Plextek Limited

Steve Greendale

David Spreadbury

Graham Pearson

Mark Radford

Electronically steered radar systems such as frequency scanning radars are particularly suitable for detecting and monitoring slow moving, ground-based targets. So-called crawler radar systems are intended for detection of targets that deliberately attempt to avoid detection by keeping low and by moving slowly. Disclosed is a radar system which includes an electronically steered antenna and a receiver arranged to process signals received from a target located at a distance from the radar system so as to identify a Doppler frequency associated with the target. The antenna stares at, rather than glides past, the target surrounding clutter. This means that the spectral spreading of static ground clutter associated with mechanical radar systems can be eliminated, overcoming one of the shortcomings of mechanical radar systems that would otherwise render a crawler radar system unsuitable for Doppler processing.

Radar system

A scanning radar system suitable for detecting and monitoring ground-based targets includes a frequency generator, a frequency scanning antenna, and a receiver arranged to process signals received from a target so as to identify a Doppler frequency associated with the target. The frequency generator generates sets of signals, each set having a different characteristic frequency, and includes a digital synthesiser arranged to modulate a continuous wave signal of a given characteristic frequency by a sequence of modulation patterns to generate one set of signals. The frequency scanning antenna cooperates with the frequency generator to transceive radiation over a region having an angular extent dependent on the generated frequencies. Digital synthesiser techniques capable of precise frequency generation and control are combined with passive frequency scanning and Doppler processing techniques, enabling accurate control of range and scan rates, and optimisation of range cell size for factors such as slow and fast target detection and Signal to Noise ratio, so that targets can be detected at distances considerably farther away than is possible with known systems having similar power requirements.

Embodiments of the invention are concerned with a radar system, and relates specifically to scanning radar systems that are suitable for detecting and monitoring ground-based targets. In one aspect, the radar system is embodied as a scanning radar system comprising a frequency generator, a frequency scanning antenna, and a receiver arranged to process signals received from a target so as to identify a Doppler frequency associated with the target, wherein the frequency generator is arranged to generate a plurality of sets of signals, each set having a different characteristic frequency, the frequency generator comprising a digital synthesiser arranged to modulate a continuous wave signal of a given characteristic frequency by a sequence of modulation of patterns whereby to generate a said set of signals, and wherein the frequency scanning antenna is arranged to cooperate with the frequency generator so as to transceive radiation over a region having an angular extent dependent on the said generated frequencies. Embodiments of the invention thus combine digital synthesiser techniques, which are capable of precise frequency generation and control, with passive frequency scanning and Doppler processing techniques. This enables accurate control of range and of scan rates, and enables optimisation of range cell size for factors such as slow and fast target detection and Signal to Noise ratio, and thus enables detection of targets located at distances considerably farther away than is possible with known systems having similar power requirements.

Growing community of inventors

Cambridge, United Kingdom

Steve Greendale