Compact dual-band bandpass filter using concentric stepped impedance resonator

Abstract

A dual band bandpass filter for WLAN and WiMAX application is presented in this paper. The proposed filter is realized using concentric U shaped stepped impedance resonator and inward folded open stub resonator. The center frequencies of the pass band are 2.45 GHz and 3.5 GHz. The insertion loss is about 2 dB and 1.5 dB at first and second passband respectively. Two transmission zeros are introduced to improve the selectivity of the filter one is in between two pass band at 2.9 GHz and another is sight of the second passband at 4.4 GHz. The overall dimension of the filter is 14.9 mm by 18.9 mm.