STEWART PENNEY / EDINBURGH
Process involves commercial-off-the-shelf computing
BAE Systems Avionics has developed a way of improving the resolution of mechanically scanned radars that uses commercial-off-the-shelf (COTS) computing and will allow continued improvement as microprocessor performance advances. This is the first time that radar resolution has been linked to the rapid improvement in commercial computing speeds, according to BAE Avionics technical director Professor John Roulston.
The system allows 1m (3ft) or better resolution to be achieved with an X-band coherent-pulse radar operating in synthetic aperture radar (SAR) imaging mode. This can be offered as a technology insertion into in-service radars, says Roulston. The system provides a "higher resolution capability in conventional equipment", he adds.
Although some minor changes to the radar's analogue path would be made, "this technique removes most of the need", he says.
Improved resolution increases a radar's utility particularly in air-to-surface modes, but also air-to-air. BAE has demonstrated the system on a Blue Vixen radar, but it could be retrofitted to "any coherent radar of Western origin", says Roulston. As well as fighter radars such as Blue Vixen, the technology can also be incorporated in maritime systems such as the company's Blue Kestrel. He says a system could be operational within a year of an order - enough work has been done that "the risk is not the technology but just that of changing the equipment".
Roulston says by combining traditional gallium arsenide (GaAs) chips with silicon-based COTS processors, it is possible to boost a radar's resolution relatively simply.
The GaAs MIMIC (microwave monolithic integrated circuit) on the transmit side of the radar and the COTS-based system on the receive side "have to be tightly connected as they work in combination; the signals are a matched pair", he says, adding that, if the "signal out [transmitted] is altered then the signal in is altered".
He adds: "The performance of this system grows at the rate of performance growth of silicon-based chips. With microwave systems that doesn't necessarily happen."
Roulston says the technology will advance with computing improvements until resolution is improved to the practical maximum. For a typical X-band radar 3cm wavelength, in a damp atmosphere (radar propagation is affected by water droplets), Roulston believes resolution can be increased to 0.3m at 50km range. The determining factor will be "physical limits, not processing limits", he says.
Source: Flight International
