Finite element analysis of a high power broadband circulator for air traffic surveillance radar

Current radar applications require the design of high power circulators with increased bandwidth and reduced insertion loss. A technique called “mode segregation” is used to select a bias field region above ferrimagnetic resonance, which avoids high power nonlinear loss to achieve high power/bandwidth and temperature stability. A finite element magnetostatic/ microwave procedure is used to implement this technique for the differential phase shift section of a 4 port circulator to be used in ground surveillance. This study dictates that the circulator has an operating bandwidth from 9.6–10.4 GHz, handles peak power of 0.60 MW, and 1.8 KW average power above ferrimagnetic resonance. Minimum 20 dB isolation with an insertion loss less than 0.2dB over the operating frequency band was achieved. Calculations agree well with the experimental data.