Resonant Cherenkov radiation in Josephson flux flow oscillators with integrated meander-shaped transmission line

A novel Cherenkov flux flow oscillator (CFFO) is considered. The system con sists of a long Josephson junction with an overlaying meander-shaped stripl ine, The traveling wave in the line is exited at each intersection point by the chain of fluxons moving along the junction. At certain resonance frequ encies the radiation delivered to the stripline from all intersections poin ts interfere constructively and the generated power reaches its maximum val ue. To first order the resonance condition is given by the distance between the fluxons, and is independent of the system boundaries. So one can chang e the resonance frequency by varying the external magnetic field. This is r adically different from oscillators relying on conventional internal juncti on resonances such as the Fiske resonance, and allows for design of a power ful CFFO which can be electronically tuned. The existence of resonant inter actions with both forward and backward waves is shown, and the analogy to t he Cherenkov synchronism is demonstrated. Numerical simulations confirm the analytical predictions and allow us to investigate the strongly nonlinear case. The proposed CFFO is ideally suited for realization in HTSC technolog y.