Dual‐mode dual‐band bandpass filter design utilising cylindrical TM‐mode cavities
This letter presents the design of a novel dual-mode dual-band bandpass filter that utilises the TM210 and TM020 modes of cylindrical cavity resonators for millimetre-wave operation when fed with standard WR-10 waveguide ports. In this manner, the two selected modes of the cylindrical cavity resonators are demonstrated as a single propagation path for fixed dual-passband responses without the need of cavity perturbations or tuning screws. The passbands are designated for centre frequencies at approximately 102.8 and 110.9 GHz and exhibit a four-pole Chebyshev characteristic in each of the passbands, which are separated by a transmission zero location. Simulated and measured results of the prototype are presented to verify the design.