W-band low-loss bandpass filter using rectangular resonant cavities

This study shows a high performance of W-band bandpass filter using a simple structure, which has advantages of low cost and simple process. This filter is composed of four rectangular resonant cavities, which are connected together by series. We designed and optimised the sizes of four cavities and the sizes of coupling holes by Ansoft´s High Frequency Structure Simulator 13.0 (HFSS 13.0). The simulation result of the filter shows that it has the centre frequency at 92.62 GHz, 4.07% (3.86 GHz) bandwidth, a 0.4 dB insertion loss in the passband and a 1.51 rectangular coefficient. The measured response of the filter agrees with the simulation result, which has the centre frequency at 92.6 GHz, 4.53% (4.20 GHz) bandwidth, and an average insertion loss less than 0.5 dB in the passband. The rectangular coefficient of test result is 1.61. The simulation result also prove that it is easy to obtain a W-band bandpass filter which has a centre frequency range from 90 to 100 GHz with a bandwidth ranging from 3 to 9 GHz by slightly adjusting key sizes of the structure, such as chamfer radius and thickness of the iris.