Design and development of a high-performance passive millimeter-wave imager for aeronautical applications

Abstract

We describe a high performance optomechanically scanned millimeter-wave imager intended to monitor the ground movement of aircraft in adverse weather conditions. It employs two counter-rotating mirrors that are tilted about their axes of rotation. They simulate the linear scan of a single high speed, large aperture flapping mirror. When used with a linear receiver array, they can produce a 2-D scan of the scene at TV rates. In the present application, they were used with a single receiver and a large flapping mirror to produce a 2-D scan of the scene ±10 deg vertically and 60 deg horizontally. One of the rotating mirrors has a concave surface and acts as the focusing element in the imager. The two mirrors are driven from a single servo motor using timing belts and toothed pulleys. The flapping mirror is slaved to the motion of the rotating disks using an electronic cam. The single channel 94-GHz receiver consisted of an InP LNA followed by a down converter and a detector. The video output passes to an A/D converter and is displayed on a conventional PC. This system has virtually 100% transmission and can be used at any waveband.