A New and Efficient UTD Based Near Field Scanning Technique for Antenna Radiation Pattern Analysis

Abstract

A new method is presented for computing far field antenna patterns from spherical near field antenna measurement data. The method utilizes a novel Uniform Geometrical Theory of Diffraction(UTD) based transformation of spherically scanned antenna tangential electric (or magnetic) near field measured values to present to obtain the antenna far field more efficiently. If the measured tangential near fields on the spherical measurement surface S which completely encloses the antenna under test(AUT) are only of the electric type, then the field external to S can be expressed, via an appropriate equivalence theorem, directly as the field produced by an equivalent magnetic surface current source distribution on S that is now made into a perfect electric conductor(PEC). The equivalent magnetic surface current density on the PEC sphere S (PECS) is exactly related to the measured tangential electric field on the original surface S. The field external to the PECS due to an equivalent magnetic surface current distribution on the same PECS can thus be expressed as an integral of the dot product of an appropriate dyadic Green′s function. A highly accurate and relatively simple asymptotic high frequency UTD form of this special dyadic Green′s function is available in essentially closed form. Examples illustrating the accuracy and speed of UTD based spherical near to far field transformations for large to moderately large antennas are presented.