SUPERCONDUCTOR FERRITE PHASE SHIFTERS AND CIRCULATORS

We have previously demonstrated high-T-c superconductor/ferrite nonrec iprocal microwave phase shifters that avoid de magnetic-flux penetrati on of the superconductor through a novel design of the magnetic circui t, and thus operate with very low loss, Recently, a simplified magneti c structure has been introduced, and devices with approximately 0.1 dB insertion loss with 500 degrees of phase shift (figure of merit 5000 deg/dB) at 10 GHz and 77 K using YBCO Rave been demonstrated, The same operating principles have been applied to the design and fabrication of circulators, By combining three low-loss phase shifters and three T junctions on a ferrite substrate in a configuration with three-fold s ymmetry, a three-port switching circulator has been demonstrated using niobium at 4 K, The insertion loss is less than 1 dB, the isolation g reater than 20 dB, and switching time less than 1 ys. The switching ci rculator can serve as a low-loss, high-speed rf switch, Extension of t his design to YBCO will be discussed, Higher performance, reduced weig ht and volume, as well as lower cost are anticipated for microwave sys tems that can benefit from such circulators and phase shifters.