This article is cited in 1 paper

Radiophysics

Measurement of the reflector antenna absorption at terahertz frequencies by the method of a balanced radiometer

S. V. Shitov, A. V. Uvarov, A. B. Ermakov, A. N. Vistavkin

Kotelnikov Institute of Radioengineering and Electronics of the Russian Academy of Sciences, Moscow

Abstract: The inherent noise of a prototype panel of the millimeter-wave telescope main reflector is measured at room temperature. A modulation radiometer based on a heterodyne detector with an input superconducting mixer and a balanced antenna switch is used. The noise temperature of the detector in the double-sideband mode equals 570 K at a local oscillator frequency of 842 GHz. The absorption factor of the aluminum panel calculated from the thermal radiation intensity is 0.31 $\pm$ 0.07%. This value is checked on samples made of phosphor bronze and stainless steel. The respective absorption factors are 0.41 $\pm$ 0.07 and 1.30 $\pm$ 0.07%, which are close to those obtained earlier for these materials using radiometers with direct-reading detectors. The wide dynamic range of the heterodyne detector simplifies calibration of the radiometer: there is no need to cool down the sensitive element below liquid helium temperature. A balanced switch of a new design makes it possible to radically suppress the influence of the background and take precision room-temperature measurements.

Received: 22.03.2011

 English version: Technical Physics, 2011, 56:11, 1652–1660

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