Josephson Self-Coupling & Radiation Linewidth of Flux Flow Oscillators

The two primary objectives of the experimental work presented in this book are the investigations of the Josephson self-coupling effect, and the radiation linewidth of a long Josephson junction used as a flux flow oscillator. The junctions are Nb-AlOx-Nb tunnel junctions implemented on 4:5 x 3 mm2 samples fabricated at the Institute of Radio Engineering and Electronics (IREE) in Moscow, with an approximate normalized length of l = 60. The experimental evidence produced supports the observations by Koshelets et al. [1] that these long junctions exhibit the Josephson self-coupling effect as predicted by Werthamer [2]. As for the investigation of the linewidth, the data do not show the expected proportionality to RD^2, where RD is the differential resistance of the dc I-V curve. The relation looks much more like a proportionality to RD, which is explained by a presence of low-frequency noise in the bias and/or control line current.