A 3‐port ferrite resonator circuit using slot line

This paper proposes a magnetically tuned 3-port circuit having simultaneously a resonant characteristic and a nonrecriprocal property. In this circuit, a ferrite resonator is placed on the metal conductor side of a slot line on a dielectric substrate and an additional port is created that couples with the resonator. The S matrix of the circuit is derived. The relation between the electromagnetic field and the external Q of the resonator is found and the electromagnetic field distribution of the slot line is calculated. From the calculated results, it is found that there exists an optimum location for the ferrite loading and that the present circuit can be used in a broadband operation. The frequency characteristic and the nonreciprocity are experimentally confirmed. The present circuit has a simple configuration and can be used for a magnetically tuned oscillator that does not require an isolator to eliminate the effect due to load variation.