High-Isolation Topology for Filtering Power Dividers Based on Complex Isolation Impedance and Surface Wave Suppression

Abstract

Aiming at high and wideband output isolation, a new topology of filtering power divider based on complex isolation impedance and surface wave mitigation techniques is proposed. Different from previously published filtering power dividers using pure resistor, an analytical design method by using complex impedance is proposed in this article. To formula the complex impedance, the LC equivalent circuit model is introduced, and the closed-form derivation is given accordingly. Based on the calculated impedance, high isolation can be theoretically realized in circuit level. However, the output isolation is limited below 20 dB in practical EM simulations. To solve this issue, the filtering power divider is further investigated in field level. To reduce the crosstalk between adjacent filtering channels, the surface wave mitigation techniques are investigated. Accordingly, a 16-dB enhancement of output isolation is realized, without sacrificing other filtering specifications. For experimental verification, a filtering power divider is designed, fabricated, and measured. A significant size reduction and 36-dB output isolation with over 500% isolation bandwidth can be observed, verifying the validity of the proposed design method.