The Turnstile Junction Circulator

Abstract

This chapter describes the turnstile geometry of the original waveguide junction circulator. The transition between the circular gyromagnetic waveguide and a typical rectangular waveguide feed may be catered for by introducing ideal transformers at the terminals of counterrotating eigen‐networks. A classic nonreciprocal ferrite device, which relies on a Faraday rotation bit, is the four‐port turnstile circulator. The H ‐plane three‐port turnstile junction circulator consists of a circular guide containing a longitudinally magnetized ferrite section at the junction of three rectangular waveguides. The design of any junction circulator is incomplete without a formulation of its scattering matrix. Equivalent waveguide models are often employed to represent inhomogeneous waveguides or transmission lines. The cavity resonator in the design of a junction circulator is a half‐wave long geometry with open flat faces separated by dielectric spacers from top and bottom pistons. The dielectric gap in the design of a three‐port junction circulator fixes the so‐called in‐phase mode of the junction.