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The Yuan Tseh Lee Array (YTLA, formerly AMiBA)
| 1.2 m Shielded Cassegrain Antenna for Close-Packed Radio Interferometer |
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Image Credit: Koch et al.
Left: Contour plot of the antenna beam pattern measured in the far field. The units are in decibels. The cross-structure around the secondary sidelobes is likely to result from scattering of the secondary-mirror support structure. Right: One-dimensional scans, extracted from the left panel, parallel to the x- and y-axes after location of the main beam maximum. Overlaid is the simulation result for the E-plane at 95 GHz.
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| The 1.2m dish far-field beam pattern was measured with a computer-controlled equatorial mount, scanning a fixed 90 GHz thermally stabilized CW source at a distance of about 250-300m. An example of a measured beam pattern from a 2-dimensional scan is shown in the left panel. A cross-like feature likely resulting from the four legs of the secondary mirror support structure becomes apparent, with an increase in power of about 1dB at the location of the second sidelobe. The right panel compares two orthogonal scans across the main beam center with the expected theoretical simulation result for the E-plane at 95 GHz. From the measurement, a FWHM of about 11 arcmin is found with a first sidelobe peaking at about -16 to -18dB. (Koch et al., 2011, PASP, 123, 198) |
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