600-GHz superconducting receiver integrated circuit comprising log-periodic antenna SIS mixer and SQUID array local oscillator

摘要

Abstract: An integrated quasioptical receiver circuit comprising planar complementary log-periodic antenna, SIS mixer with microstrip matching transformers and parallel array of unshunted SIS junctions operating as a local oscillator has been designed, fabricated and tested. The array of parallel SIS junctions united in a microstrip transmission line can be described as a Josephson transmission line (JTL) with single flux quanta synchronously moving along the array of quantum interferometers. The JTL with 20 junctions each 4 $mu@m in diameter has critical current 4.5 mA, normal resistance 0.3 approximately ega and a self-detection step at about 1.1 mV. The step width is over 1.5 mA in current scale and 50 $mu@V in voltage scale that corresponds to about 1 $mu@W oscillation power and 25 GHz tuning range with 550 GHz central frequency. A current applied along the top electrode of the JTL allows to vary the output power of such oscillator. The advantages of such oscillator in comparison with Flux-FLow Oscillator are higher impedance of microstrip line about 10 approximately ega that makes easier matching to SIS mixer, lower losses at frequencies about the energy gap for Nb, narrow linewidth and the possibility to tune output power. THe SIS junction IV curve shows current steps at about 1.2 mV that corresponds to the matching circuit central frequency about 600 GHz that is close to JTL central frequency. !13