Gps receiver with fast acquisition time

Abstract

Method for acquiring a plurality of GPS signals, in which the signals received from the space vehicles are correlated, in an array of parallel processing modules ( 20 ) with local replicas of a pseudorandom code. The local pseudorandom code generators are slewed periodically, on detection of an external periodical trigger INT_ACC, and the correlation data are dumped simultaneously to all processing modules in output registers for acquisition and tracking software. The integration period is shorter than the natural period of the pseudorandom code sequence, and all the local generators are slewed at the same time, thereby allowing a quicker acquisition of the SV C/A code.

1 . Signal processor for use in a navigation satellite receiver, comprising a plurality of tracking modules, for processing a plurality of navigation ranging signals, each tracking module comprising:
 a pseudorandom code generator, for generating a replica code sequence;   a correlator, for obtaining a time-integrated correlation value between a navigation ranging signal and said replica code sequence;   
       wherein said signal processor has a first functioning mode, and said signal processor is arranged to simultaneously dump said time-integrated correlation values from said multiplicity of tracking modules when in said first functioning mode. 
     
     
         2 . The signal processor of  claim 1 , wherein said signal processor has a second functioning mode, and said signal processor is arranged to independently dump said time-integrated correlation values from said multiplicity of tracking modules, upon completion of a period of said replica code sequence, when in said second functioning mode. 
     
     
         3 . The signal processor of  claim 1 , wherein said simultaneous dump of said time-integrated correlation values takes place on detection of an interrupt signal. 
     
     
         4 . Signal processor according to  claim 1 , wherein said tracking modules are arranged to repeatedly temporally shift said replica code sequences until said replica code sequences are aligned with pseudorandom sequences contained in said navigation ranging signals. 
     
     
         5 . The signal processor of  claim 1 , wherein said tracking modules comprise means to inhibit said temporal shift after completion of a period of said replica code sequence. 
     
     
         6 . The signal processor of  claim 1 , wherein said signal processor is arranged to monitor said time-integrated correlation values and to maintain an alignment condition between said replica code sequences and said pseudorandom sequences contained in said navigation ranging signals, by selectively temporally shifting said replica code sequences. 
     
     
         7 . The signal processor of  claim 1 , operatively arranged for selectively activating said first functioning mode at device start-up. 
     
     
         8 . The signal processor of  claim 1 , operatively arranged for selectively activating said first functioning mode when the strength of said navigation ranging signals exceeds a predefined value. 
     
     
         9 . The signal processor of  claim 1 , wherein said pseudorandom sequences are GPS C/A ranging codes. 
     
     
         10 . GPS receiver, comprising the signal processor of  claim 1 . 
     
     
         11 . Method for acquiring a plurality of navigation ranging signals from a plurality of space vehicles comprising the steps of:
 correlating said navigation ranging signals with one of a plurality of local signals generated by a plurality of pseudorandom code generators, for obtaining a plurality of time-integrated correlation values;   slewing said pseudorandom code generators until said local signals are time-aligned with pseudorandom signals contained in said navigation ranging signals;   whereas said slewing of said pseudorandom code generators takes place simultaneously and periodically for all said code generators, with a repetition period which is shorter than the proper period of said local signals.