Method and apparatus for improved L2 performance in dual frequency semi-codeless GPS receivers

Abstract

This invention relates to improving the signal-to-noise ratio of semi-codeless tracking by presenting a method and apparatus which employs an optimal W-code timing pattern, and/or provides signal-to-noise gain by adding L1 and L2 W-code bit timing estimate signals before combining the L1 W-code estimate signal with the L2 W-code estimate signal.

1 - 16 . (canceled)  
   
   
       17 : An apparatus for tracking remotely generated signals comprising: 
 a first tracker for tracking a first component of a first remotely generated signal and including a W-code signal generator responsive to a second component of the first signal for locally generating a first W-code signal from a second component of the first signal; and    a second tracker for tracking a first component of a second remotely generated signal according to the first W-code signal; wherein    the second component of the first signal has the same pattern as the first component of the second signal.    
   
   
       18 : An apparatus according to  claim 17 , wherein the pattern comprises: 
 a known pattern combined with an unknown pattern.    
   
   
       19 : An apparatus according to  claim 18 , wherein timing information about the unknown pattern is known.  
   
   
       20 : An apparatus for tracking remotely generated signals comprising: 
 a first tracker for tracking a first component of a first remotely generated signal and including a W-code signal generator responsive to a second component of the first signal for locally generating a first W-code signal from a second component of the first signal; and    a second tracker for tracking a first component of a second remotely generated signal according to the first W-code signal; wherein    the second component of the first signal has the same pattern as the first component of the second signal;    the pattern comprises a known pattern combined with an unknown pattern;    timing information about the unknown pattern is known; and    the first tracker generates a timing signal in accordance with the timing information for improving the accuracy of the first W-code signal.    
   
   
       21 : An apparatus for tracking signals comprising: 
 a first tracker for tracking a first component of a first signal and for generating a first estimate signal from a second component of the first signal; and    a second tracker for tracking a first component of a second signal according to the first estimate signal; wherein    the second component of the first signal has the same pattern as the first component of the second signal;    the pattern comprises a known pattern combined with an unknown pattern;    the first signal is a GPS LI signal;    the second signal is a GPS L2 signal;    the first component of the GPS LI signal is a C/A-code component;    the second component of the GPS LI signal is a Y-code component;    the first component of the GPS L2-signal is a Y-code component;    the known pattern is a GPS P-code;    the unknown pattern is a GPS W-code.    
   
   
       22 : An apparatus according to  claim 21 , wherein the W-code has a plurality of bit edges, further comprising means for determining the precise location in time of each of said bit edges.