Compact microstrip dual-band filter with stepped-impedance resonators

Abstract

A microstrip dual-band filter using a stepped-impedance resonator is proposed. The designed filter is centred at 1.68/2.99GHz. It can provide two passbands, one in the L-band and one in the S-band. The relative bandwidth of both bands were 3.27 and 2.85%. The size of the proposed filter is 52.2mm in width and 40mm in length. The filter achieved insertion loss of less than 1dB and return loss of greater than 20dB in each band. The isolation between these two passbands is better than 25dB from 1.96 to 2.59 GHz. The filter is analysed and designed by Sonnet software. It is shown that the theoretical analysis and simulated performances are in good agreement.