Holographic measurement of the 26m HartRAO telescope
Date
2009-05-08T10:08:02Z
Authors
Klein, Benjamin
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Abstract
Microwave holography is a well established method of using the Fourier relationship between an antenna’s
current distribution and its complex beam-pattern to produce surface maps of large parabolic antennas. As
the final part of a surface upgrade, a holographic map of the HartRAO 26 m telescope was produced. This
showed that the surface has an RMS error of 0.45 mm. The measurement used a small reference dish to
correlate against and retrieve amplitude and phase values. Due to system phase instabilities, this dish had to
be attached to the measured antenna in order to enable sharing a high frequency local oscillator (LO). The
movement was modelled and corrected for. However, a slight distortion remained. It is recommended that,
either the LO distribution system is stabilised by using multiple PLLs or amplifiers and low loss cables are
used to enable moving the reference antenna to a stationary position.
Description
Keywords
Holography, Microwave, Phase-stabilisation