Designing a Compact Microstrip Dual-Band Filter with Two T-Shaped Resonators and Suitable Frequency Selectivity

Abstract

A miniaturized microstrip dual-band bandpass filter (DBPF) with two T-shaped resonators is proposed. The two T-shaped resonators lead to multiple transmission zeros in the stopband and higher filter selectivity. The filter is analyzed using LC and even/odd mode analyses to determine the transmission zeros. The LC equivalent circuit and transfer function are presented. The proposed filter is symmetrical, so the electrical length and impedance values are used for odd/even mode analysis. The designed DBPF is centered at 1.9/5.54[Formula: see text]GHz and is suitable for WLAN applications. The insertion loss of the filter is less than 0.5[Formula: see text]dB and its return loss is more than [Formula: see text][Formula: see text]dB in each band. Five transmission zeros are created with an attenuation greater than [Formula: see text][Formula: see text]dB. The total area of the proposed filter is [Formula: see text][Formula: see text]mm2. To validate the proper performance of the proposed filter, it is fabricated and measured.