Rapid Acquisition of P(Y) Code Signals Using Electro-Optic Signal Processing

Modern GPS receivers adopt a digital architecture to facilitate signal processingusing high speed VHDL electronics. NAVSYS has developed a buffered digital receiver architecture (the TIDGET (TM) -PLUS) that optimizes the GPS search and acquisition process by operating in the frequency domain. The Rapid Acquisition FFT (RAFFT) approach was developed by NAVSYS initially to speed high dynamic C/A code acquisition. This technique has since been extended, under a US Navy contract, to be applied to direct P/Y code acquisition.The effectiveness of the NAVSYS RAFFT algorithm is dictated by the speed of the FFT implementation. High speed DSPs can perform a 1024 point FFTs in less than 128 usecs. The performance of the RAFFT approach can be dramatically improved by using an electro-optic correlator. Digital Spatial Light Modulators (SLM) are under development that can perform 1000x1000 2-dimensional correlations at kHz rates, which is equivalent to over 10 to the 6th parallel correlators. Under this SBIR effort an EO-RAFFT design and demonstration system will be developed and tested to demonstrate the massive parallelism possible using modern electro-optic correlation techniques. Under Phase II, a miniaturized P/Y code electro-optic correlator will be developed using Smart Pixel Array (SPA) technology suitable for integration with a GPS receiver.