Development of the Flux-Flow Oscillators for Submm Integrated Receiver

A comprehensive experimental study of the Flux Flow Oscillator (FFO) linewidth on its parameters has been carried out in order to obtain free-running FFO linewidth well below 10 MHz and ensure phase-locked operation of a Superconducting Integrated Receiver (SIR). Essential dependence of the FFO linewidth on its width and idle region dimension has been found. A free-running linewidth between 10 and 2 MHz has been achieved in the frequency range 500 – 700 GHz. As a result the spectral ratio of the phased-locked FFO varies from 30 to 90 % correspondingly. First measurements of the free-running FFO linewidth for the FFOs of different length and comparison of the obtained results with existing theoretical models demonstrate significant dependence of the fitting parameter on the FFO length.