Code multipath reduction using weighted correlation channels

• US 5,949,815 A
• Filed: 11/01/1996
• Issued: 09/07/1999
• Est. Priority Date: 11/01/1996
• Status: Expired due to Term

• Current Assignee: Trimble Navigation Limited (Trimble Inc.)
• Original Assignee: Trimble Navigation Limited (Trimble Inc.)
• Inventors: Pon, Rayman W.
• Primary Examiner(s): Vo, Don N.
• Assistant Examiner(s): Park, Albert C.
• Application Number:
  US08/742,892
• Time in Patent Office: 1,040 Days
• Field of Search: 375/209, 375/346, 375/347, 375/349, 375/285, 375/200, 375/208, 375/367
• US Class Current: 375/150
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence

Abstract

The apparatus and method for minimization the residual multipath pseudorange error signal present in the received composite spread spectrum signal are disclosed. In the preferred embodiment, the apparatus comprises at least two tracking channels. Each tracking channel includes a generator of a time-varying non-uniform weighting function. Each tracking channel processes an incoming composite signal and outputs a satellite signal and a multipath pseudorange error signal. The tracking channel output signals are scaled by the computer and combined to yield the output signal comprising a satellite signal and a minimized multipath pseudorange error signal in the area of small delays.

Claims

1. An apparatus for use in decoding a composite signal (CD) including a satellite signal from a satellite and including a multipath distortion component, said apparatus comprising:

a main tracking satellite channel circuit for tracking said composite signal from said satellite, wherein said main channel circuit processes said composite signal and generates a main satellite pseudorange estimate signal and a main multipath pseudorange error signal; and

wherein said main tracking satellite channel circuit further comprises;

a reference tracking circuit for downconverting said composite signal and for generating a reference signal; and

a main weighting correlation tracking circuit for generating a main weighting correlation signal;

wherein said main weighting correlation tracking circuit further comprises;

a main weighting function generator for generating a main weighting signal, wherein said main weighting signal is multiplied by said reference signal;

wherein said main weighting function generator further includes;

a main enabling circuit for generating non-uniform weighting function W comprising an integer number `n` of weighting values;

{W₁^m ;

W₂^m . . . W_n^m };

and

a main correlation function generator connected to said main weighting function generator for generating a main correlation signal by correlating said reference signal multiplied by said main weighting function with a locally generated replica of a satellite signal, wherein said main correlation signal includes said main multipath pseudorange error signal;

at least one additional tracking satellite channel for tracking said composite signal from said satellite, wherein each said additional channel circuit processes said composite signal and generates an additional satellite pseudorange estimate signal and an additional multipath pseudorange error signal;

and

a computer circuit connected to said main channel circuit and connected to each said additional channel circuit for assigning a main scaling function to said main channel circuit;

for assigning an additional scaling function to each said additional channel circuit;

for processing said scaled main satellite pseudorange estimate signal, said scaled main multipath pseudorange error signal, each said scaled additional satellite pseudorange estimate signal, and each said scaled additional multipath pseudorange error signal; and

for minimizing said main multipath pseudorange error signal by optimizing said main scaling function and each said additional scaling function.

2. An apparatus for use in decoding a composite signal (CD) including a satellite signal from a satellite and including a multipath distortion component, said apparatus comprising:

a main tracking satellite channel circuit for tracking said composite signal from said satellite, wherein said main channel circuit processes said composite signal and generates a main satellite pseudorange estimate signal and a main multipath pseudorange error signal;

at least one additional tracking satellite channel for tracking said composite signal from said satellite, and wherein each said additional channel circuit processes said composite signal and generates an additional satellite pseudorange estimate signal and an additional multipath pseudorange error signal;

wherein at least one said additional tracking satellite channel circuit further comprises;

an additional weighting correlation tracking circuit configured to generate an additional weighting correlation signal;

wherein each said additional weighting correlation tracking circuit further comprises;

an additional weighting function generator for generating an additional weighting signal;

wherein each said additional weighting function generator further includes;

an additional enabling circuit for generating non-uniform weighting function W comprising an integer number `k` of weighting values {W₁^a ;

W₂^a ;

. . . W_k^a };

and

an additional correlation function generator connected to said additional weighting function generator for generating an additional correlation signal by correlating said reference signal multiplied by said additional weighting function with a locally generated replica of a satellite signal, wherein said additional correlation signal includes said additional multipath pseudorange error signal;

and

a computer circuit connected to said main channel circuit and connected to each said additional channel circuit for assigning a main scaling function to said main channel circuit;

for assigning an additional scaling function to each said additional channel circuit;

for processing said scaled main satellite pseudorange estimate signal, said scaled main multipath pseudorange error signal, each said scaled additional satellite pseudorange estimate signal, and each said scaled additional multipath pseudorange error signal; and

for minimizing said main multipath pseudorange error signal by optimizing said main scaling function and each said additional scaling function.

3. A method for decoding a composite signal including a satellite signal and a multipath distortion component, said method comprising the steps of:

generating a reference signal by a main channel circuit;

generating a time varying main weighting signal by a main weighting circuit;

wherein said main weighting signal is mixed with said reference signal;

generating a main correlation signal by correlating a locally generated replica of said satellite signal with said main weighting signal mixed with said reference signal;

wherein said main correlation signal includes a main multipath pseudorange error signal;

generating at least one time varying additional weighting signal by an additional weighting circuit, wherein said additional weighting signal is mixed with said reference signal;

generating at least one additional correlation signal by correlating said locally generated replica of said satellite signal with each said additional weighting signal mixed with said reference signal;

wherein said additional correlation signal includes an additional multipath pseudorange error signal;

and

assigning a main scaling factor to said main channel circuit, assigning an additional scaling factor to each said additional channel circuit;

closing the code and carrier tracking loops for main channel;

closing the code and carrier tracking loops for each said additional channel;

processing said main correlation signal and each said additional correlation signal, and actually minimizing said main multipath pseudorange error signal by optimizing said main scaling factor and by optimizing each said additional scaling factor by using a computer.