SBIR-STTR Award

In the SRGPS landing system, phase observables are uplinked to approaching aircraft where an integer ambiguity based double difference solution is computed. The probability of successful updates is sensitive to the number and quality of carrier phase observables. SRGPS must contend with rapidly changing multipath scatter and blockages from the ships structure. Antenna mounting limitations mandate multiple antenna diversity: System software must continuously select the best available signal path for each satellite. A post correlator diversity (PCD) approach has been developed for monitoring and weighting raw data prior to tracking loops by leveraging TISIs patented Integrated Demodulation/Navigation (IDN) processor. In contrast to conventional post loop diversity (PLD), this method responds before tracking loop damage can occur. PCD also offers J/S improvement. Phase biases induced by antenna lever errors are minimized by integrating ship flexure and IMU biases states. Beamformer diversity antenna elements are utilized for enhanced jamming margin and multipath rejection. Beamformer synthesis is based upon a proven military design. Integrity monitoring is provided over an independent ship-referenced path. In TISIs Phase I effort, both non-linear tracking simulations of the SRGPS shipside architecture and interfaces between TISIs PCD processor and Rockwell Collins beamformer are carried out.

Benefit:
The post correlator diversity processor applies to all precise positioning and attitude determination applications subjected to blockage and multipath. Beyond aviation, construction vehicle guidance and control as well as marine docking guidance are important. Low earth orbit attitude determination and docking in space applications would benefit. PCD also applies to cellular communication station capacity improvement.

Keywords:
Jamming, Jamming, tracking, beamforming, Multipath, aiding, SRGPS, phase, diversity

The Ship Relative GPS (SRGPS) system will support high intensity launch and recovery of fixed and rotary wing manned aircraft, as well as UAV and UCAV types, aboard a variety of ships. Critical to its success will be GPS phase tracking at high J/S levels, and detection and rejection of shipboard multipath. In Phase I TISI developed a multi-antenna architecture combining Post Correlator Diversity (PCD) and Space Time Adaptive Processing (STAP). TISI and sub-contractor Rockwell-Collins were successful in achieving A/J and multipath objectives. High fidelity simulation models of PCD signal tracking diversity functions were developed by TISI and Rockwell-Collins performed simulations of the STAP antenna system components. During Phase II a demonstration version of the combined STAP-PCD configuration will be assembled and tested. Hardware/firmware elements will be built around TISIs GPS receiver development platform and Rockwell-Collins STAP/ SAASM receivers. Testing will be carried out at the Antenna Wavefront Simulator (AWFS) facility in Dayton OH. Ten Phase II tasks are defined in the primary development period followed by a five-task option for field experiments, including ground and air unit integration with the SRGPS test bed, and support of shore-side and shipboard tests.

Benefit:
The STAPPCD system may be deployed aboard 200 or more NAVY ships. The system could be installed at a large number of shore-side military landing facilities. STAP-PCD also represents a solution to spoofing and jamming of civilian airport facilities. Lastly, in vehicle positioning and attitude-determination, PCD overcomes vehicle blockage and flexure problems.

Keywords: