HTSC Josephson oscillator with inhomogeneous bias

Properties of long Josephson junctions, fabricated from YBCO high-temperature superconducting thin films, are investigated experimentally and by numerical modeling. Since the junctions are placed into broadband log-periodic antennas, it poses limitations on junction’s bias feed properties, affecting their dynamics. It is shown that biasing junction at the output end, connected to the antenna, makes current–voltage characteristics more steep in comparison with biasing along the whole length and at the input end. The radiation properties of Josephson junctions are studied by receiving signals using dipole antenna array with cold electron bolometers. Broadband frequency tuning of the oscillator with radiation up to 800 GHz, being restricted by the receiver antenna range, is demonstrated. It is shown that for the considered junction lengths and bias feed types, the maximal radiation power varies weakly, leading to a high bolometric response.