Study of Millimeter Wave Circulators based on the methods of circular polarization isolation

The millimeter wave circulators based on the methods of circular polarization isolation were studied and modularized in this paper. The modular circulators with polarization converter and orthomode transducer are designed and simulated at 77 GHz and 224 GHz. The polarization converters are realized by multilayer metamaterial and grooved circular waveguide respectively. The orthomode transducer is realized by the metal wire grid and microstrip probe structure, whose cross-polarization isolation could reach 60-dB. Finally, the modular circulator has about 0.5-dB total loss and 46-dB isolation at 224 GHz.