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THACO: A Test Facility for Characterizing the Noise Performance of Active Antenna Arrays

Submitter: Bert Woestenburg
Description: Recently, the THot And COld (THACO) facility on the test platform near the Dwingeloo telescope has been characterized for measuring the noise performance of small aperture arrays in the 1-2 GHz frequency range. The principle of the noise measurement is the hot/cold Y-factor method.

As the picture shows, THACO consists of a metal funnel with a removable roof. The latter is covered with absorbing material to serve as the (300K) ‘hot load’. The roof may be moved away on a short rail track, in order to expose the array to the sky for the ‘cold load’ measurement. The funnel itself is meant to provide shielding from RFI and other noise from the environment.

The figure shows a comparison of array noise temperatures for two small arrays with 4 (2x2) and 16 (4x4) active elements, measured inside and outside the THACO funnel, and compared to simulation results for a full 49-element (7x7) array. The beneficial effect of shielding environmental noise (trees, buildings) is clearly visible.

The conclusion is that the results for the small active arrays inside THACO accurately represent the performance of larger antenna arrays. It is therefore not necessary to build and test large arrays to assess their noise properties.

More details on these measurements may be found in a paper on THACO, that will be presented at the European Microwave Conference in Manchester in October.
Copyright: ASTRON
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