Experimental estimation of the petalled antenna system characteristics

Abstract

Methods of the antenna system (AS) characteristics determination by the field measuring in the near zone are widely used now. Advantages of near-field methods are obvious when it is necessary to obtain a detail information about antenna characteristics and to tune a number of similar antennas. In the last case it is possible to tune an antenna by comparing the results of measuring the amplitude and phase distribution (APD) in the near zone of the standard antenna and tested one, without measuring the field in the far zone.

An automatic complex was designed for the estimation of a serial AS tuning opportunities based on the results of measurements in the near zone. It allowed to measure the APD of the antenna near-field on the flat surface and to calculate their characteristics.

Experimental study was performed for a paraboloidal petalled AS of satellite television which was designed by NPO «Saturn». The main purpose of experimental investigations was to measure the APD of the near-field, tune the AS, calculate antenna characteristics in the far zone, and compare calculated and measured values in the far zone.

Antenna aperture and scanning plane were parallel during the measurements. Measurements were made on three frequencies. The analysis of obtained phase distribution plots shows that the current distribution on the aperture is in phase, possesses a random symmetry and may be approximated by a square-law function.

To tune the antenna the feed was displaced along the focal axis, and the measurements of APD were made in two ortogonal planes. The optimum position of the feed was found from the results of measurements, and the obtained APD was used to calculate the antenna pattern

These investigations have shown a high efficiency of the application of near-field methods for real-time estimation of AS characteristics and tuning. In certain cases, it enables one to eliminate measurements in the far zone.