Compact mechanically scanned antennas for real-time passive-millimetre-wave imaging

The paper describes a novel reflective lens for use at millimetre and micro wave frequencies. This lens uses twist-polarisation techniques and consists of two wire grid polarisers and a Faraday rotator. The authors also discus s how a high-speed rotary scanning mechanism can be used to produce a linea r scan pattern, again using twist-polarisation techniques. This linear scan ner employs a wire grid polariser in the form of a roof prism, a rotating d isc inclined with respect to its axis of rotation and a Faraday rotator or quarter-wave plate. This scanner may be used with the novel reflective lens to form the basis of a real-time imager. A more compact design uses just t he lens and rotating disc and has been demonstrated in a real-time passive- millimetre-wave imager.