DARPA HERMES program seeks to defeat RF jamming and interference with low-power wideband signals

July 16, 2014
ARLINGTON, Va., 16 July 2014. U.S. military researchers are trying to find ways to use wideband low-power RF signals to mitigate the effects of RF jamming and interference that threaten to disrupt important military operations.
ARLINGTON, Va., 16 July 2014. U.S. military researchers are trying to find ways to use wideband low-power RF and microwave signals to mitigate the effects of RF jamming and interference that threaten to disrupt important military operations.

Officials of the U.S. Defense Advanced Research Projects Agency (DARPA) in Arlington, Va., have released a solicitation to industry (DARPA-BAA-14-34) for the Hyper-wideband Enabled RF Messaging (HERMES) program to ensure reliable radio communications.

The HERMES program seeks develop advanced microsystems and techniques for jam-resistant radio frequency (RF) communications that enable wide instantaneous-bandwidth waveforms, large coding gains, and adaptive filtering to operate through jamming and interference.

To do this, researchers seek to keep the transmitted power spectral density of the RF signal to a minimum as a way to mitigate signal fratricide while assuring communications in congested RF environments.

Related: Air Force tells industry to prepare for upcoming RF and electro-optical research program

Assured access to the RF portion of the electromagnetic spectrum is critical to communications, radar sensing, command and control, time transfer, and geo-location, DARPA officials say. Radio frequencies have the unique combination of all-weather penetration and low atmospheric absorption for long distance links.

Nevertheless, access to radio frequencies can be easily denied, and the root of this problem lies in economics, officials say. The last 20 years have seen growth in demand for voice and data access for cell phones, tablet computers, and other mobile devices. As a result, more frequency bands have been reallocated to commercial use, which reduces and fragments the RF spectrum available to the military.

Only 1.4 percent of the RF spectrum from 0 to 300 GHz is available exclusively to the U.S. government, and forcing the military and other government agencies to use such a small slice of the spectrum can result in signal fratricide -- or government radio transmissions interfering with one another.

Malicious jamming also is a growing problem. It's relatively easy for adversaries to target such a small part of the RF spectrum allocated exclusively to the government.

Related: Advanced microelectronics research back in style for photonic and RF integrated circuits

What this means is that researchers need to develop RF data technologies to reclaim this lost bandwidth without unintentionally jamming others. DARPA officials intend to do this by exploring extremely wideband RF links in the HERMES program.

By using wideband signals in the presence of narrow-band jamming and interference, the idea is that wideband transmissions will enable an acceptable amount of signal to get through for voice and data communications.

Interference can be mitigated through coding gain using techniques such as direct sequence spread spectrum, DARPA officials say. Wideband operation can provide a significant coding gain while also providing useful data-rates.

In addition, The fundamental physics of high-power amplifiers tends to stifle attempts at delivering high power jamming signals with large fractional bandwidth. The receiver can reject in-band spectrum as wide as 1 GHz while still receiving 90 percent of the signal. This enables good data-rates while maintaining ultra-low power spectral densities to mitigate interference with conventional narrow-band systems.

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The goal of the HERMES program is to develop a spread-spectrum link with 10 GHz of instantaneous bandwidth with coding gain greater than 40 decibels and the ability to reject large blocks of spectrum at the receiver with minimal impact to signal integrity. Between these two effects, the objective is to achieve greater than 70 dB of jammer suppression.

There are two technical areas of interest: system architecture development, and photonic receiver development. DARPA will pursue these areas at the same time over an 18 month period. Several awards are expected, and companies selected will share about $4.5 million, DARPA officials say.

Companies interested should submit proposals no later than 13 Aug. 2014. Email questions or concerns to the HERMES program manager, Joshua Conway, at [email protected].

More information is online at https://www.fbo.gov/spg/ODA/DARPA/CMO/DARPA-BAA-14-34/listing.html.

About the Author

John Keller | Editor

John Keller is editor-in-chief of Military & Aerospace Electronics magazine, which provides extensive coverage and analysis of enabling electronic and optoelectronic technologies in military, space, and commercial aviation applications. A member of the Military & Aerospace Electronics staff since the magazine's founding in 1989, Mr. Keller took over as chief editor in 1995.

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