Acquisition of Pseudonoise Signals by Sequential Estimation

A new method of acquisition of pseudonoise signals is described. This method is based on sequential estimation of the present state of an incoming pseudonoise signal by examining a small number of input bits. Performance of the sequential estimation system is compared with the stepping correlation system, and significant improvement of acquisition time is shown for signal-to-noise ratios down to approximately -15 dB. The system also automatically gives shorter acquisition times for improved signal-to-noise ratios. Experimental results are included which verify the analytical results. In particular an average acquisition time of 74 ms is demonstrated for a -10 dB signal-to-noise ratio using a pseudonoise signal suitable for high accuracy range measurement to 3300 km unambiguous range.