N093-201 TITLE: Band Limited Pulse Encoding and Signal Classification

TECHNOLOGY AREAS: Ground/Sea Vehicles, Sensors, Weapons

ACQUISITION PROGRAM: PMS404 ACAT III

The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), which controls the export and import of defense-related material and services. Offerors must disclose any proposed use of foreign nationals, their country of origin, and what tasks each would accomplish in the statement of work in accordance with section 3.5.b.(7) of the solicitation.

OBJECTIVE: Development of innovative approaches for band-limited undersea pulse encoding and echo signal classification.

DESCRIPTION: Undersea weapons typically employ active sonar for target localization. In active sonar, a high-energy pulse is transmitted into the ocean medium, the pulse travels to and bounces off of targets and clutter (ocean surface and bottom, schools of fish, etc.), and the echo is later received by the underwater weapon. Round-trip signal travel time provides an estimate of target range and arrays of sensors on the weapon provide an estimate of target direction. Decoys may intercept these transmitted signals, estimate their characteristics (frequency, pulse shape, etc.) and create a fake echo which may fool the weapon into prosecuting this false echo in lieu of a true target. This SBIR topic seeks innovative schemes for pulse coding which might enable undersea weapons to better classify false echoes as false echoes.

Typical RADAR systems may employ very wide-bandwidth (spread-spectrum) techniques for pulse encoding, or wide-bandwidth phase encoding (pseudo-random noise (PRN) signals) however, these bandwidths are not well-supported by the ocean medium and typical sonar hardware. Sonar system bandwidths of approximately one to two octaves in the near-audio regime are typical in many applications (15-60 kiloHertz). The challenge is to develop effective pulse encoding technologies utilizing this limited spectral band.

Of course, as sonar systems mature, so do decoys. False echo generation systems may employ sophisticated Digital Radio Frequency Memory (DRFM) to accurately capture copies of incoming signals for subsequent re-transmission, and may also amplify and Doppler shift these false echoes to produce convincing, loud false echoes from an apparently fast-moving target that may confound a sonar's ability to locate a comparatively weak echo from a true target.

PHASE I: Development of candidate approaches for effective signal coding and signal classification using a given representative set of transmitter and receiver capabilities (sound pressure level, receive sensitivity, radiation and reception patterns, spectral bandwidth, amplitude envelope control, phase control, pulse duration, etc.). Conduct research and development (R&D) to develop potential innovative analytical theories and approaches. These investigations should identify the strengths (such as relative performance benefits) and weaknesses (such as implementation challenges) of candidate approaches and also identify the preferred approach(es) for Phase II.

PHASE II: Further develop the most promising innovative approaches identified in Phase I to demonstrate, using simulations and in-water data, where available, prototype algorithms for effective signal coding and echo classification (candidate methods may be simulated and evaluated using common programming languages (C, C++) and analysis tools (Matlab®)). Develop measures of effectiveness (MOE) to be evaluated in Phase III and identify any Government-supplied hardware required for Phase III demonstration. Participate in the spiral development process for undersea weapons (a phased process for concept development and evaluation).

PHASE III: Develop test plans and demonstrate the effectiveness of the pulse coding and signal classification approach(es) in an undersea environment using representative weapon hardware (transmitter, sensor, receiver) and undersea echo repeaters. Analyze in-water data and compare performance with existing approaches. Continue to participate in the spiral development process for undersea weapons.

PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Sonar signal classification technologies to better discriminate true sonar contacts from intentionally created false echoes. These technologies might be used for a Port Security applications where large numbers of false decoys may be created to mask a true interloper.

REFERENCES:
1. Goj, Walter W., "Synthetic Aperture RADAR and Electronic Warfare," Artech House, Boston, 1993.

2. Vakin, Sergei A., et. al. "Fundamentals of Electronic Warfare," Artech House, Boston, 2001.

3. Adamy, David A., "EW 101," Artech House, Boston, 2001.

4. Waite, A D, "SONAR for Practising [sic] Engineers," John Wiley & Sons Ltd., 2002.

5. Roome, S. "Digital Radio Frequency Memory," IEE Electronics and Communications Engineering Journal, (August 1990), pp. 147-53.

6. DeFilippo, et al., "Simulator for advaced fighter EPM development," IEE Proc. Radar Radar, Sonar and Navigation, vol. 148, no 3, (June 2001), pp. 139-46.

KEYWORDS: signal processing; classification; waveforms; encryption; undersea weapons; countermeasures

** TOPIC AUTHOR (TPOC) **

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