Bandpass filtering power divider with sharp roll-off skirt and enhanced in-band isolation

Abstract

This paper presents a compact device with functions of frequency selecting and power dividing simultaneously. Open-stub loaded dual-mode resonators are selected as the basic building blocks. By cascading two dual-mode resonators, a novel fourth-order inter-cross-coupled coupling scheme containing mixed coupling is realized and employed to replace the λ/4-line sections of conventional Wilkinson power divider (PD) to improve out-of-band rejection performance. Two surface mounted resistors of different values are placed between channels to obtain high in-band isolation between output ports. Furthermore, a filtering PD operating at 4.45 GHz is designed, fabricated and tested to demonstrate the efficacy of the proposed design. Four finite transmission zeros positioned at 3.85 GHz, 4.25 GHz, 4.75 GHz and 5.4 GHz respectively are achieved which will result in good frequency selectivity. Very good agreement is observed between the simulated and experimental results with approximately 1.3 dB insertion loss and over 18 dB isolation over the entire passband.