A method of processing a digital signal derived from an analog input signal of a GNSS receiver, a GNSS receiver base band circuit for carrying out the method and a GNSS receiver

摘要

An acquisition unit of a GNSS receiver base band circuit comprises a correlator (45) with a correlator shift register (47) through which a correlation sequence derived from a characteristic basic sequence of a satellite is being fed. At every step, sum and difference of two consecutive digital values from a data sequence derived from an analog input signal are formed in parallel in adders (50; 51) of an evaluation unit (49a;b). Four evaluation sums resulting from leaving the results unchanged and multiplying them by -1 in multipliers (52, 53) are fed to correlator cells (48a;b) in parallel. Depending on the two binary values of the correlation sequence the two digital values are to be processed with, the one of the four evaluation sums which corresponds to the sum of products of the said binary values and the digital values is selected and passed on as a contribution value by an arbitration unit of the correlator cell (48a;b) where AND-connections of the binary values and their inverses are formed in parallel. The contribution value is added to a sum of previous contribution values. In this way two consecutive pairs consisting each of a digital value of the data sequence and a binary value of the correlation sequence can be processed in a single step whereby the time required for the correlation process is cut in half.