Abstract-Quad ridge horn antennas of various geometries are considered as possible candidates for a wideband reflector antenna feed. It is demonstrated that shaping the sidewalls of the ridge horns significantly improves the radiation characteristics of the horns. The conical quad ridge horn with an elliptically shaped sidewall shows the most promise as a wideband reflector antenna feed. The radiation patterns are rotationally symmetric and the 10 dB beamwidth is reasonably constant over a wide frequency range.Index Terms-Radio astronomy, horn antenna, reflector antenna, wideband, dual polarization.

Abstract-A quad-ridge horn antenna is presented as a feed for a reflector antenna for use in radio astronomy applications. The antenna uses elliptically shaped sidewalls to limit the variation of beamwidth over a wide frequency range and to obtain greater radiation pattern rotational symmetry. The antenna is dual-polarized and matched over more than a 4:1 bandwidth. A design procedure is presented and a prototype designed according to this procedure is shown. Measured and simulated results of the prototype correspond well. The antenna is analyzed with a prime focus reflector to determine the range of efficiencies that can be expected.Index Terms-Radio astronomy, horn antennas, reflector antennas, broadband, antenna feeds.

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The conductivity of a number of mechanical surface finishes are compared to determine if they are suitable for low loss components such as horn antennas and waveguides that are to be used in radio astronomy.

This paper describes the design and measured performance of the band 2 (L-band, 950 MHz-1760 MHz) cryogenic receiver front-end of the Square Kilometre Array (SKA) radio telescope dish array. The system comprises a wide flare-angle axially corrugated conical horn, a dual linearly polarized orthogonal mode transduce, a noise injection directional coupler, and two amplification stages. Its compact design and cryogenic cooling allow for a very low receiver noise temperature, and it presents another step in the continuous improvement of the noise temperature performance. A Gifford-McMahon cooler physically cools the OMT with its integrated directional coupler to around 70 K, and the first stage low-noise amplifier to about 15 K. A bespoke measurement setup was designed to measure the system's performance. The measured receiver noise is about 6 K across the frequency band.