A small bandstop microstrip filter for UWB applications

Abstract

A small bandstop microstrip filter for ultra-wideband application is proposed. The proposed filter combines the traditional short-circuited stub highpass filter and the open-circuited stub bandstop filter on the mitered 50-Omega microstrip line. The distributed highpass filter scheme is applied to achieve highpass filtering characteristics over ultra-wideband frequency band (3.1-10.6 GHz) and the open-circuited stubs are used to obtain the band rejection function at Wireless Local Area Network frequency band. The measured results show that the proposed filter has a wide passband characteristic of 132.12% (2.16-10.57 GHz), with the return loss of less than - 10 dB and 3-dB stop band of 14.37% (5.17-5.97 GHz). The measured group delay is less than 0.65 its within the passband except the rejection band.