Full-spherical radiation pattern evaluation of low frequency antennas using a novel very-near-field electro-optical system

Abstract

An efficient 3-D radiation pattern and gain measurement technique for low frequency antennas using very-near-field mapping is presented. The tangential electric fields of an antenna under test (AUT) at surfaces enclosing the antenna are accurately measured by a unique measurement system with a non-intrusive electro-optical (EO) probe, eliminating the need for costly large anechoic chamber facilities. We also develop a simple near-field to far-field transformation method to derive exact far-field quantities of the AUT. This method can provide the full spherical radiation pattern and gain of all types of antennas without any truncation errors. To demonstrate the proposed approach, a low-VHF folded dipole [1] is employed. The measured results agree very well with simulation results and those obtained from far-field measurement performed in an outdoor range.