Computer Aided Design of Dielectric Resonators Filters in Circular Waveguide

The paper describes a new CAD procedure for designing bandpass filters realized with ring or cylindrical dielectric resonators (DRs) placed in circular waveguide below cutoff and operating on the first TE or TM or Hybrid resonance. The procedure employs an equivalent circuit of the filter structure in order to allow a synthesis approach to the design; the results obtained are however very satisfactory even for moderate bandwidth filters. The characterization of DR inside the circular waveguide is performed by means of mode matching techniques, which allow a very accurate evaluation of the equivalent circuit parameters. Experimental measurements performed on a prototype TM filter designed with the proposed procedure have shown substantial agreement with the expected performances.