A Dynamic Dual Reflector Antenna for 4-D Synthetic Aperture Radar Imaging Achieving a 0.4° Pencil Beam at 77 GHz

Abstract

All existing state-of-the-art high-resolution millimeter-wave imaging systems experience a tradeoff between image acquisition time and transceiver array complexity. The proposed dual-reflector antenna breaks this tradeoff by drastically reducing the array formation time while maintaining the relative simplicity that comes with using a single transceiver element. It consists of a dual-mode horn feed, a rotating ellipsoidal subreflector, and a conic main reflector. The rotating subreflector creates a virtual phase center that rotates about an axis to produce a synthetic circular array with a diameter of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$120\lambda $ </tex-math></inline-formula> . The main reflector redirects the beams from each of these virtual phase centers to overlap and illuminate the scene over a wide field of view (FOV). Two cases are simulated, one with a 14° FOV and another with 25° FOV in both azimuth and elevation. The former case is experimentally verified and achieves a measured half-power beamwidth of 0.4° over the entire scan range. The proposed system can reduce the image acquisition time to the order of milliseconds/seconds, which makes real-time SAR imaging a practical alternative to multiple-input–multiple-output (MIMO) and phased arrays at millimeter-wave and sub-millimeter-wave frequencies.