W-band Microstrip Bandpass Filters for Image Rejection

This paper presents three W-band compact mi- crostrip bandpass filters, one of which is realized on ULTRALAM 3850 and the other two on RT/duroid 5880 substrate. They are centered at 94 GHz, with a relative bandwidth of 7.76%, 11.7% and 9.57%, respectively. Each filter has two transmission zeros, and they can be used for image rejection at different frequencies. The filter on ULTRALAM 3850 substrate has an insertion loss of 7 dB at 94 GHz and a suppression of 34 dB at 83 GHz. The two filters on RT/duroid 5880 substrate have an insertion loss as low as 2.5 dB and 1.6 dB at 94 GHz, and a suppression of 17 dB at 80GHz and of 46 dB at 73 GHz, respectively. The paper also presents a combination of a filter on RT/duroid 5880 substrate and SiGe TL ICs. It shows a loss of 5.9 dB at 94 GHz and suppression of around or better than 30 dB at the frequency from 79 GHz to 81 GHz.