Measuring Noise Temperatures of Phased-Array Antennas for Astronomy at CSIRO

Abstract We describe the development of a noise-temperature testing capability for phased-array antennas operating in receive mode from 0.7 GHz to 1.8 GHz. Sampled voltages from each array port were recorded digitally as the zenith-pointing array under test was presented with three scenes: (1) a large microwave absorber at ambient temperature, (2) the unobstructed radio sky, and (3) broadband noise transmitted from a reference antenna centred over and pointed at the array under test. The recorded voltages were processed in software to calculate the beam equivalent noise temperature for a maximum signal-to-noise ratio beam steered at the zenith. We introduced the reference-antenna measurement to make noise measurements with reproducible, well-defined beams directed at the zenith and thereby at the centre of the absorber target. We applied a detailed model of cosmic and atmospheric contributions to the radio sky emission that we used as a noise-temperature reference. We also present a comprehensive analysis of measurement uncertainty including random and systematic effects. The key systematic effect was due to uncertainty in the beamformed antenna pattern and how efficiently it illuminates the absorber load. We achieved a combined uncertainty as low as 4 K for a 40 K measurement of beam equivalent noise temperature. The measurement and analysis techniques described in this paper were pursued to support noise-performance verification of prototype phased-array feeds for the Australian Square Kilometre Array Pathfinder telescope.

[1]  Michael A. Saunders,et al.  SNOPT: An SQP Algorithm for Large-Scale Constrained Optimization , 2005, SIAM Rev..

[2]  India,et al.  The Australia Telescope Compact Array Broadband Backend (CABB): Description & First Results ⋆ , 2011, 1105.3532.

[3]  D. J. Fixsen,et al.  THE TEMPERATURE OF THE COSMIC MICROWAVE BACKGROUND , 2009, 0911.1955.

[4]  R Mittra,et al.  Connected Patch Array Analysis Using the Characteristic Basis Function Method , 2011, IEEE Transactions on Antennas and Propagation.

[5]  Richard T. Schilizzi,et al.  The Square Kilometre Array , 2009, Proceedings of the IEEE.

[6]  Gordon J. Hurford,et al.  Radio Frequency Interference Excision Using Spectral‐Domain Statistics , 2007 .

[7]  Rob Maaskant,et al.  Unified Definitions of Efficiencies and System Noise Temperature for Receiving Antenna Arrays , 2010, IEEE Transactions on Antennas and Propagation.

[8]  Memo 111 SKADS Benchmark Scenario Design and Costing – 2 ( The SKA Phase 2 AA Scenario ) , 2008 .

[9]  Barry N. Taylor,et al.  Guidelines for Evaluating and Expressing the Uncertainty of Nist Measurement Results , 2017 .

[10]  David R. DeBoer,et al.  Australian SKA Pathfinder: A High-Dynamic Range Wide-Field of View Survey Telescope , 2009, Proceedings of the IEEE.

[11]  K. I. Kellermann,et al.  Preliminary Specifications for the Square Kilometre Array , 2008 .

[12]  Robert T. Nash,et al.  Beam Efficiency Limitations of Large Antennas , 1964, IEEE Transactions on Military Electronics.

[13]  Peter J Hall,et al.  Experimental Demonstration of Focal Plane Array Beamforming in a Prototype Radiotelescope , 2010, IEEE Transactions on Antennas and Propagation.

[14]  B. Widrow,et al.  Adaptive antenna systems , 1967 .

[15]  S. Applebaum,et al.  Adaptive arrays , 1976 .

[16]  A. T. Young.  Air mass and refraction. , 1994, Applied optics.

[17]  P. A. Fridman.  RFI excision using a higher order statistics analysis of the power spectrum , 2001 .

[18]  B. Jeffs,et al.  Efficiencies and System Temperature for a Beamforming Array , 2008, IEEE Antennas and Wireless Propagation Letters.

[19]  M. V. Ivashina,et al.  Experimental Results for the Sensitivity of a Low Noise Aperture Array Tile for the SKA , 2012, IEEE Transactions on Antennas and Propagation.

[20]  F. Kitaura,et al.  Bayesian power-spectrum inference for large-scale structure data , 2009, 0911.2493.

[21]  Max Tegmark,et al.  A model of diffuse Galactic radio emission from 10 MHz to 100 GHz , 2008, 0802.1525.

[22]  Y. Lo,et al.  Optimization of directivity and signal-to-noise ratio of an arbitrary antenna array , 1966 .

[23]  Maurice Clerc,et al.  Standard Particle Swarm Optimisation , 2012 .