Broadband polarimeter receivers at 30 and 40 GHz for cosmic microwave background measurement

Abstract

Broadband radiometers at 30 and 40 GHz for QUIJOTE radio astronomy experiment are very sensitive receivers to perform scientific sky observations of the Cosmic Microwave Background (CMB). The aim of this experiment is the linear polarization percentage measurement of the received signals. Radiometers have cryogenically cooled Front-End Modules followed by room temperature amplification, correlation and detection modules. Their relative bandwidth is around 30%. There are 30 receivers (pixels) at 30 GHz and 29 receivers at 40 GHz. The radiometer scheme is based on two balanced branches, microwave correlation and direct detection. The manufactured receivers measure Stokes polarization parameters I, Q, and U simultaneously. This paper describes the principle of operation of polarimeter receivers, and present details of manufactured subsystems, integration and test results. Receivers integrate different technologies: waveguides, microstrip, Monolithic Microwave Integrated Circuits (MMIC) and active and passive devices. The receivers are currently under installation in El Teide Observatory, Tenerife (Canary Islands, Spain).