Microwave radiation and sensing of Josephson junction with the log-periodic toothed trapezoid antenna of high T-c superconducting films

Using high temperature superconducting thin films, we designed and fabricat ed Josephson junctions associated with a log-periodic toothed trapezoid ant enna. Microwave self-radiation from the Josephson junction was measured by using both a superheterodyne receiver at the center frequency of 22 GHz and an external waveguide system. In the case of junction incorporated with an antenna structure, there was a significant increase of power by an order o f magnitude with respect to a junction without antenna. Under the 22 GHz ir radiation, we observed distinctive Shapiro steps in the I-V measurement, wh ich allowed as estimating the received power of the junction. The received power of the junction with an antenna exhibited as a large increase as that of a self-radiation. Our results indicate that a Josephson junction with a n antenna is very effective for the microwave coupling between Josephson ju nction and free space. The combined device can be used either for a high po wer microwave source or for a high sensitive sensor.