Performance of a compact 557-GHz heterodyne receiver front-end

Abstract

Sub-millimetre wave or terahertz heterodyne receivers operating above 300 GHz are key instruments for many space applications. For example, they are required for monitoring of the earth’s atmosphere or for detection of molecules that are important for the chemistry other planet’s atmospheres, for example water vapour. Meteorological phenomena, which can be studied at these frequencies, are cloud ice water content, ice particle sizes and distribution, which are important parameters for the hydrological cycle of the climate system and the energy budget of the atmosphere. Existing terahertz heterodyne receivers are usually bulky due to complex local oscillator (LO) chains. In a joint effort (project “TeraComp”) [1], we have developed a compact and efficient 557-GHz heterodyne receiver front-end with low power consumption and low noise temperature by minimizing the number of components, through integration, in the LO chain. The front-end consists of a low noise subharmonic Schottky diode membrane mixer, a 275 GHz Heterostructure Barrier Varactor frequency tripler, a 92 GHz mHEMT power amplifiers and a 15 to 92 GHz 6x multiplier as part of the LO chain. The receiver covers the frequency band from 515 to 600 GHz. It has a measured double-sideband noise temperature as low as 1300 K at room temperature, which makes it a sensitive receiver for applications where cryogenic cooling can’t be used. In this paper, the results of the performance tests will be presented. This includes noise temperature measurements across the receiver band, Allan-time stability measurements, and beam pattern measurements. Finally we will present the performance of the receiver when used for molecular spectroscopy of CH3OH with a digital Fast Fourier transform spectrometer as back-end.

[1] Terahertz heterodyne receiver components for future European space missions (242424) - www.fp7-teracomp.eu