The Design of Large Aperture Terahertz Tri-reflector CATR with Spherical Main-mirror

This paper introduces a design of large aperture tri-reflector compact antenna test range (CATR) with spherical main-mirror which is working in the Terahertz range. The diameter of the main mirror is 2 m, and the dimensions of the two shaped sub mirrors are about 0.6 m and 0.7 m respectively. The dimensions of the two sub mirrors are far smaller than the aperture side length of the main mirror. According to the characteristics of geometric optics and frequency-independent, we use kinematic and dynamic ray tracing method to design two shaped sub-reflectors. The system of reflectors is configured in a Cassegrain-Gregorian arrangement. Through the above design method, the CATR can generate a regional pseudoplane wave, usually referred to as quiet zone (QZ), and we can get the expected output field distribution in the quiet zone. By numerical analysis and simulation verification, we can see that a peak-to-peak amplitude (phase) ripple <; 1 dB (10°) and a cross-polarization isolation > 30 dB can be achieved on the principal cuts of the designed quiet zone at 100-300 GHz. At the same time, the QZ usage ratio of the CATR can reach 70%. The proposed tri-reflector CATR has a good quiet zone performance and high QZ usage ratio, so it can be used in large aperture antenna measurements.