HIGH-T-C SUPERCONDUCTING ACTIVE SLOT ANTENNA WITH YBCO STEP-EDGE JOSEPHSON-JUNCTION ARRAY

The high-T-c superconducting active antenna proposed here for millimet er and submillimeter radiowave communications, uses a YBCO slot antenn a with a series Josephson junction array to increase the normal-state resistance of the junctions, in order to ensure impedance matching bet ween the antenna and the junctions. The antenna is a coplanar waveguid e fed slot antenna, which can be easily and monolithically combined wi th the Josephson junctions. The design frequency of the antenna is 10 GHz and the obtained bandwidth of a VSWR less than 2 was 4.1%. Normal- state resistance values of the junction array could be confirmed by me asuring I-V characteristics and 100-MHz impedance measurements, and bo th agree very well. Microwave mixing experiments were carried out usin g the junction array with the antenna, and the experiments showed that the conversion gain of the junction was proportional to the number of the junctions. The conversion gain of an eight-junction mixer with th e antenna was found to be -6 dB.