Abstract
The limitations of filter synthesis methods based on classic equivalent circuits with the enhanced distributed models and synthesis procedures able to overcome such limitations are presented. A modified procedure that corrects the waveguide lengths has been proposed. The input and output reflection coefficients of the ideal prototype steps are real. The shunt capacitive effect introduces a phase shift in the reflection coefficients of each waveguide step. The representation of the filter structure can be improved if the waveguide steps are analyzed with a full-wave electromagnetic (EM) simulator, and their responses are stored in the form of ABCD matrices. The desired filter passband cutoff frequency was 11 GHz, with a specified return loss of 25 dB, and a gap height greater than 4.25 mm. High-power applications with wide stopbands often require impractical waveguide sections. The accurate EM simulators are used to find an almost exact equivalence between the prototype and the filter parts.
