Compact balanced bandpass filter based on dual‐sided parallel‐strip line

Abstract

A novel compact balanced bandpass filter with wideband common mode rejection is proposed in this article. The intrinsic out‐of‐phase characteristic is realized by the 180° swap structure, which is based on dual‐sided parallel‐strip line, wideband common mode (CM) rejection can be easily achieved with compact size and simple configuration. Modified coupled line resonator (MCLR) is applied to implement passband response, and MCLR is composed by conventional coupled line terminated with a λ/4 open stub. To validate the performance, one prototype with 20% 3 dB fractional bandwidth center at 2.2 GHz is designed and fabricated, over than 18 dB CM rejection extended to 2.94f₀ can be realized, good agreement can be obtained.