Broadband Evolutionary Optimisation of a Free Form Contour Defined Serrated Edge Compact Antenna Test Range

Modern evolutionary optimization techniques when used with efficient parallelized electromagnetic simulation algorithms provide a very effective strategy for the design of high-performance compact antenna test ranges that can be readily tailored to address specific measurement needs. This paper extends the authors previous studies to include far more general serrated edge reflector designs than have previously been considered that, for the first time, not only refine the serration profile, but also the envelope of the projected outline of the offset parabolic reflector. This paper presents results that illustrate the utility of this approach examining and comparing fully broadband optimized predicted CATR quiet-zone performances.

I. Introduction

The Compact Antenna Test Range (CATR) comprising a low gain feed illuminating an offset parabolic reflector is a very widely used approach for taking far-field antenna measurements at fixed range lengths that are very much less than those distances suggested by the Rayleigh far-field criteria [1]. Thus, the low-gain feed radiates a quasi-spherical wave which is, upon reflection by the parabolic reflector, transformed into a pseudo-TEM, i.e. plane, wave that propagates through the region of space in which the test antenna is situated. Early workers quickly identified that controlling and minimising the amount of field diffracted from the edges of the range reflector and that impinges into the zone that is used to test a given antenna under test (AUT) was crucial to the success of the measurement technique [1]. During the past fifty or so years since the first inception of this reduced range length far-field measurement test technique, two contrasting approaches to managing reflector edge diffraction have come to prominence. These are CATRs with serrated edge (SE) reflectors, and CATRs with blended rolled edge (BRE) reflectors where it has been shown that, [2], the quiet-zone (QZ) performance of CATR serrated edges are to rolled edges as Chebyshev filters are to Butterworth filters, i.e. more pass-band ripple but with a faster roll off. Although other options are available [1], they are generally far less commonly encountered.