Design of a Coaxial Feed Horn for High Efficiency Compact Antenna Test Range

The aperture efficiency is an important parameter to evaluate working performance of compact antenna test range (CATR). High aperture efficiency means that the reflector with same size can obtain larger quiet zone (QZ) field, whose quality is designed by parameters such as amplitude ripple, phase ripple and cross-polarization level (CPL). coaxial feed horn can produce a shaped pattern that has been used to obtain a high aperture efficiency in the single parabolic reflector CATR. This coaxial feed horn has a transformable structure that consists of a central circular waveguide and is surrounded by one or more conductors with circular cross sections. When the number of rings in horn becomes larger, its aperture efficiency is also increase. However, the number of rings should be considered for reducing the difficulty of horn manufacture but keep the aperture efficiency of QZ having a good level. A two-rings structure of coaxial feed horn has been designed for larger QZ, which can obtain 80% aperture efficiency in a single parabolic reflector CATR.