A SIR dual-band microstrip filter loaded with shaped branches

In this paper, a SIR-coupled dual-band bandpass filter is proposed, which has lower insertion loss, better out-of-band rejection. The bandpass characteristics of the dual-band are obtained by bending the SIR and coupling it, and loading the shaped branches. By changing the shape of the shaped branches, a transmission pole is added in the first passband, which reduces the insertion loss of the filter and improves the rejection effect of the stopband. The simulation results show that the dual-frequency bandpass filter has a center frequency of 6.26GHz, an insertion loss of 0.17dB, a return loss of less than -27.8dB, and a relative bandwidth of 15.5% for the low band, and an insertion loss of 0.67dB, a return loss of less than -15.8dB, and a relative bandwidth of 11.6% for the high band, at a center frequency of 9.26GHz.