A simple design for waveguide cavity filters with improved stopband performance

This paper proposes a new configuration for designing bandpass filters (BPF) using multimode rectangular cavity resonators. Unlike conventional BPF designs, the multiple modes are not degenerate but occur at different frequencies. A bandpass filter has been designed by coupling one such mode using a resonant slot. The uncoupled modes contribute transmission zeros (TZ) thus improving rolloff and stopband performances. A simple simulation based design procedure has been proposed for the design and simulation results are given. Equivalent lumped element circuit representations has also been given which validates both theory of operation and given design procedure.