Wideband Circulators for Use at Frequencies Above 100 GHz to Beyond 350 GHz

High-performance circulators operating at frequencies in the range from 100 to 350 GHz have been developed for application in major measurement systems. These circulators have open quasi-optical structures. The magnetized plates in these devices are of nonmetallic magnetic materials which have both well-developed millimeter-wave gyrotropic properties and the magnetostatic properties of an excellent permanent magnet material. Very few commercially available magnetic materials have been found that meet both the magnetostatic and the magnetooptical selection criteria. Those few have, however, made possible the design, manufacture, and successful operation of high-performance circulators/isolators at these high operating frequencies. Several circulators/isolators of this type have been installed in major measurement systems.