Josephson Junctions as Microwave Heterodyne Detectors.
CALIFORNIA UNIV BERKELEY DEPT OF PHYSICS
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The properties of point contact Josephson junctions operated as 36 GHz heterodyne detectors have been extensively studied. The measured performance is in good agreement with the theory developed for microwave coupling, conversion efficiency, and intrinsic noise based on the Resistively Shunted Junction model. A tunable cavity matching structure was designed to obtain good RF coupling to the point contact. By operating vanadium junctions at 1.4 K, a single side band mixer noise temperature of 54 K referred to the input with a conversion gain of 1.35 and a signal bandwidth of the order of 1 GHz is achieved. This is significantly better than existing resistive mixers in this frequency range. Harmonic mixing, mixing in the presence of relaxation oscillation, and self local oscillator mixing with Josephson junctions is also tried, but the results are not as promising as fundamental mixing with an external local oscillator. Finally, two additional topics are discussed a Josephson effect homodyne detector, and a proposed design for superconducting bolometers making use of the recently developed superconducting quantum interference devices. Author
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