WRIGHT-PATTERSON AFB, Ohio, 31 July 2012. Signals intelligence (SIGINT) experts at the U.S. Intelligence Advanced Research Projects Activity (IARPA) in Washington are enlisting the help of two U.S. defense companies to develop technologies to detect and pinpoint high-frequency (HF) radar and communications systems anywhere in the world.
The companies -- Systems & Technology Research LLC in Winchester, Mass., and the Northrop Grumman Corp. Information Systems segment in Chantilly Va. -- are developing antennas and signal processing to locate radar and communications systems that rely on HF signals, which is particularly difficult to do.
The companies are part of the IARPA High Frequency Geolocation and Characterization (HFGeo) Advanced HF Signal Processing program. Systems & Technology Research won a $1.5 million contract last April, and Northrop Grumman Information Systems on a $3 million contract earlier this month.
Awarding the contracts on behalf of IARPA were officials of the U.S. Air Force Research Laboratory (AFRL) at Wright-Patterson Air Force Base, Ohio. IARPA is the research arm of the Office of the Director of National Intelligence in Washington.
Many RF signals, such as VHF and UHF, are relatively easy to locate because they travel only in straight lines, and cannot easily penetrate barriers such as tall buildings and mountain ranges. HF radio signals behave in a more complex manner and are much more difficult to locate.
HF radio waves not only follow line-of-sight paths, but they also bounce off of layers Earth's upper atmosphere called the ionosphere and come back to the Earth's surface where antennas tuned to HF frequencies -- roughly 2 to 30 MHz -- can pick them up.
HF signals are particularly prone to interference because antennas literally can receive their signals from different directions and at different times because of the ionospheric bounce phenomenon. The ionosphere is ionized by solar radiation and helps propagate HF radio signals to distant locations, hence the long distances that shortwave and Ham HF radio signals can travel.
The IARPA HFGeo program seeks to geolocate and characterize HF emissions accurately. Ionospheric variation,high noise levels, and ionospheric polarization rotation, multipath induced signal fading, and simultaneous multiple angles-of-arrival will make this job challenging for sensors and signal processing experts at Systems & Technology Research Northrop Grumman Information Systems.
IARPA officials are asking engineers at the two companies to capitalize on advances in high-dynamic-range receivers, antenna techniques, adaptive signal processing, ionospheric ray path prediction, and improved measurement and modeling techniques to geolocate HF emitters around the world, as well as determine if these signals are involved with benign commercial activity, or are part of hostile communications and radar systems.
The goals of the IARPA HFGeo program include developing the ability to resolve several angles-of-arrival and polarization states accurately through novel antenna concepts; enhance signal-to-noise ratio and signal detection with multi-dimensional adaptive signal processing; determine the state of the ionosphere accurately; and integrate these technologies into geolocation and source characterization applications.
While Systems & Technology Research Northrop Grumman Information Systems are concentrating on the first two thrusts of the HFGeo program -- novel antenna concepts and signal processing algorithms -- IARPA is moving on to the next phase of the program, which involves advanced ionospheric modeling.
IARPA HFGeo Program Manager Frank Robey briefed industry on the next ionospheric modeling phase of the HFGeo program on 13 July. Briefing slides are available online at www.iarpa.gov/HFGeo_Presentations/120727_Phase1B_Proposers_Day_Part1.pdf.
A formal solicitation for the next phase of the HFGeo program should be released soon.