Differential magnetless circulator using modulated bandstop filters

Abstract

In this paper, we present a differential magnetless circulator by combining two angular-momentum-biased single-ended circulators, each of which consists of three first-order bandstop LC filters connected in a delta topology and modulated in time with a phase difference of 120 deg between each other. Compared to a single-ended architecture, the differential one drastically reduces even-order intermodulation products, improves insertion loss, extends the bandwidth, and significantly decreases the required modulation frequency. We present the theory of such a circulator and validate it with simulated and measured results.