Surface accuracy of a large-scale compact antenna test range considering mechanism, metrology and alignment

A large compact range (CR) having a width of 23m and height of 16m that will generate a Φ15m quiet zone is presented. The antenna consists of 30 blocks and 76 serrated reflectors. Its mechanical accuracy is reflected in two aspects: surface precision and gap precision. In addition, the root-mean-square (RMS) surface accuracy should be less than or equal to 0.075mm for achieving the highest operating frequency of 40GHz, and the gaps between two segments should be controlled strictly to the tolerance of 0.4 ± 0.2mm for avoiding gap diffraction and compensating for inter-block interference due to thermal deformation. The surface accuracy in terms of mechanical structure, metrology and alignment approach is very tight. First, a high-accuracy honeycomb sandwich panel, anisotropic back structure and spatial parallel adjustment mechanism are introduced, and the error contributions of these three mechanisms are 0.03mm, 0.01mm and 0.005mm, respectively. Second, a measurement network based on laser tracker metrology was established, and the RMS error of the measurement system is controlled to 0.025mm through the optimization of the measuring stations and weighted coordinate regression. Third, an original alignment approach that divides the entire assembly into three key phases by marked point edge-constrained surface is proposed. By performing a few iterations of onsite adjustment, the reflectors were aligned in the prescribed positions, and the gap quality was controlled effectively. Finally, the on-site alignment of the large CR is introduced. The final antenna surface RMS accuracy was up to 0.054mm, and the gaps achieved the desired design index.