On the Design of Broadband Asymmetric Y-Junction Ferrite Circulator for 60-GHz Inter-Satellite Communication

Millimeter-wave (mmW) Y-junction ferrite circulators above 40 GHz have limited bandwidth due to the lack of ferrite materials having a high saturation magnetization above 5000 G and the simple and traditional circuit design approaches that cannot produce wideband circulators in this frequency range. To increase the bandwidth of mmW Y-junction ferrite circulators, novel design techniques for such circulators should be developed to achieve a functional circulator over a wide bandwidth at mmW frequencies. In this article, a Y-junction ferrite circulator is proposed, which is based on the WR15 waveguide standard with broadband performance for 60-GHz inter-satellite communications. An approximate design procedure for the core section of the proposed circulator is presented. The proposed Y-junction ferrite circulator achieves more than 20% bandwidth centered at 60 GHz. In addition, the effect of input power and ambient temperature on the performance of the circulator is studied for an input power of 300 W and ambient temperature in the range from −80°C to 80°C. The experimental prototype is fabricated and measured, where the measured response is in very good agreement with the numerically anticipated counterpart. The fabricated circulator achieves beyond −17 dB matching level with −15 dB isolation and 1-dB insertion loss over the entire bandwidth of interest.