 1000110 the  most  operating  c o r r e c t group  the  d e c o d e r as 0001100  and  first  numbers, the  o r 81  i n the  70  first  d e c o d e r were  i n d i c a t e s the  In decimal  a t the  and  reading  i n t e r p r e t e d by  101000_respectively*  are  i s t h e n 30  binary representations  OlOlOOOrespectively,  following  amplitudes  Slope  digit  i n the  decoded  values  r e s p e c t i v e l y , depending  f o l l o w i n g code g r o u p i s 1 or  0.  23 The  situation i s illustrated  IO  1 0 0 0  i n Figure  =•»•  AO  T 1 0  1 1 0 0  1  3.7,  O O  VALUES  0 I NCoRKacTLV occooso  J2  —  *  i  TIME.  Figure  3.7  D e c i m a l Numbers 70 and 40 I n c o r r e c t l y Decoded as 12 and 80 o r 81  Because t h e decoded v a l u e s  d i f f e r b y e i t h e r 68 o r 69, both;  o f w h i c h a r e g r e a t e r t h a n 64, t h e f r a m i n g  circuit  d e c o d e r i s o p e r a t i n g upon t h e i n c o r r e c t p u l s e decoding  operation A  the  g r e a t e r t h a n 32 l e v e l s during  and t h e i n p u t  the sampling p e r i o d .  detects  operation  that the  Hence, t h e  later  i n time,  s i m i l a r argument c a n be made f o r t h e s i t u a t i o n where  i n t h e above case b u t where t h e s l o p e  circuit  group.  i s s h i f t e d t o a group one d i g i t  d e c o d e r i s o p e r a t i n g upon a p u l s e  level  detects  of the input  later  removed as  signal i s  s i g n a l does n o t c r o s s t h e 64  Again,  the e r r o r i n framing  t o a g r o u p one d i g i t  group one d i g i t  the decoder  and s h i f t s  framing  the decoding  i n time.  T h e r e a r e two c a s e s , when t h e d e c o d e r i s o p e r a t i n g on a frame one d i g i t error w i l l  later  be i n d i c a t e d .  i n t i m e t h a n t h e c o r r e c t one, when no These c a s e s a r i s e when t h e i n p u t  s i g n a l does n o t c r o s s t h e 64 l e v e l  and has a s l o p e  + 32 l e v e l s p e r s a m p l i n g p e r i o d , and when t h e i n p u t the  64 l e v e l  and h a s a s l o p e  per  sampling p e r i o d .  of less signal  than crosses  o f between + 32 and + 64 l e v e l s  I t i s p o s s i b l e t o reduce the l i k e l i h o o d o f  r n i s f r a m i n g due t o t h e above c a u s e s is  established  amplitudes  as t h e z e r o s i g n a l  i f t h e 64 l e v e l level.  i n s p e e c h waveforms a r e t h o s e  t h e maximum o r t h o s e within + 32 l e v e l s Furthermore,  o f t h e system  The most less  probable  than  one-half  of the zero s i g n a l  level.  t h e most proba,ble t i m e between z e r o a x i s c r o s s i n g s (16)  in  speech  The  i s about  combination  rnisframing  by  1 millisecond  o f t h e s e two f a c t o r s  f o rindication  one—half m i l l i s e c o n d *  All  since  zero a x i s  possible  Similar  indication  a r e summarized  D I G I T S  In f a c t , the b y one d i g i t i s  crossings are l i k e l y t o  arguments c a n be a p p l i e d  by more t h a n one d i g i t .  _  rnisframing  INCXJT S I G . N A I _ CiOfiS NOT  _ L E V E L S A N O MAS ^.UOPIS O P _ LEVGL^/^AMPLINfe PSRIOO  ^, L E V E L S A N O M A S <~,UO P£ OF_  UEVCLsAflMPLlN6  ft PPROXIM A T £  CieoSS  PftOB*fcL£  PB4IOO  T t M C RJK. £ R f t O A INDICATION  SLoPe  (msec  Laytu.?,  64  0<ft<3Z  2  32,64,%  <><|s/< lb  32,64,96  3  /6,31,46,64,50,  0</s/<8  / 6 , 3 2 , ASM,  64  W<|ft|<*4  'A  /6</s/<64  '/*•  8 0 ff</s/<64  9 6 , 112.  6  T a b l e 3.1  error  i n T a b l e 3.1.  t  5  have  t o cases of  Conditions f o r framing  INPUT SIG-NRL c«os.s.es,  LEVELS  4  permanent  s i t u a t i o n s f o r rnisframing b y one d i g i t  rnisframing  B Y  of  that  millisecond.  been d e s c r i b e d .  MISFRPIMING  then ensures  one d i g i t w i l l be h i g h l y u n l i k e l y .  most p r o b a b l e t i m e  occur every  o r 8 sampling p e r i o d s .  48,fT6,64,72,  8/6,24,32,40, o<l$IU 4 5 , 5 6 , 64, 72,  4,8,11,1^20,.  o</s/^a 4 8,/2, 16,20^ Z</s/<t4  8, /6, *4,32,4o,  /s  4*</s/<64  }  2,4,6,8,/o,  K(*I<4A  C o n d i t i o n s and A p p r o x i m a t e P r o b a b l e Misframing Error Indication  /a  Times f o r  )  25 It detection is  i s apparent i n the  t h a t the time  required  cases of misframing  somewhat l e s s t h a n t h a t r e q u i r e d  m i s f r a m i n g b y one  d i g i t because  for error  by more t h a n one to detect  digit  an e r r o r o f .  o f the g r e a t e r  number o f  possible  conditions  under which niisframing e r r o r s  In f a c t *  f o r t h e c a s e s o f m i s f r a m i n g by more t h a n t h r e e  misframing  errors  subsequent  sampling p e r i o d *  detection  are d e t e c t e d  as o f t e n  as n o t w i t h  Thei a v e r a g e  i s t h e n r e d u c e d t o one  are d e t e c t e d *  time  sampling  digits,  each  for error  period  or l / 8  milli-  second* The  total  synchronization  time  i s the  f o r achieving sum  correct  of the times f o r f r a m i n g  i n d i c a t i o n and e r r o r c o r r e c t i o n .  Each  15 p u l s e  3*8  times  s i n g l e pulse  as shown i n F i g u r e  time d u r i n g  group  shifting because  error  operation  i n a d d i t i o n t o the  which the a c t i o n of the decoder  i n h i b i t e d , the a c t i o n of the f r a m i n g e r r o r d e t e c t i o n be  i n h i b i t e d f o r 1 group  amplitudes  time*  since  of the r e c o n s t r u c t e d  a comparison  -«  CORRECT  cooe  CRcuP  —*• <-  •<— Ffs&fMEJO COOE  1  ' NEW  v I-* ) 1  circuit  sample i s m e a n i n g l e s s *  Afew  ASSUMED  CoOc  Gfitovp  MtseaftMi«G ACTION OF oecoost  flSSUMCO  —"> oe.TEarion  INHIBITED  >Figure  3.8  Time R e q u i r e d F o r M i s f r a m i n g E r r o r Shifting  must  assumed code  —•>  Co/VieCTCOO£G«OU0  QS>oup—*  is  of the  sample f r o m t h e new  g r o u p w i t h the p r e v i o u s r e c o n s t r u c t e d  requires  Indication  and  26 The  action  arrival  o f the f r a m i n g e r r o r d e t e c t i o n c i r c u i t  o f t h e n e x t assumed code g r o u p .  to achieve c o r r e c t If later digit*  such t h a t  digits.  decoder  c a s e one It  by  inhibiting  correct  the a c t i o n of the decoder  that,  by one  rnisframing  by  An  digits  of the proposed  o r f r a m i n g scheme f o r a PGM It  i s economical  and  speech  relatively  incorporated  i n the decoder.  rnisframing  f o r one  unless*  six digits*  i n correct  framing. faster  p u l s e time  This results  from  than the  rnisframing times f o r  digits. p u l s e group system  synchronization  has now  been d e s c r i b e d .  simple to i n s t r u m e n t .  c h a p t e r d e s c r i b e s the i n s t r u m e n t a t i o n of the  proposed  by  are l o n g e r than the i n d i c a t i o n  a g r e a t e r number o f  outline  is  rnisframing  on the a v e r a g e , i n d i c a t i o n t i m e s f o r  o r two  This  digits  framing i s achieved  by a d v a n c i n g t h e a c t i o n o f t h e d e c o d e r . fact  one  the a c t i o n of the  rnisframing  action results  i s apparent that  by  two  Thus, t h e d e c o d e r  happens t o be  shifting  digit  pulse time.  p u l s e time r e s u l t s i n f u r t h e r  of c o u r s e , the decoder  one  rnisframing  f o r one  In g e n e r a l * then* i n h i b i t i n g  f o r one  i n which  i t is  a c t i n g upon a group  group*  required  the a c t i o n of the decoder i s  i s inhibited  i n the decoder  removed f r o m t h e c o r r e c t b y two  group,  i s indicated  i t s operation  action results  time  i s o p e r a t i n g upon a code g r o u p  than the c o r r e c t  When an e r r o r  total  on  a p p r o x i m a t e l y 3 msecs.  framing i s , at worst,  the decoder  i n time  The  resumes  scheme  Experimental test  f r a m i n g scheme are g i v e n i n C h a p t e r  5.  The  next  as  results  o f the  27 4.  This  chapter  c o n s t r u c t e d PCM  d e s c r i b e s t h e d e s i g n and o p e r a t i o n o f t h e  system.  Since  u n d e r t a k e n by the author described f i r s t . are  SYSTEM DESIGN  the m a j o r i t y o f the d e s i g n  was on t h e d e c o d e r , t h e d e c o d e r i s  The o p e r a t i o n and t h e c i r c u i t s  of the decoder  d e s c r i b e d , f o l l o w e d by a d e s c r i p t i o n o f t h e g r o u p  zation coder  A brief  circuits. concludes The  ranging  synchroni-  d e s c r i p t i o n of the o p e r a t i o n of the  the chapter.  PCM s y s t e m  i n frequency  c o n s t r u c t e d was d e s i g n e d  t o handle  signals  f r o m a few c y c l e s p e r s e c o n d t o 4000 c p s .  The  sampling  i s carried  per  second.  A 7 digit  out a t t h e N y q u i s t  r a t e o r 8000  code i s employed p e r m i t t i n g an  times  amplitude  7 range o f 2  = 128 l e v e l s , more t h a n  applications. the  The p u l s e g r o u p f r e q u e n c y  pulse r e p e t i t i o n frequency  code p u l s e s  least  significant  The decoder coder  coder  4.1  i n time  8000 cps and The  where t h e o r d e r o f  g r o u p i s f r o m t h e most s i g n i f i c a n t t o  digit.  i s one o f t h e c i r c u l a t i n g  is essentially  one o f t h e p u l s e  and decoder are f u l l y  s u p p l i e d by t h r e e  i s then  signal  i s 7 x 8000 = 56,000 c p s .  are t r a n s m i t t e d s e r i a l l y  t r a n s m i s s i o n i n any p u l s e the  adequate f o r v o i c e  count  transistorized  12v s t o r a g e  pulse  type  type.  and t h e  Both the  and o p e r a t e  on power  batteries.  The Decoder 4.1.1  The B a s i c D e c o d e r  Circuit  o In order  to s u c c e s s f u l l y handle  a b i n a r y code, the d e c o d e r  28 must be a b l e and  t o produce a s e r i e s  s t o r e them e i t h e r  series.  of b i n a r y weighted  as i n d i v i d u a l v a l u e s  In the design  b i n a r y weighted values  of the decoder  o r as a sum o f t h e  i t was d e c i d e d  sequence, f o r a f i x e d  pulses  on a c a p a c i t o r .  length of time.  A coincidence  The r e s u l t i n g  g a t i n g arrangement  i s used t o determine the c o r r e c t current  t o be t u r n e d  on.  CQ3  CGI Figure  using  and a p u l s e  regenerator  circuit  binary  and s t o r e d as a  d e r i v e d f r o m a count-*down-by-seven c o u n t e r  The b a s i c  currents  w h i c h were t u r n e d "on",  w e i g h t e d amounts o f c h a r g e a r e t h e n summed voltage  t h a t the  i n the form of b i n a r y weighted  w o u l d be p r o d u c e d b y c u r r e n t g e n e r a t o r s in  values  i s illustrated  generators  i n F i g u r e 4.1.  CGT  4.1  Basic  Circuit  o f the Decoder  A s s u m i n g t h a t t h e d e c o d e r i s o p e r a t i n g upon t h e c o r r e c t pulse time  group o r frame, t h e c u r r e n t g e n e r a t o r s sequence f r o m l e f t  to r i g h t  whether or n o t the p a r t i c u l a r Each current generator, current to flow  i n Figure  code p u l s e  when t u r n e d  f o r a fixed  are turned  on i n  4.1 a c c o r d i n g t o  i n the group i s p r e s e n t .  on* a l l o w s  time i n t e r v a l ,  a pre-determined  thereby,  allowing a  29 fixed  charge to f l o w  exception  o f CGI,  charge of the capacitor value  thereby  quantized After  allows  on  at the gate  into  w h i c h was  discharges  closes, preparing  presented  the  the The  t o the  current  c l o s e d d u r i n g the  into C to  the  of  final  code group i s t h e n p r o p o r t i o n a l  sample a m p l i t u d e  charge to flow  the  one-half  to flow  c y c l e o f o p e r a t i o n o f the  same t i m e ,  then  allows  a b i n a r y weighted s e r i e s .  C a f t e r one  input  one  the  Moreover, w i t h  current generator  producing  a charge t r a n s f e r gate and  capacitor.  each c u r r e n t generator  previous  of v o l t a g e  to the  i n t o the  coder.  generator.;, c y c l e opens  subsequent c i r c u i t s  and,  some r e f e r e n c e v a l u e .  decoder c i r c u i t  The  for  another  was  carried  cycle. The beginning  design  with  limitations  o f the b a s i c d e c o d e r c i r c u i t  a c o n s i d e r a t i o n of the  o f the t r a n s i s t o r s u s e d .  primarily for their reference voltage c h o s e n t o be resistors, 10 v o l t s  the  volts.  ensuring  Then, the  t h a t the  saturated  a t any  Now, represent  128  To  switching  5 volts,  voltage chosen  characteristics.  capacitor i s discharged  permit  from + 4 t o voltage  and  2N1309's were  reasonable  t u r n on p u l s e s were d e s i g n e d  c h o s e n t o be  accurate  to which the  i n height,  i n width. was  —12  favourable  current  6 volts,  size  t o be and  current generators  The  was  emitter negative  pulse  4 microseconds  range a v a i l a b l e i n the  f r o m — 12 v o l t s  out  capacitor  to - 7 v o l t s ,  t r a n s i s t o r s were  thus  not  time.  s i n c e the  entire voltage  l e v e l s , the  to 1 l e v e l  or  range o f  c a p a c i t o r v o l t a g e was =  39 m i l l i v o l t s .  The  5 v o l t s was r e q u i r e d to minimum  to be  possibl  30 value  c a p a c i t o r C was •*• t h r o u g h the c u r r e n t  of the  currents value  o f C was  f i x e d by  the  sum  generators.  I  o f the  T h a t i s , the I  s u c h as t o e n s u r e t h a t the  currents  co minimum would  co not  alter  during  the  any  voltage  pulse  the  c a p a c i t o r by more t h a n 18.5  group p e r i o d .  X^co'  c>  on  5  (  1  3  2  9  *  5  m  s  e  Hence c  _ 7(2  )  6  (39 x  v  maximum p o s s i b l e v a l u e  o f t h e maximum p e r m i s s i b l e on,  i t was  voltage  on  permitted  o f C was  x  C was  one—half  on  C or  2.5  volts*  max  QQQ  (4 tisec)  mum  power r a t i n g  c h o s e n t o be  turned  voltage  range  the v a l u e  X  1  Q  -3  be  )  (  4  x  10~ ) 6  2.5  0*07 [if  of C G I would not  C then f i x e d  basis  the  ~ x  = 0.48  o f C was  the  such t h a t  of t h e  = 480  value  \if  s»'.048  9  Hence  2.5v  The  3  When C G I was  enough c u r r e n t  i n c r e a s e d by  10" )  d e t e r m i n e d on  r e q u i r e d to supply  IC  the v a l u e  10"  in CGI.  current  IO"6)  x 1Q- )(125 x  m 47.7  The  my  10~  9  \if  to ensure  exceeded.  o f the  required  t h a t the  The  maxi-  choice  of  weighting  resistors. For  example, the  current  r e q u i r e d when C G I  i s turned  on  is  4 x  10"°  amps<  The  required weighting  R  Ie  =  X  The  remaining  follows.  (0.07  incoming  by  pulling  oscillations which are  from  the  oscillator  into  the  oscillator  are  suitable  The  bistable  counter,  produced  i n Gate  g e n e r a t o r s are pulses with  the  arrangement  pulses  f o r the  p u l s e s but  a cyclic 1.  then  Turn  o  h  m  S  t  R.  The  converted to resulting  i n the  pulse  i n the sine-wave square  p i p s are  waves  then  count-down-by-  the p u l s e group  frequency.  to various c o l l e c t o r s  sequence o f s e v e n  as  establish  frequency  phase.  of  the  gating pulses i s  on p u l s e s f o r the v a r i o u s c u r r e n t  f o r m e d by g a t i n g t h e  r e g e n e r a t e d p u l s e s from i s such t h a t  sequence of the  i s determined  resulting  i s independent by  seven  r e p e a t e r , i n Gate  t h e h e i g h t o f the  current generators  the w i d t h  they  counter with a  connections  8  regenerated  same t i m e ,  arrangement which e s t a b l i s h e s By  >  i s described b r i e f l y  pulse r e p e t i t i o n  a bistable  2  Decoder  decoder  then d i f f e r e n t i a t e d .  3  are b i n a r y m u l t i p l e s of  code p u l s e s a r e At  1  10"" )(2.5)  an  employed t o t r i g g e r seven  x  =  b  resistors  or r e p e a t e r .  m a i n t a i n the b a s i c  decoder  The  l  o p e r a t i o n o f the  regenerator and  6  O p e r a t i o n of the  The  is  (6 - 0 . 2 ) ( 4 x I O " )  =  weighting  4.1.2  The  resistance  the w i d t h  turn o  o f the g a t i n g of the  repeater  pulses. Thus, the  output  from  Gate  2  2 i s a sequence o f t u r n  on  Cooe  LEWIS  I_OIAJ  C3 Y4  F i g u r e 4.2  B l o c k Diagram o f D e c o d e r  33  pulses  of p r e c i s e h e i g h t  to  the  code p u l s e s  is  u s e d t o t u r n on  sample  amplitude During  1,  the  charge  transfer  presented the  of the  interval  6 to prepare  decoding  cycle.  coder  Lewis g a t e .  order  This  the  entire  4, The  sequence  interval  6 of the  The so  following  on  on  Gate  charge any  as  cycle,  originally during  following  is transferrred  C-j, t h e n ,  a m p l i f i e d as  decoding  of  that  i s discharged  the v o l t a g e  and  a  i s also transferred.  c h a r g e from the  voltage  and  output  interval  sample a m p l i t u d e  i t f o r the  pattern  C-^.  d u r i n g the  is filtered  to  i s a step f u n c t i o n . the  desired  o p e r a t i o n are  audio  given  A-2.11. above d e s c r i p t i o n , t h r e e  to f a c i l i t a t e  circuit  G a t e s 1 and  current  generator,  pulses  the  Sample waveforms o f the  I n the in  i n pulse  current generators  i s s t o r e d i n C^.  interval  waveform on  i n Figure  repeater.  e s t a b l i s h e d by  reconstructed  the  output.  as  7 to i n t e r v a l  c o d e d by  The  to the  identical  i s t r a n s f e r r e d t o C^.  f r o m CG7  Thus, f r o m i n t e r v a l  the  7,  i s open d u r i n g  charge r e s u l t i n g  by  and  i s r e c o n s t r u c t e d on  interval  During  width  appropriate  stored i n  gate  the v a l u e  and  f o r the  the  2 were and  explanation.  I n the  combined  one  separate  d e l a y was  i n t r o d u c e d between the  generator  gates  the  a monostable p u l s e  generator,  is  the  used to operate  Lewis  into  gates  charge t r a n s f e r gate  to o f f s e t  details  PG1, gate.  ignored,  final  decoder  gate,  one  f o r each  were u s e d t o p r o d u c e  and  discharge  repeater  delay  were  and  i n counter  the  the  circuits.  A  current  circuits.  triggered during  Finally,  interval  4,  4.2  O p e r a t i o n of Framing  Circuit  I n o r d e r f o r the g r o u p circuit  to operate  amplitudes If  of two  the d i f f e r e n c e  amplitude  range  difference range  The illustrated  digit  interval  7 by  n o t h i n g i s done.  t o a new  digit  frame one  o f the r e q u i r e d  v o l t a g e s on 0^  a  n  d  C^  r e g a r d l e s s of the p o l a r i t y  amplitude  range  circuitry is  a r e compared d u r i n g t h a t produces  of the  thereby, s h i f t i n g firing  the iroltage  a negative  of the d i f f e r e n c e *  circuits.  The the  o u t p u t and The  output  gated  to  output  i s a p p l i e d to a Schmitt t r i g g e r  that  a t a v o l t a g e c o r r e s p o n d i n g to o n e - h a l f the  a p u l s e i s produced  The  i n time.  i s then gated to eliminate  proper t i m i n g i n subsequent  set to f i r e  operation i s  later  u n d e s i r a b l e p o r t i o n s o f t h e v o l t a g e comparator  is  square  o p e r a t i o n i s d e s c r i b e d as  a v o l t a g e comparator  o f t h e v o l t a g e comparator  amplitude  r e a c h i n g the  decoding  o f t h e v o l t a g e comparator  ensure  I f the  i s that the e n t i r e  The  compared*  than o n e - h a l f of the  t h e r e b y p r e v e n t e d from  i n F i g u r e 4.3.  The  i s less  p i p from the d i f f e r e n t i a t e d  b l o c k diagram  follows.  o p e r a t i o n s t o be  i s g r e a t e r than o n e - h a l f the  one  and  result  s h i f t e d by one  output  i n amplitude  system,  The  i t i s o n l y n e c e s s a r y f o r the  successive decoding  o f t h e system*  wave i s i n h i b i t e d counter.  successfully,  i n amplitude  o f the  s y n c h r o n i z a t i o n or framing  system.  that  I f the  inhibits  one  Schmitt t r i g g e r pip into  the  the o p e r a t i o n o f t h e d e c o d e r by  of the Schmitt t r i g g e r comparator  also  inhibits  fires,  counter, one  digit.  the a c t i o n  c i r c u i t , w h i l e the s h i f t i n g  occurs.  of  \  Lew/is  ^  GATE  c.  OsClLLflTtrt  VOLTAGE COMPARATOR.  iNHiSiT GEN £RfflTD&  PG3  INTERVAL.  Co —  G/VTING  DELAY  P  U  L  S  E  IN M iiil T  Pot.se  GeMClMToK.  PG2.  F i g u r e 4.3  PG4-  B l o c k Diagram of Framing C i r c u i t s  INHIBIT GRTE  COUNTER.  Various pulse generators operation.  Because  undesirable  until  to produce trigger  by  and  gate  inhibiting  i n Figure  inhibits  i s used  A built  brief  interval  a pip into the  6. the  PG3  the  comparator i s  i t was  (PG2)  out  by  necessary  delaying a  i s used  counter,  to  PG4  produce  is triggered  a c t i o n o f the v o l t a g e  comparator  BG2.  t i m i n g waveforms f o r t h e  framing  circuits  are  shown  A-2,12.  coder  Coder  to convert analog  by H a f e r and  description  signals  into  7 digits  i s described i n his thesis ^  i s given  fl  GATE  SWMITT  *MPL)F»&R  I  B  JL GATS'  2.  F i g u r e 4.4  .  of  PCM  Only  a  here.  D/ooe IN  the v o l t a g e  gating pulse  to i n h i b i t  O p e r a t i o n o f the  4.3  from  i n the 7th i n t e r v a l ,  p u l s e d e r i v e d from  The  was  late  the diode  the p u l s e t h a t by PG3  an o u t p u t  are r e q u i r e d to c a r r y  c Jl  R CIRCUITS  B l o c k Diagram of  Coder  i_r  VoLJP,e,£ Oove,ue.R  37 The circuits, is  b l o c k diagram  is illustrated  applied  to the  6 microseconds. it  coder, diode  signal AQ/2  gate  from A  at  B.  where A Q i s t h e maximum  i n p u t sample p u l s e a m p l i t u d e  the Schmitt t r i g g e r  fires  and  an o u t p u t  which expected  exceeds  code p u l s e i s  produced.  At the  a positive  p u l s e of f i x e d h e i g h t AQ/2 at C , which i s s u b t r a c t e d  from  same t i m e , t h e  for  amplifier  i s a p p l i e d to a Schmitt t r i g g e r Q  I f the  signal  1 samples the a m p l i t u d e  inverted  at a voltage A /2.  level.  When an a n a l o g  A f t e r p a s s i n g t h r o u g h the b u f f e r  output  set to f i r e  c o d e r , e x c l u d i n g the t i m i n g  i n F i g u r e 4.4.  emerges u n a l t e r e d a t A and The  is  of the  t h e o u t p u t a t B.  not exceed  AQ/2j  the  Schmitt t r i g g e r  The  output  on, u n a f f e c t e d by t h e  produces  I f t h e i n p u t sample p u l s e a m p l i t u d e S c h m i t t does n o t f i r e  code o u t p u t p u l s e n o r t h e p o s i t i v e produced.  also  of the b u f f e r  and  neither  does  the  pulse of h e i g h t AQ/2 i s amplifier  at B i s then  passed  s u b t r a c t o r , to the v o l t a g e d o u b l e r  amplifier. The  output  o f the  subtractor i s applied  d o u b l e r a m p l i f i e r where i t i s i n v e r t e d The  pulse i s then a p p l i e d The  charge  to the  on a c a p a c i t o r .  A t t h e end  w h i c h up  time  to t h i s  a p p l i e d t o the b u f f e r Diode for  gate  charge  storage c i r c u i t  the v o l t a g e d o u b l e r a m p l i f i e r  and  f o r one  o f one  doubled  storage  stores  to the v o l t a g e i n amplitude.  circuit.  the o u t p u t p u l s e o f  pulse period  as  charge  p u l s e p e r i o d , diode gate  2,  has b e e n c l o s e d , a l l o w s t h e p u l s e t o be amplifier  1 i s closed  once more. at t h i s  7 p u l s e p e r i o d s w h i l e the o r i g i n a l  time  and  remains  closed  i n p u t sample p u l s e i s  38 a l l o w e d to c i r c u l a t e  around  Each c i r c u l a t i o n produces depending first  to  c i r c u l a t i o n produces  the  value  2^,  the the  of 7  code p u l s e o r  trigger  output second  times. space  f i r e s or n o t .  The  code c o r r e s p o n d i n g t o c i r c u l a t i o n 2^,  a code o u t p u t  and  so  the on  corresponding  2°. c o n c l u s i o n of 7 c i r c u l a t i o n s ,  pulse  is inhibited  diode  gate It  icant  digit The  now  and  a new  i s apparent  recirculated  i n p u t sample p u l s e i s t a k e n  output  then* that  the  coder  i s able to  i n s e r i a l f a s h i o n w i t h t h e most  by  produce signif-  first. o p e r a t i o n o f the PCM  been d e s c r i b e d .  m o d i f i c a t i o n s made t o the next  the  1.  a b i n a r y coded  The  output  l a s t c i r c u l a t i o n produces  At the  has  an  loop a t o t a l  on w h e t h e r t h e S c h m i t t  b i n a r y weighted until  the  The  system  i n b l o c k diagram  circuit details  coder  including  form  the  a r e g i v e n i n A p p e n d i x 2 and  chapter d e a l s w i t h the r e s u l t s  of t e s t s  on the  3.  system.  39  5.  5.1  System  The  Performance  system*  satisfactorily. indicated  SYSTEM TESTS  that  as o u t l i n e d  c o d e r and  good q u a l i t y  power r e q u i r e d  1.3  performed  L i s t e n i n g t e s t w i t h a u d i o program s p e e c h t r a n s m i s s i o n was  p r o v i d e d t h a t t h e system was The  i n C h a p t e r 4,  watts  possible,  not o v e r l o a d e d .  i s a p p r o x i m a t e l y 1.4  i n the decoder  circuits) for a total  material  watts  i n the  ( i n c l u d i n g the framing  power c o n s u m p t i o n  of approximately  2.7  watts. A d e l a y o f 0.35 between t h e message  milliseconds  signal  is  o f no p r a c t i c a l  The oscillator  and d r i f t  e r r o r s due  due  to small  the performance  d e c o d e r p r o v e d t o be  d e l a y i s due  changes  mainly  of the  i n room system.  a c c u r a t e and r e l i a b l e .  i n the d e c o d e r t o l e r a t e d  changes  i n the m a s t e r  The clock  f r o m the c e n t r e f r e q u e n c y , t h u s e n s u r i n g  t h a t the d e c o d e r w o u l d  The  The  f o r t h e c o d i n g and d e c o d i n g p r o c e s s e s and  d i d not a f f e c t  f r e q u e n c y o f + 3.9$  by e f f e c t s  observed.  but  importance.  Instability temperature  sampling p e r i o d s  a t t h e c o d e r and the d e c o d e d  u n f i l t e r e d message s i g n a l was t o t h e time r e q u i r e d  o r 2.8  follow  s u c h as t e m p e r a t u r e  small  changes  i n f r e q u e n c y caused  changes.  f r a m i n g scheme p e r f o r m e d more t h a n a d e q u a t e l y and to  rnisframing  when the s y s t e m was  were few.  Framing  errors  occurred o n l y  o v e r l o a d e d t o s u c h an e x t e n t t h a t t h e  input  40 signal  r e s t r i c t i o n s were v i o l a t e d .  required  input  scheme was derived signal  signal restriction  from t h e o r y . restriction as  Figure  tests during correct  not  order  measured b u t  f r a m i n g was  achieved  5«1  The  requirements the  required as  observations  milliseconds.  input  the  time r e q u i r e d  for  with  c o r r e c t f r a m i n g was  was  framing  achieved  In f a c t ,  listening  interrupted disclosed  i n a time  so  short  that  that  noise  due  inaudible.  I  Figure  o f a few  which t r a n s m i s s i o n  t o m i s f r a m i n g was  illustrates  i n Appendix 1 .  o s c i l l o s c p e indicated that  i n t i m e s o f the  the  the  of the  f o r system p e r f o r m a n c e as w e l l  derived  p r o p e r f r a m i n g was  5.1  found t h a t  for operation  s l i g h t l y more s t r i n g e n t t h a n  restrictions  an  I t was  Z  3  4  Input S i g n a l Frequency—Amplitude C h a r a c t e r i s t i c f o r S u c c e s s f u l O p e r a t i o n of the F r a m i n g Scheme  41 The  weakest l i n k  i n the system i s the coder  spite  o f t h e many h o u r s s p e n t  still  lacking i n linearity.  be  due m a i n l y  doubler  5.2  amplifier.  output  (See F i g u r e s 4.4 and A - 3 . 3 ) .  and d e c o d e r r e s p e c t i v e l y .  o u t on t h e c o d e r as t h e i n p u t  codes.  same way —  The t e s t  by u s i n g  coded v a l u e s  by u s i n g a s e r i e s  of the l i n e a r i t y  The t e s t  the r e s u l t i n g  o f t h e d e c o d e r was c a r r i e d  coded p u l s e s  as t h e i n p u t  the d.c. v o l t a g e  i n decimal  was  o f known d . c .  s i g n a l s and o b s e r v i n g  d e c o d e r and o b s e r v i n g the  are thought to  5.2 and 5.3 i n d i c a t e t h e r e s u l t s  on t h e c o d e r  voltages  The i m p e r f e c t i o n s  Tests  Figures  carried  and r e d e s i g n i n g , i s  to the n o n - l i n e a r i t y of the a c t i o n of the v o l t a g e  Linearity  tests  i n modifying  which, i n  out i n the  s i g n a l s to the  outputs.  In both  cases,  f o r m were p l o t t e d v e r s u s t h e  measured d . c . v o l t a g e s . The  n o n - l i n e a r i t y of the o p e r a t i o n o f the coder  t r a c e d to the voltage amplifier  i s less  than  doubler  pulses  signal voltages  5.3  Noise  The g a i n o f t h e  two a t low a m p l i t u d e  c o n s e q u e n c e , when t h e i n p u t circulating  amplifier.  levels.  As a  s i g n a l s are of such v a l u e s  are small i n amplitude,  are g r e a t e r than  they  was  the r e q u i r e d  that the input  should be.  and D i s t o r t i o n  A measure o f t h e d i s t o r t i o n  and n o i s e p r o d u c e d b y t h e  /30  Figure  5.2  Linearity  Test  of  Coder  43  —i—  i  -fe  5.3  1  -5 OUTPUT  Figure  ,—i  -  i  1  -3  -4  VOLTAGE  Linearity  1  o.c  Test of Decoder  i  i  -X  44 s y s t e m was made b y m e a s u r i n g O u t p u t message message  SINE -  signal.  signal using  the harmonic a sine-wave  distortion  as t h e i n p u t  The method i s o u t l i n e d i n F i g u r e  PCM  WAVE  5.4.  MrtRMOMlC DISTORT  GENERATOR.  Figure  of the  5.4  N o i s e and D i s t o r t i o n Measurement  served  o n l y to i n d i c a t e t h a t the d i s t o r t i o n  v o l t a g e was much l a r g e r t h a n the! c a l c u l a t e d q u a n t i z i n g T h i s i s t o be e x p e c t e d i n v i e w  5.2 and t h e  noise.  i n the  imperfections  filtor.  Waveforms  Figure  5.5  illustrates  transmitted  by t h e s y s t e m .  oscillogram  i s the decoded  the  of the imperfections  as shown i n F i g u r e  i n t h e o u t p u t low p a s s  5.4  1  M C T F R  The method  coder l i n e a r i t y  io*  some example waveforms  The u p p e r waveform i n e a c h s t e p waveform b e f o r e  l o w e r waveform i s t h e r e s u l t i n g  waveform, w h i c h waves.  filtered  filtering,  and  v e r s i o n of the step  i s almost i n d i s t i n g u i s h a b l e from the i n p u t  sine-  45  1000 Figure  5.5  cps  3000 cps  Waveforms. O s c i l l o g r a m s o f Decoded and a t O u t p u t o f Low P a s s F i l t e r  S i g n a l s on C  46  6.  A The is  CONCLUSIONS  s e l f - f r a m i n g PCM s p e e c h  results  of t e s t s  system has now b e e n d e s c r i b e d .  on t h e s y s t e m i n d i c a t e  t h a t performance  adequate f o r t r a n s m i s s i o n o f good q u a l i t y The  coder  input—output signal  deserves  f u r t h e r work*  characteristic  levels  causes  and i t i s t h o u g h t  distortion  perfectly  the a c t i o n of the v o l t a g e  decoder  and t h e n o v e l f r a m i n g  and c o r r e c t  Although message c h a n n e l  the framing  scheme was employed on a s i n g l e  d i v i s i o n m u l t i p l e x i n g methods. so t h a t once c o r r e c t  channel,  then,  simultaneously*  speech  emphasized for this  except  signals  i n this  over  framing correct  channel.  channel  i s achieved framing  i n one  i s achieved i n  Framing e r r o r s  f o r framing  purposes*  are only p a r t i a l l y p r e -  circuits  manner as d e s c r i b e d i n C h a p t e r  channels  The s y s t e m w o u l d be  t h e one t h a t i s u s e d  and t h e f r a m i n g  But,  a r e t r a n s m i t t e d by  The maximum p r e — e m p h a s i s i s employed i n a l l  message c h a n n e l s The  achieved  circuitry*  systems where many message c h a n n e l s  channels.  performed  s y s t e m , tVe scheme c o u l d e a s i l y be a d a p t e d t o  designed  all  circuits  g r o u p s y n c h r o n i z a t i o n was  q u i c k l y and e f f i c i e n t l y u s i n g s i m p l e  time  a t low i n p u t  amplifier. The  larger  The n o n - l i n e a r  t h a t much o f t h e d i s t o r t i o n  c o u l d be e l i m i n a t e d by i m p r o v i n g doubler  speech.  are a t t a c h e d t o the decoder  a r e t h e n d e t e c t e d i n t h e same  3.  f o r a l a r g e s y s t e m * where 24 t o 96 o r more message  a r e t r a n s m i t t e d by time  one t r a n s m i s s i o n c h a n n e l *  d i v i s i o n m u l t i p l e x i n g methods  the proposed  scheme i s n o t as  47 advantageous for to  because  of c o n s i d e r a t i o n s  achieving proper framing. sacrifice  such as t h e time  Such a system  can e a s i l y  an e n t i r e message c h a n n e l f o r a more  required afford  efficient  f r a m i n g scheme. The thesis  proposed  i s best suited  self-framing f o r a PCM  speech  s m a l l number o f message c h a n n e l s . i n t h e use o f t h e d i g i t s conserve bandwidth simplicity it  ideal  scheme p r e s e n t e d i n t h i s  and r e l i a b i l i t y  that u t i l i z e s  I n such a s y s t e m ,  i s o f prime  and t o s i m p l i f y  system  economy  concern i n order to  the i n s t r u m e n t a t i o n .  of the s e l f - f r a m i n g  f o r use i n s u c h an a p p l i c a t i o n .  The  scheme makes  a  48 APPENDIX 1  Derivation  of Figure  Figure  For input zero  the  signals. axis  3.1  A-l.l  Assumed Form o f I n p u t  purpose? The  o f a n a l y s i s , assume sine-wave  greatest  crossings.  amplitude  occurring within  centering  about the  Consider the signals ranging are  of the  input  one  axis  input  from zero  sampled a t the  slope  Therefore,  zero  o f the  the  cycle  o c c u r s o v e r an  c o d e r t o be  t o 4000 c p s .  Nyquist rate  The  o f t w i c e the second.  s i g n a l s are  V(t)  in interval  of  = A/2  the  Sin  composed o f  input voice  (10~  form  (27tft)  voic  signal  maximum f r e q u e n c y  Therefore,  microseconds. input  change  the  crossing.  t o the  o r 8000 t i m e s p e r  type  curve occurs at  greatest  b e t w e e n samples i s 1/8000 s e c o n d s = 125  The  Signals  the  interva  ) seconds =  125  49 as  illustrated  waveform t  = 0 ,  a t t = 0,  i t i s necessary  t h a t the t  occurs  i n F i g u r e A—1*1»  The  greatest slope  l / 2 f , l / f ,etc.  to f i n d  the  d i f f e r e n c e i n amplitude  - + 62*5 m i c r o s e c o n d s does n o t  b o u n d a r y c o n d i t i o n on V ( t )  amplitude  t h a t the  at  range A s u c h  exceed A Q / 2 .  and  Hence,  the  i s that  maximum p e r m i s s i b l e s i g n a l  d i f f e r e n c e between two  microseconds apart  example,  between t = -62.5  V ( t ) = A Q / 4 a t t = 62.5  That i s , the  For  i n the  does n o t  V(t) = A /2 m  microsecoiids.  A  amplitude  succesive  samples  by  S i n 2-nf (62.5  =  6  ,  such  125  exceed A Q / 2 i s g i v e n  x 10~ )  M  A /4 Q  or A  m  ~  where f = f r e q u e n c y For  example*  2  in  Ttf/8000  Sin  cps*  a t f = 4000  cps,  A  A  m  The in  results Table  f o r other  A-l.l.  2 Sin  0 .  %/2  =  AQ/2  f r e q u e n c i e s were e v a l u a t e d  and  tabulated  Frequency (cps)  Maximum p e r m i s s i b l e a m p l i t u d e A (p-p)  signal  m  0 -1333  A  0  1500  0.906  A  Q  2000  0.707 A  Q  2500  0.600 A  Q  3000  0.541  A  Q  3500  0.510  A  Q  4000  0.500 A  Q  T a b l e A—1.1  Table of Frequencies Corresponding Signal  o f I n p u t S i g n a l s and Amplitudes  51 APPENDIX 2  C i r c u i t D e t a i l s of the Decoder* The decoder i s , on the whole, a c o l l e c t i o n of transistor The  standard  circuits. c i r c u i t diagrams of the decoder, F i g u r e s A-2.1  to  A-2.9* are s e l f - e x p l a n a t o r y . F i g u r e s A-2.10 and A-2.11 i l l u s t r a t e the t i m i n g waveforms and waveforms of an example decoding  operation.  F i g u r e A—2.12 i l l u s t r a t e s the waveforms  t h a t r e s u l t from d e t e c t i o n of a f r a m i n g  error.  Timing of the c i r c u i t o p e r a t i o n s i s important because of t h i s , i t was  and,  n e c e s s a r y t o d e l a y v a r i o u s waveforms  u s i n g monostable m u l t i v i b r a t o r s *  Delay l i n e s were out of the  q u e s t i o n because of the l e n g t h of d e l a y s r e q u i r e d . Note t h a t the decoder can be a d j u s t e d to d e t e c t the incoming  code p u l s e s a t the l e v e l of o n e - h a l f the p u l s e h e i g h t .  T h i s reduces the e f f e c t of the i n t e r f e r e n c e i n the t r a n s m i s s i o n c h a n n e l , the peaks of which are assumed to be u s u a l l y c o n s i d e r a b l y l e s s than o n e - h a l f the p u l s e h e i g h t . P u l s e t i m i n g i s a c h i e v e d by h a v i n g the incoming p u l l an o s c i l l a t o r i n t o phase*  pulses  But note t h a t the a c t u a l  s y n c h r o n i z a t i o n i s c a r r i e d out by the d e l a y monostable i n F i g u r e A-2.1.  T h i s ensures t h a t i n t e r f e r e n c e i n the t r a n s -  m i s s i o n channel does not a f f e c t the t i m i n g o p e r a t i o n s of the decoder* C i r c u i t d a t a f o r CGI o n l y are g i v e n i n F i g u r e A-2.4. Data f o r the r e m a i n i n g c u r r e n t g e n e r a t o r s , which are i n form to CGI are g i v e n i n Table A—2.1.  identical  52  Current Generator  AND Gate Inputs: Pulse regenerator and counter taps (see Fig, A-2,3):  Emitter R e s i s t o r s (ohms) Fixed Variable  CGI  2, 3 , 6  68  • 100  CG2  1, 4 , 6  168  100  CG3  2,. 4 , 6  500  100  CG4  1, 3* 5  680  IK  CG5  2* 3* 5  1.5K  IK  CG6  1* 4 , 5  3.3K  IK  CG7  2* 4> 5  8.2K  IK  Table A—2,1 Data for Current Generators  To cuaR*MT GehiKHfirroi^  ftND Grt res Q  0-/2*  3SK  i  Resistors: F i g u r e A-2.1  10%  C a p a c i t o r s * 75v. 10%  Input A m p l i f i e r , Delay Monostable  O o  D i o d e s i 1N497 and P u l s e  Generator  UJ  0/2*  lOOff  Resistors I  10$  Figure A-2.2  Capacitors 8 7.5v*.  10$  Driven O s c i l l a t o r . Amplifier and Square Vave Generator  To  CURRENT  Q  G-EM£IKftTOR,  <>^T£S  RND  4 5  2-3  Q  0  9  fool  O ©  Z.exspF R e s i s t o r s : i v * 10$  C a p a c i t o r s J 75v, F i g u r e A-2.3  T r a n s i s t o r s I 2N404  Count-Down-By-Seven  Counter  Diodes:  1N497 VJ1 VJ1  O -/ -0-6 '"497  4-  2A//305 33K  ZA//38/  < ^6  c,  SoopF 5 Q_A^X6 O-AA^fc  /CO >  -O o  R e s i s t o r s : ^w, F i g u r e A—2*4  Current  10%  C a p a c i t o r s . 75v, 1 0 %  G e n e r a t o r CGI and S t o r a g e C a p a c i t o r  C.  Q 0-/2£  3SOK  2A7/38/ Loo  50-w56H -Oo  Resistors* Figure  1°$ 5  C a p a c i t o r s I 75v, 10$  Charge T r a n s f e r  Gate  Resistors. Figure A-2.6  10$  C a p a c i t o r s : 75v, 10$  Discharge  Gate  Resistors?  i w , 10$  Figure A~2»7  C a p a c i t o r s : 75v, 10$  D i o d e s : 1N497  Lewis Gate, V o l t a g e Comparator,  Transistors:  and D i o d e  1N1381  Gate CO  *—O  -/2 X  Co (la) LevyiS  GrPire Puu<,e. GeN&RflTzxi (^6-/)  G  TO  Ffl-bM HS.LA-1 2  .  7 <  ,  27*  *—0-2o£  Ps-4-  Resistors: Figure  £ v , 10$ A-2.8  Capacitors:  75v, 10$  (a) S c h m i t t T r i g g e r  Transistors:  (b) PG1  2N1381  (c) Delay Monostable  Diodes: f o r PG2  1N497 (d) PG2  Ul vO  PC4-Q  F<LoM  ..  PG 3 - r O J h r  2-7K< O o  6  0+4* (a) CoOnT INH161T P>U>-S£ GCNeRATBA (P^"i)  R e s i s t o r s , ^w,  10%  C a p a c i t o r s . 75v. 10%  (6)  ^ / O O f GftT£  INHIBIT  T r a n s i s t o r s ! 2N1381  Figure A-2.9 Pulse Generators*  ( a ) PG3  POLS£  0-20^  -/2* G£A/£AAToK  D i o d e s 1 1N497  (PG4)  (b) PG4  ON o  I 61  SqufUle. wave.  GENERAL*  + 6  INTERVAL  1  F i g u r e A-2.10  I  3  4  5  G  7  C o u n t e r Waveforms and I n t e r v a l s  Defined  62  4  I,  7  7  Cooe  PUL.SE AEGEIVEATOA OUTPUT  4^  91  •  c  2  43-  OIOIOII  F i g u r e A-2.11  91 «  Waveforms on o f 43 and 91  IOIIOII  , C » C 2  3  Due t o R e c e i v e d  Values  63  IN  7  Z  6  0  ON  Cz  V OL.T«^fit ON  OUTPUT  OR  <-J ^  GATE:  8V PG»4  SCHMITT  TRIGCSR _S  ^-  K»  IN»I6IT-  PG3 INHICIT -  PG4-  F i g u r e A—2*12  F r a m i n g C i r c u i t Waveforms Due t o Decoded V a l u e s o f 20 and 91. C o m p a r i s o n C a r r i e d Out D u r i n g I n t e r v a l 7; I n t e r v a l 0 I n d i c a t e s S h i f t  64 APPENDIX  Circuit  3  D e t a i l s of the Coder.  Extensive designed  m o d i f i c a t i o n s were c a r r i e d  and c o n s t r u c t e d by H a f e r ^ ^  operation to the operation  o u t on the c o d e r  t o improve and a d a p t i t s  o f the? d e c o d e r .  There were manyfollowingt  m i n o r changes b u t t h e major changes a r e t h e 1*  The number o f d i g i t s seven* number  This  2*  to  to  t o a 7*1 d e v i c e *  Hafer's  vibrators 3*  twofold  was  circuits of d i g i t s  increased  d i v i d e r was  i n order p e r code  f r o m 48 k c / s  changed f r o m a 6*1  A l s o * most o f t h e d e l a y  lines  used  c i r c u i t were r e p l a c e d b y d e l a y m o n o s t a b l e m u l t i f o r greater  The c i r c u i t to  i n t h e number  clock frequency  56 k c / s and t h e f r e q u e n c y  device in  changes were made i n t h e t i m i n g  The b a s i c  i n the  of o p e r a t i o n *  accommodate t h e i n c r e a s e  group*  increase  f r o m 64 t o 128* and r e q u i r e d a  i n accuracy  Extensive  changed f r o m s i x t o  change r e s u l t e d i n a t w o f o l d  of l e v e l s ,  increase  p e r c o d e g r o u p was  voltage  adapt the c i r c u i t  stability  and  accuracy.  l e v e l s were changed and some were tooperation using  standard  added  12 v o l t  storage b a t t e r i e s * 4*  A second Schmitt the  effects  height 5*  t r i g g e r was a d d e d i n c a s c a d e t o r e d u c e  o f t h e "maybe" p u l s e s  near the f i r i n g  t h a t r e s u l t when a p u l s e o f  l e v e l i s a p p l i e d to the f i r s t  T r a n s i s t o r s i n t h e "on" c o n d i t i o n were p l a c e d the  Schmitt*  i n series with  charge t r a n s f e r t r a n s i s t o r s t o reduce the e f f e c t s o f  voltage The  f e e d b a c k due t o a f i n i t e  reverse  a d d i t i o n o f the second t r a n s i s t o r  impedance r a t i o  and t h u s  impedance  ratio.  increases the reverse  r e d u c e s any v o l t a g e  feedback  effects* A  change i n t h e c h a r g e t r a n s f e r g a t i n g a r r a n g e m e n t s was made  t o improve  t h e shape o f t h e r e c i r c u l a t e d p u l s e s .  change r e q u i r e d a n a d d i t i o n a l g a t i n g p u l s e The A-3.4  final  circuits  are i l l u s t r a t e d  This  generator  i n F i g u r e s A-3.1  and some t i m i n g waveforms a r e g i v e n i n F i g u r e  Details  of the c i r c u i t  (GP2d). to  A-3.5.  o p e r a t i o n a r e g i v e n i n R e f e r e n c e 10  I and  apply  additional  to the f i n a l  circuit  as g i v e n h e r e e x c e p t  f o r the  o p e r a t i o n a l d e t a i l s b r o u g h t about b y t h e above  modifications.  -OO  0  Hrts-n=R  1  (b) P«d  CLOCK.  0-/2£  O&Pid  (e) G-Pld  DECAY MOMO^TI«I6L£ Resistors* Figure  J v , 10%  A-O.-l  (a) (e)  Capacitors* Master Clock GPld  75v, 1 0 % (b)  T r a n s i s t o r s * 2N1309  Frequency D i v i d e r  (c)  GP1  Diodes* (d)  0+2*  1N497  Delay Monostable  ON ON  CLACK, O—f f loop  2-  O © © +2£  3 o CO Resistors*  fv,.  F i g u r e A-3.2  10%  Capacitors*  Pulse Generators*  G.P3  75v, 1 0 %  ( a ) GP2;  o  T r a n s i s t o r s * 2N1309  (b) GP2d;  ( c ) GP3  Diodes*  1N497  ON  -1  r-oC  O D E OUT  -0-I2* loo  MOO  IK  :ioo  18 K  Geo  •8c© To OoJCue. EMITTER  6  >3** >47o  33K  - 4 *  -Oo **CHMITT TRtcSGfertZ  Resistors!  fw,  Figure A - 3 . 3  10%  C a p a c i t o r s ! T5v, 10%  Input A m p l i f i e r , Diode Doubler A m p l i f i e r  Diodes!  1N497,  Gate 1 , S c h m i t t  1N34  ^UfiTfcACTOft.  DooGufcft  Transistors! 2N1309 unless otherwise noted  T r i g g e r s , S u b t r a c t o r and V o l t a g e o> 00  i/OL-T^ce  CHfl«G6.  Resistors?  F i g u r e A-3.4  iw, 10$  TrtfliUif-6.K  Cir«.cCiTS  C a p a c i t o r s : '."•, 10$  Double E m i t t e r F o l l o w e r F o l l o w e r , D i o d e Gate 2  D f i O f i u E . 6 M | T T £ f ? . Po«-l.oW6*>  T r a n s i s t o r s * 2N1309, 2N1381  G a t e , Charge T r a n s f e r C i r c u i t s ,  DlOOE  Diodes*  Double  ( i ^ T C Z.  1N497  Emitter  70  CLOCK  TAP |  TAP 3  GPl +  GPId —  £  GP2 + —  4  GP2d +  GP3+•^6  F i g u r e A-3,5  Coder T i m i n g  Waveforms  71 REFERENCES  1.  O l i v e r , B.M., P i e r c e , J.R., and Shannon, C.E., "The P h i l o s o p h y o f PCM", P I R E . V o l . 36, No. 11, p . 1324, November 1948.  2.  G o o d a l l , W.  3.  Oxford,  4.  B l a c k , H.S.,  5.  A r m s t r o n g , A . J . , " P u l s e Code M o d u l a t o r U s i n g J u n c t i o n Transi' s t o r s " , J I E E , V o l . 106, B, 1959.  6.  S e a r s , R.W.,  7.  Meacham, L.A. and Peterson, E . , "An E x p e r i m e n t a l M u l t i c h a n n e l PCM System o f T o l l Q u a l i t y " , B S T J . V o l . 27, pp. 1-43, J a n u a r y 1948.  8.  Smith,  9.  F e d i d a , S.,  "PCM U s i n g C i r c u l a t i n g P u l s e s " , E l e c t r o n i c E n g i n e e r i n g . V o l . 24, No. 295, pp. 356-61, A u g u s t 1952.  10.  H a f e r , R.A.,  "A Coder f o r PCM U s i n g C i r c u l a t e d M.A.Sc. T h e s i s . UBC, A u g u s t 1959.  11.  Chang, J . , "A T r a n s i s t o r i z e d D e c o d e r f o r P u l s e Code M o d u l a t i o n " , M.A.Sc. T h e s i s . UBC, ( E l e c . Eng.), A u g u s t 1961.  12.  Stiffler,  13.  N y q u i s t , H., " C e r t a i n T o p i c s i n T e l e g r a p h T r a n s m i s s i o n T h e o r y " , A I E E T r a n s a c t i o n s , . V o l . 47, pp. 617-644, April 1928.  14.  Shannon, C.E., "A M a t h e m a t i c a l T h e o r y o f C o m m u n i c a t i o n " , B S T J . V o l . 27, p p . 379-423, J u l y 1948; pp. 623625, O c t o b e r 1948.  M., " T e l e p h o n y b y PCM", Bell J o u r n a l . V o l . 26, J u l y 1947.  System T e c h n i c a l  A . J . , "PCM S y s t e m s " , P I R E . V o l . 41, J u l y 19.53.  B.D.,  pp.  859-865,  E d s o n , J.O., " P u l s e Code M o d u l a t i o n " , T r a n s a c t i o n s , V o l . 66, 1947.  " E l e c t r o n Beam D e f l e c t i o n V o l . 27, p . 44, p . 148.  AIEE  Tube f o r PCM",  " C o d i n g by F e e d b a c k M e t h o d s " , PIRE, V o l . No. 8, p. 1053, A u g u s t 1953.  BSTJ.  41,  Pulses",  J . J . , " S y n c h r o n i z a t i o n o f T e l e m e t r y Codes", IRE T r a n s a c t i o n s on Space E l e c t r o n i c s and T e l e m e t r y . V o l . SET-8, No. 2, June 1962. -  72 15«  Fletcher,  H.* S p e e c h and H e a r i n g i n Communication, V a n N o s t r a n d , 1953, p . 80.  Princeton,  16*  D a v e n p o r t , W.B.* J r . , "An E x p e r i m e n t a l S t u d y o f Speech Wave P r o b a b i l i t y D i s t r i b u t i o n s " * J o u r n a l of the A c o u s t i c a l S o c i e t y o f A m e r i c a , V o l . 24* p p . 390399, J u l y 1952*  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0105036/manifest

Comment

Related Items