High-Performance Wideband Balanced Bandpass Filter Based on Transversal Signal-Interference Techniques

A novel high-performance wideband balanced bandpass filter based on transversal signal-interference techniques is proposed in this article. Two signal-propagation paths consisted of coupled lines structure are used to realize two transmission zeros for the differential mode passband. Folding coupled lines are used to reduce the size of the balanced filter, and the source-load cross-coupling lines can generate additional transmission zeros to suppress the common mode signal. To validate the design, a prototype with center frequency at 2.2 GHz for long-term evolution (LTE)-band with 3-dB fractional bandwidths of 65.4% for the differential mode is designed and fabricated.