Superconducting chip receivers for imaging application

Abstract

Experimental details of the study on a unique superconducting imaging array receiver are discussed. Each pixel contains an internally pumped receiving chip of size 4 mm x 4 mm x 0.5 mm which is mounted on the back of the elliptical microwave lens made from silicon. Each chip comprises a quasi-optical SIS mixer and LO based on a superconducting flux-flow oscillator, all fabricated from the same niobium trilayer, Nb/AlOx/Nb. A new design of the receiving chip has been developed to fit the silicon optics. Properties of the integrated lens antenna were studied using an externally pumped reference SIS mixer which showed antenna sidelobes below -17 dB and a receiver DSB noise temperature, TRX, below 100 K within the frequency range 460 - 500 GHz that is close to the quantum noise. For the imaging array TRX = 150 K has been measured at 500 GHz using internal LO. The concept of the balanced SIS mixer was tested preliminary showing TRX < 100 K within range of 480 - 510 GHz using internal LO. A computer system is routinely used for the Integrated Receiver that includes control of the SIS mixer, frequency tuning of the LO and automatic optimization of the receiver regime for lowest noise temperature.