On-board calibration system for millimeter-wave radiometers based on reference-polarized signal injection

This paper presents the architecture of a novel on-board calibration system for millimeter-wave radiometers aimed at measuring the Q,U Stokes parameters of the sky emission. This technique requires the injection of differently polarized reference signals, which is carried out by means of a specific component mounted in the antenna-feed system. The presented technique was developed by Cortiglioni et al. for the calibration of the Balloon-borne Radiometers for Sky Polarization Observations radiometers, specifically designed to measure the polarized sky emission by a correlation technique. A procedure for the accurate evaluation of the polarization state of the calibration signals is also reported. Numerical and experimental results are presented for the Ka-band calibrator in the operational conditions.