Waveguide dielectric millimeter band filter with enhanced selectivity

The structural design of a waveguide dielectric filter which can be used at the input to a low noise mixer and meet the requirements placed on the selectivity, while assuring low losses within the passband was analyzed. The case of the H sub 01 mode incident on a layered dielectric structure in a rectangular waveguide is considered. Expressions are derived for the transmission gain and reflection factor, and the input impedance of the system of coupled dielectric resonators. Curves are plotted from theoretical and experimental data to show the voltage standing wave ratio and attenuation as a function of frequency for such filters which consist of seven quartz, polikor or ceramic resonators. These waveguide dielectric filters are composed of a set of hollow waveguide sections in which the dielectric resonators metallized on the end faces are press fitted in a definite sequence. A variation in the dielectric permittivity and length of the coupled waveguide sections of 3 to 4%, or even the thickness of the dielectric resonators by 0.5% has no significant impact on the filter response.