Design of Wide Stopband for Waveguide Low-Pass Filter Based on Circuit and Field Combined Analysis

Abstract

In this letter, a combined approach based on circuit equivalent and field analysis is employed to design a waveguide low-pass filter. According to the field analysis and out-of-band transmission poles responses, the transmission pole spacing distribution method is proposed to obtain a wide stopband. The simulation indicates that this method can provide a well-performed harmonic suppression. Different from the large-scale parameter optimization method for the wide stopband, this technique has the advantage of consuming relatively small computation resources. Finally, the X-band waveguide low-pass filter is fabricated and tested. Measurements show that the stopband suppression can exceed the fourth-order harmonic of the fundamental mode with more than 56-dB suppression levels.