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.