The Operation of Nonreciprocal Microwave Faraday Rotation Devices and Circulators

Abstract

The Faraday rotation effect describes the rotation of the plane of polarization of a linearly polarized wave in an infinite gyromagnetic medium or circular waveguide. This chapter includes a definition of the gyrator network and the description of some common ferrite devices in round waveguides based on Faraday rotation effect, such as Faraday rotation isolators, circulators, nonreciprocal phase‐shifters, and amplitude modulators and switches. Three and four‐port circulators based on turnstile junctions are also described. The simplest component that illustrates the nonreciprocal property of a Faraday rotator is the gyrator circuit. One application of the gyrator network is in the construction of the four‐port differential phase‐shift circulator. An important application of a Faraday section is in connection with the realization of a four‐port Faraday rotation circulator. The geometry of a practical Faraday rotation section usually consists of a ferrite rod inside a circular waveguide filled by a suitable dielectric material.