Design of New Miniaturized Broadband Bandpass Filter Based on SIR

In this paper, a compact and miniaturized wideband bandpass filter based on resonant ring loading stepped impedance resonator is designed. The filter designed in this paper uses the resonant ring as the basic resonator unit. By loading the SIR, the passband width of the filter is improved. The 3 dB bandwidth of this filter is 300 MHz, and the relative fractional bandwidth is 15%. Etching a complementary open resonant ring defected ground structure (DGS) on the floor that changes the current distribution on the floor and creates a band gap with passband characteristics, making the filter compact and compact. The size of filter is 3.5 cm * 4.0 cm. The simulation results show that the filter center frequency is 2.0 GHz, the return loss is 29 dB, and the insertion loss is 1.1 dB. The filter introduces two transmission zero points of 1.3 GHz and 2.6 GHz on both sides of the passband, which improves the out-of-band rejection of the filter. The filter structure designed in this paper has the advantages of small size, wide bandwidth and strong stop band rejection, which verifies the feasibility of the filter design.