Design of Compact UWB Filter Using Parallel-coupled Line and Circular Open-circuited Stubs

Abstract

This article encompasses the design of compact ultra-wideband (UWB) bandpass filter with low insertion loss and high selectivity using circular open-circuited stubs (COSs). Low insertion loss from two COSs and Multiple Mode Resonator (MMR) from three pairs of parallel-coupled lines are constituted to obtain the UWB band. The proposed filter has multiple resonant frequencies in the passband and two transmission zeros perceived at stop band/passband transition edges. It has a 3-dB fractional bandwidth of 110% and it covers the entire UWB band of 3.1–10.6 GHz. The measured passband insertion loss and group delay are 0.35 dB and 0.42 ns, respectively. Moreover, the presented filter is a single-layered structure since it is more comfortable to be integrated into a printed circuit board (PCB). The simulated and measured performance of the presented filter is in good agreement. The filter finds its application in low power handling single-layered PCBs, unlicensed short and medium distance communications.