A new 3 mm band receiver for the Onsala 20 m antenna

¹ Group for Advanced Receiver Development, Department of Earth and Space Sciences, Chalmers University of Technology, 412 96 Gothenburg, Sweden
e-mail: Victor.Belitsky@chalmers.se
² Department of Earth and Space Sciences, Chalmers University of Technology, Electronic Laboratory, Onsala Space Observatory, 439 92 Onsala, Sweden
³ Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, 439 92 Onsala, Sweden

Received: 22 December 2014
Accepted: 29 May 2015

Abstract

A new receiver for the Onsala 20 m antenna with the possibility of being equipped with 3 mm and 4 mm bands has been built and the 3 mm channel has been commissioned during the Spring 2014. For single-dish operation, the receiver uses an innovative on-source/off-source optical switch. In combination with additional optical components and within the same optical layout, the switch provides two calibration loads (for the 3 mm and 4 mm channels), sideband rejection measurement, and tuning possibilities. The optical layout of the receiver employs all cold (4 K) offset elliptical mirrors for both channels, whereas the on-off switch employs flat mirrors only. The 3 mm channel employs a sideband separation (2SB) dual polarization receiver with orthomode transducer (OMT), 4–8 GHz intermediate frequency (IF), x 2pol x upper and lower sidebands (USB + LSB). The cryostat has four optical windows made of high density polyethylene (HDPE) with anti-reflection corrugations, two for the signal and two for each frequency band cold load. The cryostat uses a two-stage cryocooler produced by Sumitomo HI RDK 408D2 with anti-vibration suspension of the cold-head to minimize impact of the vibrations on the receiver stability. The local oscillator (LO) system is based on a Gunn oscillator with aphase lock loop (PLL) and four mechanical tuners for broadband operation, providing independently tunable LO power for each polarization. This paper provides a technical description of the receiver and its technology and could be useful for instrumentation engineers and observers using the Onsala 20 m telescope.