A 400MHz Direct Digital Synthesizer with the AD9912 : Part I : design and fabrication of the device Da Costa, Daniel; Mulholland, Brendan
Part I of this report discusses the design and and fabrication stage of this project. At time of writing, testing is on hold while a complete prototype device has been assembled. Part II will follow and will include documentation the testing procedures, the results and all recommendations. This project aimed to design, build and test a complete and functional Direct Digital Synthesizer (DDS) device with output frequencies of up to 400MHz. A DDS is a device capable of digitally generating sinusoidal waves with programmable frequency and phase. The Analog Devices 9912 (AD9912) was chosen as a suitable DDS Integrated Circuit (IC) and this was used in the project design. An enclosure also had to be built to house the DDS device. The device had to be compatible with an existing parallel control interface used in the lab, requiring a parallel-to-serial converter, as the AD9912 requires a serial interface. This parallel-to-serial converter was designed and prototyped on a breadboard to verify correct operation. It was also necessary for the device to minimize noise. This was accomplished with a passive analog filter circuit that was simulated in SPICE and confirmed to meet design specifications. Complete designs and fabrication files for the circuit and enclosure had to be provided. The schematics for the board were completed and a PCB layout was designed from this schematic. The PCB layout generated all files required for manufacturing. The enclosure was modifed from an existing design to better accommodate the PCB layout and to improve heat dissipation. Twenty PCBs had to be manufactured and parts had to be ordered for 15 boards. These have all arrived and a prototype device is currently being assembled. Enclosures for 15 boards also had to be ordered and these are all currently being manufactured.
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