QUIET Coherent Polarimeter Modules

The Q/U Imaging ExperimenT (QUIET) consists of a pair of radiometer arrays designed to measure the B-mode polarization of the Cosmic Microwave Background (CMB) at 44 GHz (Q-band) and 95 GHz (W-band) with 19 and 90 modules at each frequency. The architecture of both arrays is based on miniaturized coherent polarimeters using High Electron Mobility Transistor (HEMT) chips for amplification; QUIET is the largest coherent microwave array ever fielded. We describe the detector technology used in Phase I of QUIET and our efforts to improve both the W-band module design and the fundamental performance of the HEMT amplifiers. These technology developments have wide application in the field of radio astronomy.