A Large Field-of-View Focal Plane Array based on Zernike Freeform Surface

Applications of passive millimeter waves (PMMWs), especially PMMW imaging and PMMW radar, are required in medicine, homeland security, communication, and space technology, but constrained by the limited field-of-view (FoV) of focal plane array (FPA). In this paper, the influence of feed antenna tilt on antenna gain is investigated theoretically, and a forward free-form surface optimization method to expand FoV is proposed, thereby designing a wide-scan MMW focal plane array with a free-form surface reflector, which provides a high antenna gain of 46.5dB. The staggered placement of feed antennas achieves a 3dB effective isotropic radiated power (EIRP) within a relatively large field of view, up to +/-18.7 degrees. The FPA uses a paraboloid-based Zernike freeform reflector that optimizes the illumination of the far field region according to the feed pattern. In this way, we could improve the FoV and increase feed elements of the system without worrying about coupling efficiency between the focus field and single mode feed antenna.