Isolators Designed for Low-Insertion Loss

Advanced MMW Ferrite Components Isolators Designed for Low-Insertion Loss Commercial Faraday rotation isolators have been around since the 1970’s. Traditional builds have good isolation throughout the microwave and millimeter-wave bands (typically > 20 dB and in many cases > 30 dB across the band). The insertion loss is relatively low in the microwave bands but steadily increases with frequency. At mm-wave frequencies the insertion loss becomes problematic. 

For example, in the WR-10 band (75-110 GHz) the insertion loss can exceed 3 dB, precluding their use in many systems. In the WR-3.4 band (220-325 GHz) the insertion loss can be more than 7 dB. There are very few manufacturers in the bands above 50 GHz. Isolators in the WR-4.3 and WR-3.4 bands were manufactured many years ago but are now difficult to find. At these high frequencies, the constituent parts are very small, and difficult to fabricate and align. And with > 7 dB insertion loss, there isn’t much demand. At these frequencies, system designers cannot tolerate that much signal loss.