Direct P(Y)-code acquisition under a jamming environment

Direct acquisition of the GPS P(Y)-code is desirable to military users as it has a higher tolerance to jamming and spoofing when compared to the C/A-code. Until now, direct P(Y)-code acquisition was difficult as user time sources did not provide adequate accuracy, resulting in large time errors and hence lengthy code searches. Advances in user time transfer, time maintenance using stable, low power time sources, and the use of massively parallel correlator technology have made it possible to directly acquire the P(Y)-code. However, difficulties still exist as small time errors can lead to large code search spaces. By implementing a two-dimensional search using massively parallel correlator technology, searching 32000 time-frequency bins in parallel, the STS Y-EXPRESS receiver can directly acquire the P(Y)-code in a short time. This paper analyzes the problems encountered with massively parallel correlator technology for practical implementations. Data has been collected using simulations of the Y-EXPRESS signal processor for benign applications and extrapolated for acquisition at J/S values in excess of 50 dB. Analysis of this data shows both the benefits and limitations of massively parallel correlator technology and the practical feasibility of two-dimensional searches. Current receiver specifications being targeted are acquisition with a probability of 0.90 given an initial time-error of ±1 millisecond, frequency error of ±0.2 ppm, and J/S in excess of 50 dB in the 20.46 MHz signal bandwidth