Amplitude methods of antenna characteristics determination

Abstract

Near-zone antenna parameters determination methods are based on a near-field amplitude and phase distributions (APD) measurements. It means carrying out measurements of amplitude and phase, or ortogonal components of the near-field at a chosen surface. Conducting of such measurements at microwave frequencies is very difficult. That is why investigation of antenna parameters determination methods by measuring only an amplitude distribution of near-field is a very actual task.

Two options of the amplitude methods of antenna characteristics determination that differ from each other by a presence or lack of the reference signal source are examined in the report. The accuracy of amplitude methods based on the holographic recording of the near-field distribution is estimated by the known accuracy of measuring radioholograms.

Methods of APD and antenna patterns (AP) retrieval by amplitude measurements (without using a reference phase sources) are based on rising the volume of initial information about the antenna near-field and using a priori information about the investigated antenna. They allow realizing the iteration process for the retrieval of APD and AP of investigated antennas.

In the paper a method of APD and phased antenna array (PAA) characteristics retrieval, by dynamic near-field amplitude measurements, is examined. The method is based on measuring the dynamic near-field by two probes when PAA works in the scanning regime, but only a single probe can be used when PAA is specially phased.

Mathematical model results, which enable one to estimate accuracy characteristics of proposed method, are presented. It is shown that accuracy of determination of PAA AP depends on the mutual positions of the antenna and measuring probes, initial guess of phase approximation and accuracy of dynamic near-field amplitude measuring. Conducted analysis resulted in recommendations which allowed to chose the conditions of measurements and processing. These conditions ensure a fast convergence of the iterative algorithms and acceptable accuracy of APD and PAA AP determination.