A subharmonic Josephson relaxation oscillator—amplification and locking

The inductance of the shunt loop in a resistively shunted Josephson tunnel junction may cause relaxation oscillations at subharmonics of the Josephson frequency. The relaxation period, the injection locking to a subharmonic of a strong external signal, and the amplification of weak signals were studied in detail. Gains up to 15 dB were achieved, but the noise temperature, which depended upon the harmonic of the relaxation frequency at which the amplification occurred, was high.