×

Mitigation of multipath effects in global positioning system receivers

  • US 5,963,582 A
  • Filed: 11/21/1997
  • Issued: 10/05/1999
  • Est. Priority Date: 05/24/1996
  • Status: Expired due to Term
First Claim
Patent Images

1. In a receiver for decoding received pseudorandom noise (PRN) encoded signals, apparatus for mitigating effects of multipath signals on code tracking of the received PRN signals, the apparatus comprising:

  • a PRN code generator for generating a replica of the PRN code and for generating related code multipath mitigation windows (MMWs);

    a controllable oscillator, for generating timing signals for the PRN code generator;

    a first correlator, for correlating the received PRN signals with the replica of the PRN code, to derive phase error signals used for controlling the oscillator; and

    a second correlator, for correlating the received PRN signals with the code MMWs, and thereby generating code error signals, in accordance with a code error function, used to control the PRN code generator to synchronize the generated PRN code with the received PRN code signals;

    wherein the code error function effectively has a zero value at a desired rack point when the generated PRN code is synchronized with the received PRN signals and, immediately on each side of the tracking point, has a polarity that depends on whether the generated PRN code is early or late with respect to the received PRN code;

    and wherein the shape of the code MMWs generated by the PRN code generator is selected to provide a code error function that mitigates the effect of received multipath signals by providing an error value that increases rapidly in opposite directions from the track point, but assumes a practically zero value when the code MMWs are advanced only a fraction of a PRN code chip from the track point, whereby a code error function associated with delayed multipath code signals will have a practically zero value near the desired track point and will have little or no effect on tracking the received code signals;

    and wherein the code MMWs are narrow with respect to a PRN code chip and are timed to occur only at PRN code transitions.

View all claims
  • 0 Assignments
Timeline View
Assignment View
    ×
    ×