A Novel Circulator Construction With High Multipactor Threshold and High Isolation for Aerospace Applications

In this article, a tapered matching structure in a circulator junction is employed in order to achieve the purpose of high isolation and multipactor suppression in spacecraft electronic equipment. This matching structure consists of multiple ramped metal steps. Compared with the traditional flat steps, it changes the electric field distribution in the circulator junction, thus destroying the resonance condition of the secondary electrons. And it changes the trajectory of the secondary electrons. These particles tend to escape the multipactor sensitive region. So, the purpose of multipactor suppression is reached. Besides, a good match between the circulator junction and the waveguide is obtained by using multiple ramped metal steps. So, high isolation is achieved. Finally, an S-band ferrite waveguide circulator with these characteristics operating at frequencies in the range of 3.4–4.2 GHz is designed, fabricated, and measured. The isolation value of the circulator achieves a maximum value of 43 dB near 4 GHz. And the isolation exceeds 25 dB and the insertion loss is less than 0.3 dB over a bandwidth of 21% centered at 3.8 GHz. In addition, the experimental results show that the multipactor threshold of the circulator reaches 10000 W.