Compact Cross-Coupled Bandpass Filter with Wide Stopband and Low Radiation Loss Using SIDGS

In this paper, a compact cross-coupled bandpass filter (BPF) with wide stopband and low radiation loss is proposed based on the substrate integrated defected ground structure (SIDGS). The SIDGS resonator can miniaturize the circuit size, reduce the radiation loss, and suppress the harmonics, simultaneously. To achieve the filtering response with wide stopband, three coupled SIDGS resonators with discrepant harmonic positions are used. Besides, an additional weak coupling path is introduced to generate a transmission zero at upper stopband. To verify the mechanism, a compact three-order BPF operating at 2.62 GHz (i.e., f(0)) is implemented and fabricated. Measured stopband bandwidth is up to 26 GHz (i.e., 9.92f(0)) with a rejection level higher than 27 dB.