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Measurement of the propagation characteristics of shielded and unshielded dielectric-tube waveguides Makino, Ikufumi

Abstract

Accurate measurements of the propagation coefficient of the HE₁₁ mode on polythene-tube waveguides in air and surrounded by a polyfoam shield are reported. These were carried out at X-band frequencies using a cavity-resonance method. The results obtained confirm previous theoretical predictions although there is an element of uncertainty concerning the exact dielectric properties of the commercial grade polythene tubes used. The measurements also yielded the phase coefficient of the HE₁₁ mode which was confirmed by measurement of the radial decay of the electric field outside the tube. Enclosing the dielectric-tube in a low-density, low-loss polyfoam shield resulted in only a slight degradation of the attenuation characteristics of the waveguides. Measurements of the phase characteristics of the higher order TE₀₁ and TM₀₁ modes on the tube at frequencies close to cutoff are also reported.

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