DARPA Wants to Create Jam-Resistant Comm System
This article originally appeared in TV Technology.
DARPA is soliciting for innovative research proposals to explore the feasibility of a wideband spread-spectrum RF communications system with greater than 10 GHz of instantaneous bandwidth in its Hyper-wideband Enabled RF Messaging (HERMES) effort. The communications system has to operate below 20 GHz to mitigate atmospheric absorption and must employ coding gain and spectral filtering for resistance to jamming.
Proposed studies will advance technology through “1) investigation of system architectures, channel propagation effects, spectrum regulation, signal processing techniques and culminating in a demonstration using commercial components and 2) the development of novel receiver technologies with a path towards a handheld radio size, weight and power envelope.”
The document DARPA-BAA-14-34_HERMES_Final_For_Posting_30June2014.pdf has more details on the opportunity. Explaining the need for the research, DARPA states, “Allocating small slices of the spectrum to defense allows adversaries to effectively target their efforts. As a result, we have seen the aggressive development and fielding of electronic attack technologies. The effort described herein will study means to reclaim this lost bandwidth without unintentionally jamming others.”
Here is the document’s technical description of the HERMES effort:
“In recognition of these severe and mounting challenges, DARPA is exploring extremely wideband RF links. Increasing bandwidth provides resiliency to interference through two principle modes. First and foremost, interference can be mitigated through coding gain using techniques such as direct sequence spread spectrum. Wideband operation has the potential to provide a significant coding gain while also providing operationally useful data-rates. To date, coding gains of more than 50 dB have been demonstrated but with data-rates below 100 bps. Increasing the bandwidth by a factor 1,000 will yield a commensurate increase in data-rate while maintaining the coding gain. Second, operating at over 10 GHz of spectrum with large fractional bandwidth also provides resistance to jamming through a less conventional means. The fundamental physics of high-power amplifiers tends to stifle attempts at delivering high power jamming signals with large fractional bandwidth. Physics favors resonant devices. The receiver, then, can reject in-band spectrum as wide as 1 GHz while still receiving 90% of the signal. The wideband operation also enables relevant data-rates while maintaining ultralow-power spectral densities to mitigate interference with conventional narrow-band systems.”
This sounds like an interesting project. The phrase “reclaim this lost bandwidth without unintentionally jamming others” would indicate they will be looking at the impact on other users of the spectrum. These include satellite uplinks at 6 GHz and 14 GHz, downlinks at 4 GHz and 12 GHz, numerous fixed terrestrial microwave bands, and, in the future, 5G at 15 GHz.