| Summary: | We propose a low loss and high selectivity bandpass filter with defected structure on GaN-on-Silicon. GaN-on-Si exhibits a high insertion loss due to the presence of parasitic channels at the AlN/Si interface. It is necessary to strengthen the coupling between the resonators to achieve a low loss. However, this results in weaker suppression of adjacent channels and lower selectivity of frequencies. The designed filter consists of square spiral defect structure resonators and a step impedance resonator, which provides tunable transmission zero and facilitates the adjustment of pass band. With an interdigitated capacitor, at a frequency span from 3.3 to 4.9 GHz, the proposed filter has a low insertion loss of 2.71dB and improves the suppression of adjacent channel (5.8 GHz) by 11.2 dB compared to the traditional SIR filter. The out-of-band suppression of the filter is better than 15.93 dB at 20 GHz. Compared to the traditional SIR filter, the proposed filter achieves a steep transition zone, and an out-of-band rejection reduction by at least 6.6 dB.
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