An Adaptive Sonobuoy Location System Using Precision Time and Frequency Navy SBIR FY2010.1 Sol No.: Navy SBIR FY2010.1 Topic No.: N101-025 Topic Title: An Adaptive Sonobuoy Location System Using Precision Time and Frequency Proposal No.: N101-025-1578 Firm: Propagation Research Associates 1275 Kennestone Circle Suite 100 Marietta, Georgia 30066-6032 Contact: E. Holder Phone: (678) 384-3402 Web Site: http://pra-corp.com/ Abstract: Propagation Research Associates, Inc., teamed with Ultra Electronics UnderSea Sensor Systems Inc., with support from Boeing Integrated Defense Systems proposes to design and assess the performance of a Sonobuoy Location System (SLS) that implements the latest digital synchronization technology to align uplink and downlink signals. Current digital synchronizer technology will allow the PRA SLS to detect and measure low Doppler signatures that will be expected from the relative velocities between the patrol aircraft and the deployed sonobuoys. This digital technology will allow PRA to modify waveforms to adapt system performance based on operational sensitivity requirements. PRA will design and evaluate two SLS concepts - one that uses a two-way downlink/uplink and a combination of range/Doppler measurements made on the aircraft, and another that uses a one-way downlink and a combination of time-difference-of-arrival/frequency-difference-of-arrival measurements made on the sonobuoy and communicated to the patrol aircraft on existing communication channels. The objectives of this effort are to achieve required sonobuoy track accuracies while operating at any altitude, utilize as much of the existing SLS hardware and infrastructure as possible, minimize the impact of new hardware on the existing system, mitigate the effect of radio frequency interference and 5) maintain a cost effective solution. Benefits: The U.S, Navy has always been interested in improving the position estimates of deployed sonobuoys for enhanced sonar direction finding. The successful completion of Phase I will result in a design for a Sonobuoy Location System that uses the latest digital synchronization technology for accurate frequency and time-of-arrival measurements. The technology will establish coherence over remotely located transmit and receive sources that will permit the measurement of low Doppler signatures. PRA will analyze two approaches - one that uses an RF downlink-only where measurements are made on the sonobuoy and another that uses an RF downlink-uplink system where measurements are made on the aircraft. Combining Doppler with time-of-arrival measurements on an aircraft that is flying a nearly straight leg, PRA will determine the sonobuoy position and track the motion of the sonobuoy. PRA will demonstrate the performance of the two PRA SLS approaches using a simulation developed in Phase I that incorporates realistic error models. PRA will implement waveforms that have sufficient interference rejection to operate in a radio frequency interference (RFI) environment. PRA will use a family of phase coded waveforms that have low cross-correlation performance. As such one potential benefit will be the application of the PRA waveforms to other radar and communications applications where RFI is a concern. In Phase II, PRA proposes to build and demonstrate one of the two SLS approaches. PRA will use test sonobuoys provided by Ultra-USSI instrumented with GPS and a PRA transponder and will use aircraft instrumented with Inertial Navigation System. PRA will locate the transmitter/receiver/processor on the aircraft and demonstrate SLS performance with multiple flights of the aircraft. While the dominant use of this technology is necessarily restricted to military purposes, PRA can foresee several applications for component technologies that can be developed further into independent products. For example, the high speed digital processing and coherent mutistatic signal processing can be used in the communications industry to exploit spatial diversity and smart antennas to improve channel throughput (i.e., MIMO). Any technologies that require remote signal synchronization will benefit for this effort. The proposed techniques can be applied to other frequency regimes such as multistatic radar, medical imaging array applications, and the automobile industry to measure Doppler and range of adjacent objects. Return