Method and apparatus for receiving GPS/GLONASS signals

Abstract

A method of processing received L1 and L2 spread spectrum signals is disclosed. In one embodiment, the method comprises i) locally generating replicas of a known P-code, wherein each of the received signals includes a unique frequency carrier with the known pseudo-random P-code and an unknown code modulated thereon, ii) making the code replicas available at different relative phases, iii) demodulating the received L1 and L2 signals with replicas of the P-code, iv) repetitively and separately integrating the demodulated L1 and L2 signals over time periods related to the unknown code, and v) correlating an integration result for one of the L1 and L2 signals with an integration result for the other of the L1 and L2 signals.

1 . A method of processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random code modulated thereon, each L1 and L2 signal being converted into a plurality of digital signals, the method comprising: 
 locally generating a single replica of the known code;    making the code replica available at different relative phases;    first demodulating the converted L1 and L2 signals with the single replica of the known code without any substantial delay, the first demodulated signal being associated with the L1 signal;    second demodulating the converted L1 and L2 signals with the generated replica of the known code from one of the taps of the delay line, the second demodulated signal being associated with the L2 signal;    selectably switching the converted L1 and L2 signals for the first demodulation and selectably switching the converted L1 and L2 signals for the second demodulation;    repetitively and separately integrating the demodulated L1 and L2 signals over a time period; and    adjusting the phases of the locally generated code replicas relative to the incoming L1 and L2 signals in order to maximize the power of the integrated demodulated L1 and L2 signals.    
     
     
         2 . The method according to  claim 1 , wherein the resulting locally generated code phases are useable to determine information of the location of a receiving position with high accuracy.  
     
     
         3 . The method according to  claim 1 , wherein the frequency carriers are also modulated with an unknown code and the phase adjustment includes: 
 correlating an integration result for one of the L1 and L2 signals with an integration result for the other of the L1 and L2 signals; and    adjusting the phases of the locally generated known code replicas relative to the incoming L1 and L2 signals in order to maximize the power of the correlated L1 and L2 signals, wherein the resulting locally generated known code phases are useable to determine information of the location of a receiving position.    
     
     
         4 . The method according to  claim 1 , wherein the integrating of the demodulated L1 and L2 signals comprises: 
 first integrating the demodulated signals over a first predetermined period of time; and    second integrating the first integrated signals over a second predetermined period of time longer than the first predetermined period of time.    
     
     
         5 . The method according to  claim 1 , wherein the received L1 and L2 spread spectrum signals are received from at least one of a Global Positioning System (GPS) and Global Orbiting Navigation Satellite System (GLONASS).  
     
     
         6 . An apparatus for processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random P-code and an unknown code modulated thereon, the apparatus comprising: 
 a generator of replicas of the known P-code;    a delay line configured to make the known P-code replicas available at different relative phases;    a first demodulator, connected to the generator, configured to demodulate one of the received L1 and L2 signals with one of the known P-code replicas;    a second demodulator configured to demodulate the other of the received L1 and L2 signals with one of the known P-code replicas;    a first integrator configured to repetitively and separately integrate the demodulated one of the L1 and L2 signals over time periods related to the unknown code;    a second integrator configured to repetitively and separately integrate the demodulated other of the L1 and L2 signals over time periods related to the unknown code; and    a correlator configured to correlate the first integrator output with the second integrator output.    
     
     
         7 . The apparatus according to  claim 6 , wherein the correlator includes: 
 a comparator configured to compare the absolute values of the integrated demodulated L1 and L2 signals;    a combiner configured to individually combine the values of the integrated demodulated L1 and L2 signals with a unitary value having the largest value as output by the comparator;    a first accumulator configured to individually and separately accumulate the combined values for the demodulated one of the L1 and L2 signals; and    a second accumulator configured to individually and separately accumulate the combined values for the demodulated other of the L1 and L2 signals.    
     
     
         8 . The apparatus according to  claim 7 , further comprising a phase adjuster configured to adjust the phases of the locally generated P-code replicas relative to the incoming L1 and L2 signals in order to maximize the power of the correlated L1 and L2 signals.  
     
     
         9 . The apparatus according to  claim 7 , wherein the combiner comprises a multiplier.  
     
     
         10 . The apparatus according to  claim 7 , wherein the first accumulator operates functionally as an adder and the second accumulator operates as a combiner.  
     
     
         11 . The apparatus according to  claim 6 , wherein the apparatus is for use with at least one of a Global Positioning System (GPS) and Global Orbiting Navigation Satellite System (GLONASS).  
     
     
         12 . An apparatus for processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random code modulated thereon, each L1 and L2 signal being converted into a plurality of digital signals, the apparatus comprising: 
 a generator configured to locally generate a single replica of the known code;    a delay line wherefrom the known P-code replicas are available at different relative phases thereof, wherein the single replica of the known code is applied to the delay line;    a first demodulator configured to first demodulate the converted L1 and L2 signals with the single replica of the known code without any substantial delay, the first demodulated signal being associated with the L1 signal;    a second demodulator configured to second demodulate the converted L1 and L2 signals with the generated replica of the known code from one of the taps of the delay line, the second demodulated signal being associated with the L2 signal;    a switch configured to selectably switch the converted L1 and L2 signals for the first demodulation and selectably switch the converted L1 and L2 signals for the second demodulation;    an integrator configured to repetitively and separately integrate the demodulated L1 and L2 signals over a time period; and    a phase adjuster configured to adjust the phases of the locally generated code replicas relative to the incoming L1 and L2 signals in order to maximize the power of the integrated demodulated L1 and L2 signals.    
     
     
         13 . A method of processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random P-code and an unknown code modulated thereon, the method comprising: 
 locally generating replicas of the known P-code;    making the code replicas available at different relative phases;    demodulating the received L1 and L2 signals with replicas of the P-code;    repetitively and separately integrating the demodulated L1 and L2 signals over time periods related to the unknown code; and    correlating an integration result for one of the L1 and L2 signals with an integration result for the other of the L1 and L2 signals.    
     
     
         14 . The method according to  claim 13 , further comprising adjusting the phases of the locally generated P-code replicas relative to the incoming L1 and L2 signals in order to maximize the power of the correlated L1 and L2 signals.  
     
     
         15 . The method according to  claim 14 , wherein the correlating comprises: 
 comparing the absolute values of the integrated demodulated L1 and L2 signals;    individually combining the values of the integrated demodulated L1 and L2 signals with a unitary value having the largest value as determined in the comparing; and    individually and separately accumulating the combined values.    
     
     
         16 . The method according to  claim 15 , wherein the combining comprises multiplying.  
     
     
         17 . The method according to  claim 13 , wherein the received L1 and L2 spread spectrum signals are received from at least one of a Global Positioning System (GPS) and Global Orbiting Navigation Satellite System (GLONASS).  
     
     
         18 . The method according to  claim 13 , wherein the resulting locally generated P-code phases are useable to determine information of the location of a receiving position.  
     
     
         19 . A system for processing received L1 and L2 spread spectrum signals, wherein each of the signals includes a unique frequency carrier with a known pseudo-random code modulated thereon, each L1 and L2 signal being converted into a plurality of digital signals, the system comprising: 
 means for locally generating a single replica of the known code;    means for making the code replica available at different relative phases;    means for first demodulating the converted L1 and L2 signals with the single replica of the known code without any substantial delay, the first demodulated signal being associated with the L1 signal;    means for second demodulating the converted L1 and L2 signals with the generated replica of the known code from one of the taps of the delay line, the second demodulated signal being associated with the L2 signal;    means for selectably switching the converted L1 and L2 signals for the first demodulation and selectably switching the converted L1 and L2 signals for the second demodulation;    means for repetitively and separately integrating the demodulated L1 and L2 signals over a time period; and    means for adjusting the phases of the locally generated code replicas relative to the incoming L1 and L2 signals in order to maximize the power of the integrated demodulated L1 and L2 signals.