Base Band Data for Testing Interference Mitigation Algorithms

Jon F. Bell, Peter J. Hall, Warwick E. Wilson, Robert
J. Sault,
\\ Rick J. Smegal, Malcolm R. Smith, Willem van Straten, \\
Michael J. Kesteven, Richard H. Ferris, Frank H. Briggs, \\
Graham J. Carrad, Malcom W. Sinclair, Russell G. Gough, \\
John M. Sarkissian, John D. Bunton \& Matthew Bailes, PASA, 18 (1), in press.

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Reference Antenna

Many interference mitigation algorithms are limited by how well the interfering signals can be characterised and, in practice this depends on the interference-to-noise ratio (INR). Mostly the interfering signals are received through the 0dBi side lobes of parabolic dish radio telescopes, or side lobes of the feed systems. One way to obtain a higher INR is to use a reference antenna with a gain somewhat higher than the 0dBi dish side lobes. We obtained an old 1400 MHz band horn with a 60⁰ beam width and gain of 10 dBi that was once used to illuminate the CSIRO ATNF Parkes dish. This was coupled to a transition and some borrowed ambient-temperature RF amplifiers. The system temperature of the completed package determined from hot and cold load measurements, is 450 K (dominated by the amplifiers). Other details of the system perfomance are given in Table 1. Our packaging of the feed and electronics is somewhat unusual in that the assembly is housed in a plastic bucket, earning the reference front-end the appellation ``bucket receiver'' (see Figure 2a & 2b). The improved INR obtained with the reference receiver is clearly shown in Figure 3. Far from being a state of the art system, the reference receiver is a low-cost first prototype.

Table 1: Properties of the reference antenna

Frequency (MHz)	1400-1600
Gain (dBi)	10
System temperature (K)	450
Nominal amplifier noise Figure (K)	360
Beam width (degrees)	60
Polarisation isolation (dB)	-20
Return loss (dB)	-15
Noise coupling (dB)	-35

**Figure 2:** Pictures of the reference receiver (a) Top left: Uncooled front end amplifier system (b) Top right: Water proofed for outside use and ready to go !
$\begin{figure} \centering\leavevmode \epsfxsize=0.45\columnwidth \epsfbox{buck... ....ps} \epsfxsize=0.45\columnwidth \epsfbox{buckets_receiver7.ps} \end{figure}$

**Figure 3:** Averaged autocorrelation spectra from SRT005_02 centered on 1499 MHz with 512 spectral bins across the 5MHz band width. The top 2 panels show 2 linear polarisations from the centre beam of the multibeam. The bottom 2 panels show 2 linear polarisations from the reference receiver. In all cases the vertical axes are amplitude and the horizontal axes are spectral bins.
$\begin{figure} \centering\leavevmode \epsfxsize=\columnwidth \epsfbox{Parkes2.ps} \end{figure}$

Next Section: Description of available data
Title/Abstract Page: Base Band Data for
Previous Section: Properties of Interfering Signals
Contents Page: Volume 18, Number 1

ASKAP

Public

Australia Telescope National Facility

Reference Antenna