The Council for Scientific and Industrial Research’s (CSIR’s) Electronic Warfare (EW) team is focused on increasing the maturity of its Digital Radio Frequency Memory (DRFM) technology.

Radar and EW systems detect, track, measure, identify, protect and implement counter- measures for sensors operating in the microwave spectrum, CSIR principal systems engineer of experimental EW systems Klasie Olivier explains.

The CSIR’s EW team uses its DRFM technology for testing and evaluating EW and radar equipment in support of industrial and scienti- fic development on its own, as well as in partner- ship with principals from the public and private sectors, in line with the CSIR’s mandate.

“We have our own in-house radar development capability and we assist our radar colleagues by testing radars and assisting with radar development,” Olivier states.

“Currently, we are evaluating the typical performance specifications of the DRFM bandwidth and developing the next generation of DRFM, for which we are aiming towards 2 GHz instantaneous bandwidth – a significant improvement on the current 800 MHz,” says Olivier.

“We aim to complete this concept demonstrator by the second quarter of 2013.”

DRFM technology has continuously been improved to ensure its effectiveness, says CSIR EW team applications principal engineer Warren du Plessis.

The most significant improvement made to this technology since its inception in the 1980s has been the addition of a Field-Programmable Gate Array (FPGA) to the DRFM data path in 2007, which allows wideband real-time signal processing.

“This was a revolutionary improvement, as it made the technology more versatile,” Du Plessis notes, adding that EW researchers are constantly improving the technology to ensure its competitiveness.

DRFM Uses
CSIR radio frequency, radar and EW sys- tems engineer Johann de Jager explains that modern radars emit pulses that contain information which is captured and manipu- lated by DRFM technology to confuse an adversary.

When a radar sends out a pulse to monitor the external environment, such as the ocean surrounding a ship, that pulse can be captured by another vessel through the use of DRFM. It can then be manipulated and sent back to the radar.

The radar then performs processing on the received pulse, which assists in identifying whether a possible target, such as a ship or a helicopter, is nearby or approaching.

“Radar technology is well advanced and radar experts can provide the speed and distance of a target, depending on the information it receives back from the pulse it emitted,” De Jager states.

DRFM technology captures the pulses emitted by radars, digitises the information with an analogue-to-digital converter (ADC) and then manipulates the data so that the information received by a radar will not reveal the actual target’s position and other characteristics.

“We can process the captured information and manipulate the radar pulse to represent what we want it to represent so that the radar under evaluation will see only what we simulate,” he notes.

When a radar operator looks at the display of the manipulated pulse, he or she will not be able to tell that the image on display is only a simulated one and not the actual one. For example, the operator will think it is a real target that is moving away when it is actually approaching.

However, as a result of modern technology, radar can detect whether a DRFM system is creating a target by analysing the pulse it receives, says CSIR systems engineer of radar and EW systems Danny Naicker.

As a result, when we capture a pulse transmitted by radar, we have to make the image we want the pulse to project as realistic as possible.

Actual targets, such as ships or aircraft, produce radar cross section fluctuations and we need to replicate that phenomenon by using complex-scatterer technology so that the pulse we send back to the radar projects a realistic target, he explains.

“This is why technological improvement is critical in areas such as ADCs and firmware development on FPGAs,” Naicker stresses.

“It is a cat-and-mouse game. Radar researchers keep improving radar technology, which enables them to increase their sense of awareness, and the EW researchers keep improving our DRFM technology to provide an acceptable return signal to the radar for detection purposes, but which may be a false return in terms of the real position or other characteristics of the target of interest,” says Olivier.

Further, De Jager states that the CSIR holds a major advantage over global competitors because its EW and radar teams are situated in the same building. This allows researchers and engineers to adapt, compete and compare DRFM and radar technologies, while working together in ensuring that South Africa’s technology base remains among the best in the world.
Olivier adds that the CSIR is one of the few organisations that is able to produce mixed signal layouts on single printed circuit boards with the performance required for this demanding application.

“Mixed signal design is challenging, as you are mixing sensitive analogue and noisy digital signals on the same hardware platform, says Naicker, adding that the CSIR’s DRFM technology has evolved to being more than a typical DRFM.

The technology has been adapted and advanced to work as an EW receiver, a radar transmitter, a DRFM and a radar, he explains.

“The main limit with this technology is your imagination,” Du Plessis states.

CSIR Supporting the MeerKAT
Meanwhile, the CSIR states that its radar experts assisted engineers from the Square Kilometre Array (SKA) project in the characterisation of a wideband ADC for integration into the Karoo Array Telescope (MeerKAT) antennas as a component of the L-band frequency (0.9 – 1.67 GHz) upgrade that is currently under way.

The CSIR performed the characterisation of the ADC, providing the team with an evaluation performed at the intended sampling speed it would use in determining the attain- able performance levels of the eventual system.

With the measured results in hand, the SKA team had the necessary confidence to proceed with designing this ADC for integration into the MeerKAT, the CSIR states.

The MeerKAT is a midfrequency radio telescope and is considered a forerunner to the SKA. It will be the largest and most sensitive radio telescope in the southern hemisphere until the SKA is completed by about 2024.

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