Patent ID: 8175137
Filing Date: 2012-05-08
Classification: G01S,H04B

Abstract:
1. A method of processing a digital signal derived from a direct-sequence spread spectrum analog signal containing at least one encoded binary sequence consisting of repetitions of a characteristic basic sequence which extends over a basic interval, the method comprising the following consecutive steps: deriving from the digital signal a plurality of data sequences each consisting of a series of data values, correlating each data sequence with a plurality of copies of a correlation sequence derived from the basic sequence, the copies having different phase positions with respect to the data sequences, by in each case sequentially multiplying the data values each with a value of the correlation sequence and adding up the products to form a correlation value corresponding to a phase position and a data sequence, evaluating for each phase position the correlation values established with the plurality of data sequences, where in each case the phase position of the correlation sequence with respect to the data sequence corresponds to the respective phase position, together in order to determine a correlation indicator corresponding to said phase position, where the evaluation involves for each phase position: for each of the plurality of data sequences comparing the correlation value to at least a first value threshold and a second value threshold which is greater than the first value threshold and assigning to an integer correlation term a first value if the correlation value is below the first value threshold, a second value which is greater than the first value if the correlation value is equal to or greater than the second value threshold and a value greater than the second value otherwise, contributing to an integer correlation counter corresponding to the respective phase position by sequentially adding the correlation terms corresponding to said phase position and to one of the plurality of data sequences, determining the correlation indicator corresponding to the respective phase position where the determination involves the correlation counter corresponding to said phase position in such a way that the partial ordering of the correlation indicators with respect to magnitude corresponds to the partial ordering of the correlation counters with respect to magnitude.