LAUSR

This letter proposes a novel twin-coaxial resonator (TCR) for the first time, and its application to a balanced bandpass filter (BPF) with compact size and high common-mode suppression. The proposed TCR is composed of two coupled conductive posts within a single cavity, whose fundamental mode is used to construct the differential passband. To illustrate the proposed concept, a second-order balanced BPF is designed, fabricated and measured. The balanced filter owns an insertion loss of 0.45dB with a fractional bandwidth of 3.4% at 1.17GHz. And the common-mode suppression is more than 65 dB in the differential-mode passband. Good correspondence is observed between the measured results and the full-wave simulation results.