The Council for Scientific and Industrial Research (CSIR) aims to expand its pioneering passive radar research over the next few years and add more receivers to its network.
This is according to Francois Maasdorp, an engineer at the Council for Scientific and Industrial Research (CSIR), who was speaking at the Aardvark Roost Electronic Warfare South Africa 2017 Conference and Exhibition on 8 November.
Passive radar technology is being developed in South Africa by the CSIR, academic institutions (the University of Pretoria and University of Cape Town) and private companies (Peralex Electronics and Lochtron) as well as Armscor, which is providing funding and support.
Prototypes have been built and tested from 2013. In the Western Cape, passive radar receivers were able to detect large airliners at bistatic ranges of 500 km and also detect and track a Cessna 208 light aircraft. A test in Gauteng in 2013 was able to detect a Cessna 172 aircraft flying at 2 000 feet above ground level at a bistatic range of 168 km and accurately predict the revolutions per minute of the aircraft’s propeller. These tests were done by using FM radio transmissions as the illuminator of opportunity. There are currently passive radar receivers at the CSIR and South African National Space Agency Space Operations.
Maasdorp said the CSIR is currently developing a passive radar testbed facility to exploit FM radio in Africa over the next three years and will eventually have six passive radar receivers, with a central node in Gauteng that combines all the receiver information and tracks aircraft. The central node will also collect Air Traffic and Navigation Services (ATNS) and automatic dependent surveillance – broadcast (ADS–B) data to allow for a direct comparison in passive radar tracking and traditional radar tracking.
The CSIR is also working on using passive radar to detect and track small unmanned aerial vehicles (UAVs), using DVB-H (Digital Video Broadcasting – Handheld) television signals. Using these short-range signals, the CSIR was able to detect a DJI Phantom small UAV in a test conducted at the CSIR’s facilities in Pretoria.
Unlike traditional radar, passive radar only needs a receiver to detect signals emitted by other sources, such as FM radio towers, TV transmitters, WiFi and weather radar. This makes passive radar (also known as passive coherent location, passive bistatic radar, piggyback radar and covert radar) cost effective, safe (no emissions) and highly mobile. By using several antennas one can use triangulation to identify the location of an aircraft, or by using a single receiver one can use the angle of arrival of the signal to determine a target’s location.
One of the benefits of passive radar is that it is covert, as it does not rely on a transmitter that can be detected and destroyed. Furthermore, it is possible to detect stealth aircraft using passive radar by measuring distortions and disturbances in the soup of signals in the atmosphere, or certain frequencies that stealth aircraft cannot absorb. There are many useful applications for passive radar, such as border safeguarding, air traffic control (ATC) support etc.
The market for passive radar is still in its infancy with only a few systems available on the market, but a number of countries and institutions are working on the technology. Maasdorp said there are so few systems deployed mainly due to the fact that passive radar is an emerging technology and there is little data on its performance over long periods, for example months.
Passive radar is difficult to jam as it would require enormous power to jam all transmitters in an area, but Francois Schonken, Chief Research Fellow at the University of Cape Town, noted that electronic countermeasures can be applied against passive radar. He notes that noise jamming can impede the performance of a passive radar picking up FM radio signals, when the location of the receiver is known. Future endeavours may look at introducing false targets to confuse passive radar.