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

Theoretical and experimental studies have been made of the effects of junction geometry on the performance of the flux-flow type Josephson oscillator. It is shown theoretically that the height and the slope of the current steps appearing in dc I-V curves of the junction, which determine the available power and the radiation linewidth of the oscillator, respectively, are dependent strongly upon self fields in the junction. In order to study the effects of junction geometries on the self fields, computer simulation and experiments have been carries out for an in-line junction, an overlap junction and an overlap junction with a small projection on one side. The best performance is obtained for the overlap junction with a moderate projection on side as expected theoretically.