D. MP Smith, P. Meyer, B. M Herbst

 

Abstract

Passive millimetre-wave (PMMW) imaging is a technique that detects thermal radiation emitted
and reflected by metallic and non-metallic objects. While visual and infra-red (IR) emissions
are attenuated by atmospheric constituents, PMMW emissions are transmitted, resulting in
consistent contrast between objects from day to night even in low-visibility conditions. The use
of a PMMW imaging system on an unmanned aerial vehicle (UAV) has applications for
airborne surveillance, but the size of the UAV precludes optical or mechanical scanning. One
solution is a long, thin antenna fitted under the UAV. This antenna has a narrow beam along the
plane perpendicular to the flight path, but a broad beam along the plane of the flight path blurs
the image, making it difficult to determine the position of objects or to differentiate between
objects. This paper proposes a technique of image reconstruction based on the Kalman filter to
reconstruct an accurate image of the target area from such a detected signal. It is shown that
given a simulated target area, the Kalman filter is able to reconstruct the image using the
measured antenna pattern to model the scanning process and reverse the blurring effect.