TECHNOLOGY AREAS: Sensors, Electronics, Battlespace

ACQUISITION PROGRAM: Radio Frequency Antennas & Topside Program Manager, code PMW 180-D4/E2

OBJECTIVE: Develop methods usable in real-time to generate multi-bit reference templates for initially unidentified signals to allow them to be more accurately identified and searched for in subsequent signals.

DESCRIPTION: Cross-correlation is an especially effective method for doing digital matched filtering in wideband systems in complex signal environments. Doing this filtering by using matching of a table of

20 parameters that describe the signals' external characteristics is becoming increasingly ineffective as frequency and waveform agile transmitters become the norm. More information is required. Fortunately, the maturation of high speed digital technologies allows this correlation process to begin while the signal is still represented at the carrier frequency and doing so harvests additional processing gain not available if the signals are reduced to the base-band information before beginning. Because correlation involves mixing, it is very desirable that the reference templates contain little noise, be it of environmental, system, or quantization origin. Thus the templates should contain more bits than the quantized representation of the current signal. Moreover, in the most desirable wide band, software defined systems, the reference template must potentially have the same band width as the widest band signal expected, tho more normally it will be narrower. In principle, templates for known signals may be stored in a large, rapidly read-out memory, waiting for recall and utilization. However, in practice, channel distortions such as multi-path effects may alter the details of the perfect template. Moreover, not all signals are known a priori and for uncooperative sources, the latency involved in deciding which templates to invoke may be unacceptable in real-time systems. Thus it is desirable to develop a technique for defining new templates as the signals are first encountered, storing them in an indexed fashion, and making them available to functional cross-correlators in both the current and future moments.

PHASE I: Analyze cooperative communications signals in the HF, UHF, S, X, and Ka bands and determine the range of template lengths and word widths that it is desirable to implement. Design a hardware realization of a system to create the templates and calculate the cross-correlation of these templates with an ADC representation of a complex total waveform composed of more than 10 in-band signals having different modulation and arising from incoherent transmitters. The ideal hardware should not be limited to operation in a single band or for a specific modulation class, but instead be generic. Proposals should indicate the kinds of digital technologies that would be considered for the receiver system.

PHASE II: Implement and demonstrate the designed hardware chain operating on two or more simultaneous cooperative communications signals and yielding an increased effective signal to noise ratio of the system. Develop concepts for the modifications required to address non-cooperative signal sources.

PHASE III: Such units will find application in both communications and ISR systems. In particular, comms systems will be able to trade off lower bit error rate, lower transmit power, and smaller receive arrays.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: The same hardware could be used in settings where the signal is badly corrupted by multipath such as wireless and UWB comms in urban environments. Indeed, by making the template longer and more accurate, the functionality of few tap rake receivers may be exceeded, simplifying the system architecture.

REFERENCES:
1. http://www.patentstorm.us/patents/5661527-description.html

2. http://209.85.165.104/search?q=cache:xX7JWkGo3mQJ:www.isis.vanderbilt.edu/publications/archive/ Chhokra_K_5_0_2004_WASP__A_Ra.pdf+temporal+cross-correlation+templates,+RF+matched+filter&hl=en&ct=clnk&cd=6&gl=us

3. http://www.freepatentsonline.com/7099367.html

KEYWORDS: cross-correlation; matched filtering; digital reception; templates; digital signal processing; high speed processing

TPOC: Deborah VanVechten
Phone: (703)696-4219
Fax: (703)696-8496
Email: [email protected]
2nd TPOC: Anna Leese de Escobar
Phone: (619)553-5987
Fax: (619)553-1090
Email: [email protected]
3rd TPOC: Holly Lane
Phone:
Fax:
Email: [email protected]

** TOPIC AUTHOR (TPOC) **

DoD Notice:   Between November 13 and December 9, 2007, you may talk directly with the Topic Author(s) to ask technical questions about the topics. Their contact information is listed above. For reasons of competitive fairness, direct communication between proposers and topic authors is not allowed starting December 10, 2007, when DoD begins accepting proposals for this solicitation.

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