An optical feed for high resolution passive millimetre wave imaging systems

The authors discuss two methods to improve the spatial resolution of millimetre wave imagers. One employs a large primary aperture, a 1.4 m square primary reflector, and the other enhances the resulting images using superresolution techniques. These later techniques effectively boost the high spatial frequency content in the image, thereby sharpening the perceived antenna far field pattern. It is usual in radar applications to taper the primary aperture distribution in order to suppress sidelobes. Such a distribution if used in millimetre wave imaging would result in a loss of the high spatial frequencies required by the superresolution algorithms. In the first section they show why a rectangular aperture distribution is preferred and how this can be achieved by relaying a uniform feed distribution onto the primary reflector using millimetre wave optics. Such relaying techniques have been demonstrated on their 35 GHz imaging system and the resulting imagery is illustrated in the final section