Microwave integrated circulators

This paper presents results of several integrated circulators built in microstrip transmission line. The circulators are of the symmetric junction variety and utilize polycrystalline magnesium-manganese ferrites. Three-port circulators and four-port circulators have been built in x-band. The four-port structure is essentially two three-port circulators fabricated end-to-end on a common substrate. Some of the circulators are fabricated by depositing the metallic microstrip circuit directly onto a ferrite substrate. Some are fabricated by pressing ferrite pucks into an alumina substrate on which the microstrip circuitry is deposited. Small permanent magnets are generally used for bias.