Oscillation spectral linewidth for some phase-locked Josephson-junction arrays

High effective autoregressive method has been applied to the calculation of the oscillation line width for the promising phase-locked Josephson-junction arrays. It has been found, that the oscillation linewidth decreases with the number N of Josephson junctions proportionally to N for one-dimensional arrays or even more fast for two-dimensional arrays until number N exceeds the coupling radius. It has been shown that in the case of parallel array inserted into superconducting microstrip line, the phase-locked oscillation state in-phase could be provided by the strong interaction between Josephson junctions and electromagnetic standing wave regardless to applied magnetic field. The necessary amplitude of the standing wave is easy attained at McCumber parameter value /spl beta/>1, when the high-frequency Josephson-junction impedance is small in comparison with the strip-line wave impedance. An extra reduction in the linewidth caused by electromagnetic standing wave impact has also been studied. The results are discussed from viewpoint of the possible applications of the structures as submillimeter wave generators.