Q-band receiver system design for the Canadian DVA-2 radio telescope

Abstract

A compact front-end system is presented for a dual-linear polarization cryogenic Q-band receiver. This receiver will be used to demonstrate the high frequency performance of the Dish Verification Antenna 2 (DVA-2) composite reflector telescope between 35–50 GHz and is a technology demonstrator with possible application to the National Radio Astronomy Observatory’s Next Generation Very Large Array (ngVLA). A vacuum vessel and a two-stage Gifford-McMahon cryopump system are used for the cryogenic environment. The second stage of the cryostat is cooled to 16 K and includes a small choke ring feed horn, a low-loss noise calibration module (NCM) integrated with orthogonal mode transducer (OMT), and two cryogenically cooled mHEMT MMIC low-noise amplifiers (LNAs). Using a noise diode as the noise source on the 300 K stage inside the cryostat helps to protect the cooled components from signals outside of the cryostat, and also lessen the heat on the second stage since a noise diode normally produce a power dissipation of several hundred mW. The OMT design is an optimized version of the design used in the ALMA Band 1 cartridge with two integrated directional couplers and excellent performance. The cascaded noise analysis of the receiver shows a receiver noise temperature of 19.4 K.