At the recent ILA Berlin Airshow, Airbus Defence & Space reported progress with the passive radar [alternatively, passive coherent location (PCL)] system that predecessor company Cassidian had been developing since 2006. Frank Bernhardt, project manager, said that the company has “worked closely” with two armed forces on tests of the system. One of them is Germany. Airbus D&S has also gained a study contract with the UK Civil Aviation Authority to explore the ATC applications of passive radar.

Bernhardt reported that a second sensor van was added to the system last year, thus providing more ellipsoids and improving accuracy. The system has been adapted to work with DAB+ signals, with DVB-T2 to come. “I believe we are still the only ones to have fused three bands,” he added. The system can process eight FM transmitters, plus one each of DAB+ and DVB-T. Airbus D&S claims a detection range of up to 200 km (FM) for larger aircraft, and an accuracy of 10 m (DAB/DVB-T). The recent test used two light aircraft and a Learjet 35 as targets.

The attractions of passive radar are many, according to Bernhardt. “You don’t know where it is, you don’t know how many [detectors] there are and you can’t jam it,” he said. “There’s no turning radar antenna, so we spend 100 percent time-on-target, with an update rate of 0.5 seconds instead of six seconds,” he continued. “Moreover, there is no need to secure frequency allocation and approval from governments,” he added.

The UK CAA is interested in the potential for passive radar to release precious bandwidth for other uses, Bernhardt said. The new contract will also explore how the system could be placed in built-up areas without creating emissions, unlike a radar system.

According to Airbus D&S, several cost-effective passive-radar sensors using a number of emitters could broaden the basis for detection of aircraft approaching an airport. Placing several such sensors intelligently could also eliminate the problem of confusing echoes and interference from the increasing number of wind farms that are afflicting conventional ATC radars, the company added. Interestingly, since the system needs no cooperation from aircraft transponders, it might have provided clues to the fate of Malaysia Airlines Flight MH370, had it been deployed in the relevant area.