Quasi-elliptic bandpass filtering power divider with ultra-wide stopband

Abstract

In this Letter, a novel filtering power divider with second-order quasi-elliptic bandpass response is proposed, which has two transmission zeros near to the passband for sharp frequency selectivity. In addition, it is featured by ultra-wide stopband owing to specific topology. For demonstration, a filtering power divider example operating at 3.1 GHz is designed, fabricated and measured. Its 3 dB fractional bandwidth is about 11.9%, and the in-band isolation between two output ports exceeds 20 dB. Specifically, more than 21 dB out-of-band suppression is achieved from the upper side of the passband to 4.8f0, and more than 12 dB suppression is achieved to at least 20f0. The measurement agrees well with the simulation.