Reflection quasi-optical circulator at millimeter-wave G-band

In order to meet the requirement for millimeter-wave measurement system and solve the problem of the high frequency band test, the reflection quasi-optical circulator operating at G-band (140-220GHz) is studied. As the reflective type can easily adjust the bias magnetic field, the accuracy requirement for parameters such as ferrite thickness, etc. is reduced. Thus the multi-layer medium model can be optimized in the design. A quasi-optical test bench and a test method are established for the experiment, and dielectric properties are also presented. Results on 170-195GHz show that the G-band circulator has an isolation higher than 20dB and an insert loss less than 3.6dB over a relative 8% bandwidth. Studies show that the reflection circulator is suitable for high frequency application due to its relaxed tolerances of design parameters.