Isolator using a ferrite-coupled-lines gyrator

The theory and design of an isolator based on a new concept using a section of axially magnetised ferrite coupled line (FCL) are presented. The isolator consists of a resistive four-port junction cascaded with an open- or short-circuited section of FCL representing a gyrator circuit. Design procedures for microstrip and slot-line configurations are described. The main feature of the isolator is its multiple reversing of operating direction with frequency. Application of the microstrip FCL section to the design of a gyrator is considered. The performance of the isolator is predicted by cascading S-matrices of the microstrip FCL gyrator and resistor circuit. The simulated scattering characteristics of the proposed isolator confirmed the correctness of the concept of the proposed novel nonreciprocal device.