WAVE-GUIDE PERMITTIVITY MEASUREMENT USING VARIABLE-LENGTH SAMPLES ANDAN UNCALIBRATED REFLECTOMETER

A method is presented to measure the complex permittivity of samples i nserted into waveguides. The method is based on reflection coefficient measurements for four different sample lengths, which are used to det ermine the complex propagation constant of the guide's fundamental mod e. For simple waveguide geometries, the complex permittivity can be ca lculated, assuming a value of 1 for the relative permeability. Unlike classical waveguide techniques, this method does not require calibrati on of the reflectometer, and it can be used with samples that are narr ower than the waveguide cross section's main dimension, By using narro wer samples, the upper frequency limit of the method can be increased. Measurements in an S-band rectangular waveguide using the proposed me thod are presented and compared with results obtained with a cavity pe rturbation method, Very good agreement has been found over the frequen cy range prescribed for the method, Results are shown for completely f illed and partially filled waveguides.