Superconducting Submm Integrated Receiver with Phase-Locked Flux-Flow Oscillator for TELIS

We present results of a single-chip superconducting integrated receiver development for the Terahertz Limb Sounder (TELIS) balloon project. TELIS is a collaborative European project to build a three-channel heterodyne balloon-based spectrometer for measuring a variety of the stratosphere constituents. The Superconducting Integrated Receiver (SIR) comprises in one chip a planar antenna integrated with a superconductor-insulator-superconductor (SIS) mixer, a superconducting Flux Flow Oscillator (FFO) acting as Local Oscillator (LO) and a second SIS harmonic mixer (HM) for FFO phase locking. An improved design of the FFO for TELIS has been developed and optimized. A free-running linewidth between 9 and 2 MHz has been measured in the frequency range 500 - 710 GHz. As a result the spectral ratio of the phased-locked FFO varies from 35 to 90 % correspondingly, ensuring that at least half of the phase-locked FFO power in the primary frequency range for TELIS (550-650 GHz). The FFO performance required for successful TELIS operation is discussed. New generation of the SIR for TELIS with improved FFO performance has been developed and preliminary tested. It is important to ensure that tuning of a phase-locked (PL) SIR can be performed remotely by telecommand. For this purpose a number of approaches for the PL SIR automatic computer control have been developed. Preliminary measurements give an uncorrected double side band (DSB) noise temperature of about 200 K measured at 2.1 K with the FFO phase-locked at 660 GHz. The effect of FFO linewidth imperfections on retrieval procedure is discussed.