Compact Pentagon Ultra-Wideband Bandpass Filter with Good Out-of-Band Performance

Abstract

A novel compact pentagon ultra-wideband band-pass filter with spurious suppression over a very wide band is proposed. The filter is based on a circuit model using hybrid bended pentagon microstrip and five quarter-wavelength short-circuited stubs, and using double reverse U-shaped defected ground structure (DRU-DGS) provides attenuation pole to suppress the second spurious harmonic. The design was successfully realized in theory and verified by full-wave EM simulation of the full layout and the experiment. The proposed filter had a good performance, including an ultra-wideband bandpass (3.1–10.6 GHz), low insertion loss, sharp rejection, and a flat group delay of about 0.10 ns over the most center band. The filter also demonstrated an UWB reject band from 12 GHz to more than 20 GHz at –20 dB.