Wideband Differential-Mode Bandpass Filters With Stopband and Common-Mode Suppression

摘要

This letter presents wideband differential-mode (DM) bandpass filters (BPFs) designed on a microstrip line for ultrawideband (UWB) applications. The proposed design is based on an optimized branch-line structure with extended transmission lines (TLs). An enhanced performance can be obtained using a very simple design approach. The introduced TLs can be used for improving the DM stopband response by introducing multiple transmission zeros (TZs) at the lower and upper stopband. The common-mode rejection level can also achieve around 40 dB within the band of interest. The proposed filters are fabricated for experimental verification. The predicted and measured results show a very good agreement.