04 November 2015 by Guy Martin - defenceWeb
European defence giant Airbus Defence and Space is developing a passive radar system that will soon be available to customers.
Active radars have been around for decades but they have their disadvantages, according to Frank Bernhardt: Head of Programme: Passive Radar at Airbus Defence and Space Electronics. By emitting a signal, active radars give away their positions and although there are various ways in which they can try and avoid detection, this is a significant drawback. Other limitations are emitting radiation that can interfere with other signals or can violate health and safety rules (such as emitting in a built-up area).
The idea of passive radar technology has been around since the 1930s, with Robert Watson-Watt performing experiments in 1935. However, it was not until some 20 years ago that technology (especially computer power) matured enough for passive radar to become viable.
The first passive radar systems were bistatic – in other words, the transmitter and receiver were in different places. Modern passive radar uses any transmitter of opportunity to detect disturbances and reflections in electromagnetic signals in order to determine the position of an object. Bernhardt said that FM radio signals and digital video broadcasting signals are the main passive radar sensors as they are strong emitters good for air surveillance.
Bernhardt said that the resurgence of passive radar has come about because of the availability of advanced processing technology that requires huge computing power. Another driver is the fact that there are a lot more emitters out there, providing many more signals to work with – if there are no electromagnetic signals in the atmosphere, passive radar obviously cannot work.