Numerical study of a UWB dual-polarized feed design for enhanced tapered chambers

A tapered chamber is a facility to provide the quiet zone environment necessary for the accurate measurement of antenna radiation patterns and the radar cross sections (RCS) of targets. A crucial aspect to be considered in any tapered chamber design is that the launching field (feed) antenna should provide a uniform amplitude and phase distribution throughout the test zone. A novel wave launcher design for an enhanced tapered chamber is discussed to provide both ultra wideband (UWB) and dual polarization capabilities. The enhanced tapered chamber feed antenna uses a dual-polarized aperture-matched UWB bow-tie antenna. We investigate its performance by means of a detailed finite-difference time-domain (FDTD) model which incorporates the absorber material characteristics, the feeding cable structures, and the complete geometry of the wave launcher and feeding section of the chamber. The FDTD results show that, for the physical dimension considered, the frequency of operation can be as low as 300 MHz, for a tolerance of 5 dB in the aperture electric field magnitude variations in the test zone. This feed antenna design can be applied to fully extended tapered chambers used in wireless antenna testing and RCS measurements.