High resolution 4-D millimeter-wave imaging radar

A dual-reflector antenna, comprising:

• a main reflector having shape of a paraboloid, where the paraboloid is formed around a principal axis;
• a sub-reflector arranged in the paraboloid along the principal axis of the main reflector and is configured to rotate about the principal axis, wherein the sub-reflector has a shape of an ellipsoid that defines two foci for electromagnetic radiation incident thereon;
• a linear actuator drivably coupled to the sub-reflector and operable to tilt the sub-reflector in relation to the principal axis, wherein the ellipsoid of the sub-reflector defining a major axis and the major axis of the sub-reflector is tilted with respect to the principal axis of the main reflector while rotating about the principal axis;
• and
• a feed horn disposed along the principal axis at one of the two foci and operable to guide electromagnetic radiation towards the sub-reflector;
• and
• a controller interfaced with the main reflector and the sub-reflector, wherein the controller rotates the sub-reflector about the principal axis to emanate the electromagnetic radiation in a diverging beam from a set of virtual feed positions that form a first circle and are located behind the dual-reflector antenna, and subsequently change tilt angle between the main reflector and the sub-reflector to emanate the electromagnetic radiation from another set of virtual feed positions that form a second circle and are located behind the dual-reflector antenna, where the first circle has different diameter than the second circle, thereby generating a synthetic aperture image.