Design of microstrip wideband bandpass filter using U shaped defected ground structure

This paper proposes a microstrip wideband bandpass filter using `U' shaped defected ground structure (DGS). It consists of four coupled U shaped slots etched on the ground plane and is fed by parallel coupled `T' shaped microstrip feed lines on the top. The gap between T shaped feed lines act as an inverter which will convert bandstop response to bandpass response. Due to the arrangement of etched slots and due to cross coupling between these slots, the Alter exhibits two transmission zeros on either side of the passband, thereby improving selectivity of the filter on both sides of the passband. Prototype filter simulated shows an insertion loss of 1.15 dB with fractional bandwidth (FBW) of 29.73% centered at 5.75 GHz. The designed filter has the benefits of low insertion loss, high selectivity, low cost and is easy to fabricate, which can be used for modern wireless communication systems.