Effects of junction geometry on performance of flux-flow type Josephson oscillator

The effects of junction geometry on the performance of the flux-flow type Josephson oscillator are studied theoretically and experimentally. The output power and the radiation linewidth of the oscillator are determined, respectively, by the height and the slope of the current steps appearing in the dc I-V curves of the junction, which are strongly dependent upon self-fields in the junction. Computer simulation and experiments are carried out for an in-line junction, a conventional overlap junction, and an overlap junction with a projection on one side, in order to study the effects of junction geometries on the electromagnetic field. The best performance is obtained for the overlap junction with a projection on one side, as expected theoretically.