New Weapons in Battle To Dominate Spectrum

August 1, 2017
By Marc Couture


Next-generation receiver technology provides greater coverage and real-time data analysis.


Recent breakthroughs in multichannel signal analysis deliver a significant boost in electromagnetic spectrum coverage for airborne electronic warfare and intelligence, surveillance and reconnaissance applications. These advances make an impossible dream a reality: a cost-effective, open standards approach enabling coverage of far greater swaths of the electromagnetic spectrum, combined with the ability to analyze and act upon data in real time.

Improved radio-frequency tuner and embedded multicore supercomputing processor designs greatly increase the channel density, signal fidelity and electromagnetic spectrum (EMS) bandwidth coverage that a deployable airborne subsystem can support. Even better, these results can be realized with size-, weight- and power-optimized, open standards-based, commercial off-the-shelf hardware. The benefit for warfighters is new, unprecedented capability in the electronic warfare (EW) and intelligence, surveillance and reconnaissance (ISR) arenas, especially within communications intelligence (COMINT) and electronic intelligence (ELINT). This capability substantially upgrades the deployment of technology for persistent, accurate surveillance and the detection of signals of interest.

Historically, the number of radio-frequency channels that could be integrated into an ISR and EW payload, based on legacy Versa Module Eurocard (VME) standard module and backplane-based systems, was limited to one or two channels per six-unit slot. Another limitation typical of older system architectures was the method of exploiting the resulting EMS data. The captured signal data had to be physically backhauled to a human for post-mission analysis, introducing costly delays between data accumulation and decision making.

Newer solutions address these shortcomings. For example, the Vesper family of multichannel wideband receivers from Maryland-based DRS Signal Solutions provides greatly expanded EMS coverage and channel count, supporting up to nine channels in a single six-unit VPX slot instead of two channels. VPX is the newer, higher-performance switched fabric architecture developed by industry to replace aging VME technology. These newer Vesper receivers are available in cost-effective three-unit and six-unit VPX modules.

When coupled with processing modules based on the latest supercomputing-class multicore Intel Xeon processors, the signals intelligence (SIGINT) data flowing from these receivers can generate real-time actionable intelligence. The quality of the intelligence is much richer, going far beyond just identifying a signal of interest. The new technology enables warfighters to determine whether a target is benign or a threat requiring a response, and it identifies the target’s location in both space and time.

In the not-so-distant past, superheterodyne radio-frequency tuners designed for SIGINT, specifically COMINT and ELINT applications, only were available in six-unit VME and three-unit CompactPCI form factors. Limited to one or two channels, a six-unit VME card only covered a frequency range of 20 megahertz (MHz) to 3 gigahertz (GHz). The cards’ intermediate frequency outputs were analog, with a maximum of 40 MHz of instantaneous bandwidth. Digitization, which was performed in an analog-to-digital converter with associated processing, would occupy another separate card slot, further increasing system size and decreasing overall performance. After digitization of the analog intermediate frequency, data would be handed off to single board computers or digital signal processors for signal identification, geolocation and additional information extraction.

Single board processors usually would house one processor with a single computing core, while digital signal systems could have as many as four processors. Operating systems were often proprietary real-time software platforms. Proprietary or even custom digital protocols and transport media provided control and methods to digitize intermediate frequency and process data. The tuners required at least a full-size chassis to provide the channels needed to cover a minimum number of target emitters over a limited portion of the spectrum.

In the months since these open standard receivers were introduced, the advantages and potential they deliver for SIGINT and ELINT applications have only become more apparent. New modules based on the Vesper receivers can support up to 10 channels per card, and their intermediate frequency outputs are more than doubled to 100 MHz of instantaneous bandwidth. This improved performance brings warfighters much closer to the goal of immediate coverage over as much of the spectrum as possible, and for as long as possible. The DRS Signal Solutions Vesper SI-9173 is a six-unit OpenVPX tuner with eight to 10 channels per slot that maintains the same performance levels of narrowband systems. This results in four to five times the capacity of previous solutions while more than doubling the intermediate frequency instantaneous bandwidth (100 MHz). A transmit channel also can be realized within the same tuner adjacent to the receive channels.

Finally, the Vesper family enables high channel count interferometry and time difference of arrival (TDOA) applications and techniques. For applications where physical payload constraints call for three-unit OpenVPX, the three-unit Vesper achieves up to five channels per slot, 100 MHz intermediate frequency, instantaneous bandwidth and local oscillator distribution of up to four slots. The 3 rack-unit (U) Vesper is configurable with up to four receive channels and an optional transmit channel.

In addition to the greatly improved channel densities and bandwidth, digitization and associated processing are accomplished within the single-slot Vesper tuner itself. The high-bit resolution, analog-to-digital converters sample the analog intermediate frequency from multiple channels and feed it into a large Xilinx field-programmable gate array (for example, Virtex-7 690T), where digital down conversion or other digital signal-processing functions can occur. The Texas Instruments KeyStone II digital signal system on a chip, included with the Vesper, can further aid in signal identification and even perform demodulation. Packetized in the VITA 49 virtual radio transport standards-based format, intermediate frequency and baseband streams can exit the tuner over 10 gigabit (Gb) Ethernet.

A comparable quantum leap has occurred within digital signal processor modules. The Curtiss-Wright CHAMP-XD2 OpenVPX board delivers more than 28 times improvement in compute performance compared with older boards. Memory capacity also has grown from 2 gigabytes (GB) of double data rate (DDR) memory on an older VME board to 64 GB of DDR4 on the newer VPX design.

Big performance benefits also result from the new modules’ support for contemporary 10 Gb Ethernet data rates. Because the radio-frequency receivers support the VITA 49 protocol, a whole new level of flexibility is achieved. For example, using advanced multicast Ethernet modes, one tuner channel can send its results to a subset of Xeon D cores, or the data from multiple tuner channels can be aggregated to a single Xeon core.

This approach—enabling omnipresent spectrum coverage and extreme flexibility—can support a powerful “all-to-all architecture” based on open standard switched Ethernet that forwards data from any of many channels to any of many processor cores. Using open architecture, commercial hardware also lowers costs and speeds up the deployment of these systems. With all-to-all connectivity, any tuner channel can communicate with a Xeon core. This significantly improves the ability of a SIGINT or an ELINT system to correlate radio-frequency emitters in 3-D time and space and results in a magnitude of improvement in density.

An optimal all-to-all architecture that maximizes a full six-unit OpenVPX chassis could use sensors that can forward data from any radio-frequency channel to any processor core. Alternatively, and in unison, data can be routed to recorders for post-mission analysis. A VPX Ethernet switch routes packets to any subset of endpoints via a multicast transmission. An all-to-all architecture can allow complete interconnectivity between as many as 54 receive channels and 144 Intel Xeon D processing cores, all in a single OpenVPX chassis.

Given this hyperinterconnectivity, complex data flow and 144 Intel Xeon cores across 12 Xeon D processors, the software infrastructure and development environment is particularly critical. Curtiss-Wright employs its OpenHPEC Accelerator Suite, which leverages elite tools developed for the commercial supercomputing world and inserts them into high-performance embedded computing applications. Standard middleware, such as Message Passing Interface, can be optimized through profiling and benchmarking using the latest visualization techniques.

For today’s warfighter, EMS dominance could not be more front and center. Technological strides have broken barriers in radio-frequency channel count, signal fidelity, bandwidth coverage, processing-core count and flexibility of fabric interconnect—a networking switch or head unit linked to components. Even better, these advances have been achieved within the confines of existing size- weight- and power-constrained payload envelopes. An ever-evolving theatre of war will demand that omnipresent EMS coverage and extreme flexibility remain on the radar for developers.

 

Marc Couture is the senior product manager for Intel, PowerPC and GPGPU-based digital signal processors in the ISR Solutions group at Curtiss-Wright Defense Solutions.

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