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SIGNAL Executive Video: Expanding EW/Countermeasure System Capability With Direct RF

Direct radio frequency (RF) is the process of turning even ultra-high frequency analogue radio transmissions like those in Ka band directly into digital signals, without the need for an analogue “step down” and the accompanying cumbersome hardware requirements.

Bob Sgandurra, director of product management for Mercury Systems, explains in this Executive Video with SIGNAL Media how a new generation of direct RF offers unique capabilities for radar, electronic warfare, signals intelligence and communications.

Legacy systems, reliant on a prior generation of digital sampling technology, had to use cumbersome analogue equipment to “step down” high frequency signals so they could be sampled and digitized by converters that could only sample about four to six giga samples per second (GSPS), and therefore could handle analog signal frequencies no higher than six GHz. Signals in the Ka band, a high bandwidth frequency range used by communications satellites and radar equipment, range from 26.5 to 40 GHz.

For more than a decade now, Sgandurra said, direct RF technology has been sampling analogue signals with growing speed, gradually climbing up the GHz dial and able to handle increasingly high frequency transmissions without the need for any cumbersome analogue downshifting.

“Today, we’re sampling at 10 times that” four to six GSPS rate, he said during the interview. Now, a new generation of direct RF technology capable of digitizing even the ultra-high frequencies of the Ka band is deeply integrated with the latest hardware, he added.

Data converters were being packaged in hardware right alongside the customizable chips used in RF equipment, called Field Programmable Gateway Arrays or FPGA, Sgandurra said. “That intimate connection between the data converter and the FPGA fabric gives you a very low latency path,” which was vital in certain applications.





In electronic countermeasures, for instance, there is “a very small time window” during which the application must receive, process and retransmit. The low latency possible with direct RF “brings that advantage,” Sgandurra said.

Other advantages of direct RF include:

  • Size, weight and power (SWAP.) Analogue stepdown hardware is big and power hungry, especially in hardware like a phased array or electronically steerable antenna, where each of the hundreds or thousands of antenna elements is a channel that requires data conversion. ”You can see the SWAP savings pretty quickly,” Sgandurra said.
  • Operations and maintenance (O&M). By eliminating that stepdown equipment, you remove analogue components that will likely “drift in frequency or in phase over time and temperature,” and eventually age over time and requirement replacement, he said. ”So you're also lowering maintenance costs.”
  • A wide stare. Higher frequency sampling in new-generation direct RF technology enables it to look at a much wider bandwidth than analogue or legacy direct RF equipment, which has to scan a narrow sliver of bandwidth across the spectrum, meaning it may easily miss a signal outside its tuning range. The latest direct RF technology enables applications where the target signal may be transient, frequency hopping. “You need to see all that and … acquire those signals,” he said.
  • A revolution in beamforming. That same wide bandwidth capability gives new generation direct RF technology transformative functionality on the transmit side as well, Sgandurra said. “You have the same functionality; you can take the signal you want and output it anywhere within that [wide stare] range.”
Virtually all electronic defense systems require signal processing. The first requirement of these systems is to convert the signals from analog to digital to enable processing and often that is then converted back to analog after processing. In recent years interest has grown in signals higher in the RF spectrum, creating challenges for data conversion as well as the processing engines that are needed. In this video, Bob Sgandurra, Director of Product Management at Mercury Systems, discusses the advancements in Direct RF data converters, system requirements and design engineering.