Angular-Momentum Biased Circulator with a Common-Differential Mode Topology for RF and Modulation Isolation

This paper presents a single ended magnetless circulator with inherent common-differential mode rejection between the RF and modulation paths. The circulator consists of three first-order bandstop LC filters differentially powered and modulated, eliminating the requirement of filters for isolation between the RF and modulation paths. A preliminary printed-circuit-board prototype at 1.78 GHz is fabricated and measured, showing an isolation of more than 20 dB, insertion loss of 5.5 dB, 2.6% bandwidth and power handling of 21 dBm, comparable to other designs in existing literature.