SOSA approach’s impact on electronic warfare solutions
StoryOctober 10, 2024
Ian Beavers
Analog Devices
The Sensor Open Systems Architecture, or SOSA, Technical Standard has made deployment of new electronic warfare (EW) solutions faster and more modular now that a standardized chassis hardware framework has been established. No longer will the entire EW system need to be captive to a single supplier. The latest technology can now be released into the field without the need for new program specifications. EW integrators and their suppliers can focus on their specific area of expertise among the major system component blocks: radio-frequency (RF) front end, digital processing, and algorithms. Platform re-use can be accomplished with one or more of these three major components upgraded to a new solution. Integrators can now provide focused refresh upgrades in a more timely fashion based on the advancements in just one of these areas, without waiting for a revision through an entirely new program.
As the Sensor Open Systems Architecture, or SOSA approach, moves development away from a dedicated approach for a targeted electronic warfare (EW) or communications system, its modular approach enables updates of piecewise sections. Under this approach, open system architectures enable for repurposing for new use cases, while fixed radio configurations for radio-frequency (RF) bandwidths and postprocessing can now process different bands. For example, a system upgrade can now change the RF front-end module and keep the other incumbent hardware in place. Another example: A system that supported only a fixed observable X-band can now be fitted for a wide 2-GHz to 18-GHz observation, along with digital filtering and frequency-hopping to stare at selectable swaths up to 4 GHz of bandwidth.
With only an RF front-end modification, an entirely new system capability can be achieved with only partial discrete changes. Integrators can also add incremental secondary feature sets like low-latency loopback paths, fractional sample-rate precision, and linear signal correction as part of the RF updates. The SOSA approach now enables EW providers to innovate at the speed of silicon advancements in incremental fashion with rapid deployments to the field.
Before: New requirements called for new systems
Historically, the specifics of an RF system would need a new system if new requirements emerged. A heterodyne architecture for an X-band radio would require fixed band filtering and amplifiers, a defined local oscillator, and dedicated processing within an 8-GHz to 12-GHz spectrum. When an updated requirement for a more agile EW system observing 2 GHz to 18 Ghz is established, this legacy system would need to be replaced in its entirety, as it would not be flexible enough to support other wider frequency bands.
Targeted upgrades of technology were not easily accomplished, as the in-place system components could not be swapped with another vendor’s using different instruction sets, connectors, and standards. This situation created unwanted complexity for field teams that wanted to adapt or upgrade their intelligence, as the ability to adapt components would have provided faster operational readiness to defend against evolving threats.
SOSA approach enables easier updates
As the SOSA approach enables modular hardware plug-in card profiles (PICPs), let’s modify this example: Instead of requiring a new full system of RF front end, digital processing, and algorithms, only the RF section needs to be replaced. Moreover, this update can be performed in the field without sending the original unit back to its manufacturing location. A 3U VPX module supporting a wideband 2-GHz to 18-GHz radio can be used as the upgrade impetus for the new solution. A wideband direct-RF software-defined radio (SDR) could enable even more flexibility as an alternate solution for the 3U VPX module to change RF configurations.
An SDR solution further enables full configurability for unique custom frequency bands of interest across a wide 2-GHz to 18-GHz range. A programmable filter within the RF signal chain allows for custom on-the-fly updates, while digital downconversion (DDC) in the digital domain provides further targeted filtering of noise. By targeting smaller bandwidths with digital filtering of wideband noise, the dynamic range is expanded approximately +6dB for each reduction in the bandwidth by a multiple of 4. A configurable SDR in the field realizes channel, dynamic range, and instantaneous-bandwidth performance tradeoff options that might not have been possible with legacy closed systems. (Figure 1.)
[Figure 1 ǀ Configurable 3U VPX SDRs enables more flexibility when compared to legacy closed systems.]
By leveraging a companion numerically controlled oscillator (NCO) within the DDC block, an effective digital local oscillator (LO) provides further sampling power. The NCO enables tuning of the decimated bandwidth to the specific frequency of interest using precise frequency-tuning words, while multiple banks of preset filter coefficients allow for fast frequency hopping (FFH) between observable bandwidths. Rapidly changing NCO tuning words essentially permits observable bandwidths on demand. Digital-to-analog converter (DAC) transmit paths use the inverse digital up-conversion method, respectively, to achieve the same effect. Observation of multiple bands simultaneously within the SDR can be achieved using DDC filtering and NCO tuning. (Figure 2.)
[Figure 2 ǀ The observation of multiple bands within a wideband SDR using DDCs and NCO tuning.]
The OpenVPX (VITA 65) and VPX (VITA 46) standards are fundamental to the technical success of both the U.S. Army’s Modular Open Radio Frequency Architecture (MORA) and the SOSA approach. The VITA standards provide a high-performance computing architecture that can handle the demanding data-processing requirements of modern EW systems. The switched-fabric architecture of VPX also enables data transfer at higher rates and wider scalability when compared to incumbent bus-based systems of the past. This common framework is imperative for processing the large quantities of data generated in real time by EW RF sensors and their respective algorithms.
A module that conforms to the MORA 2.4 compliance standard – defined for SDR, tuner, and radiohead payloads – will be compatible in a VPX chassis. MORA creates a standard for the controlling aspects of the VPX RF payloads like bandwidth, gain, and frequency; without it, each piece of hardware would have a unique identifying aspect that would require custom hardware configuration.
With MORA compliant modules, the new SDR hardware can conveniently be controlled through a standard instruction set, as standardization enables rapid RF payload integration. System upgrades are also streamlined as new technology becomes available for installation. Deployment of many similar upgraded systems enables a common proliferation of instructions to field teams.
At the speed of progress
The slow-update limitations of legacy closed EW systems appear to be fading. The SOSA Technical Standard and MORA framework enable faster technology updates at the speed of progress, rather than at the slow rate of closed-system programs. These approaches enable new pathways of flexible RF front-end changes for EW systems of the future. A wideband direct-RF SDR offers several alternate RF processing solutions for the 3U VPX module to change RF configurations. Practically, real-world modules such as the ADSY1100 carry a wideband multichannel RF digitizer in a 3U VPX SOSA aligned format, featuring DAC sample rates up to 28 GS/sec and analog-to-digital (ADC) sample rates up to 20 GS/sec. RF personality cards customize the signal path observations. With the help of standardization through the SOSA approach, MORA, and other compliance efforts, new EW capabilities will be able to catapult defense systems into the next generation.
Ian Beavers is a Field Applications Engineer and Customer Labs manager for the Aerospace and Defense Systems team at Analog Devices in Durham, North Carolina. He has worked for the company since 1996 and has more than 30 years of experience in the semiconductor industry. Ian earned a bachelor’s degree in electrical engineering from North Carolina State University and an MBA from the University of North Carolina at Greensboro. Readers may reach the author at [email protected].
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