Signal correlation technique for a receiver of a spread spectrum signal including a pseudo-random noise code that reduces errors when a multipath signal is present

• US 6,272,189 B1
• Filed: 02/01/1999
• Issued: 08/07/2001
• Est. Priority Date: 09/25/1996
• Status: Expired due to Term

• Current Assignee: MiTAC International Corporation (MiTAC Holdings Corp.)
• Original Assignee: Magellan Corporation (Thales SA)
• Inventors: Kamgar, Farbod, Garin, Lionel, Zhodzicshsky, Mark, Veitsel, Victor, Sila-Novatisky, Stanislov
• Primary Examiner(s): Bocure, Tesfaldet
• Application Number:
  US09/241,797
• Time in Patent Office: 918 Days
• Field of Search: 375/208, 375/316, 375/326, 375/267, 375/347, 375/343, 455/132, 455/137, 325/149, 325/150, 325/147
• US Class Current: 375/343
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop

Abstract

A receiver of a radio frequency signal having a pseudo-random noise (PRN) code modulated on a carrier, and techniques of processing such a signal that are especially adapted for ranging applications. Such an application is in a global positioning system (GPS or GLONASS) receiver. Both of the receiver DLL code and PLL carrier loops include a loop component that senses an error in its main loop caused by the presence of a multipath signal. The main loop is continuously adjusted by this sensed error, thereby causing the loop to track more precisely and minimize the effect of the multipath signal. The result is a more accurate range measurement.

Claims

1. A method of processing a received signal that includes line-of-sight and multipath versions of a transmitted signal, comprising:

locally generating a signal that corresponds to a component of the received signal,

correlating the locally generated signal with the received signal,

using a result of the correlation to adjust a phase of the locally generated signal relative to a phase of the received signal component,

independently of the correlating step, determining an amount of error in the correlation that has occurred as a result of the multipath signal being present in the received signal, and

using the determined error to further adjust the phase of the locally generated signal relative to the phase of the received signal component in order to minimize the determined error, thereby substantially reducing the effect of the multipath version of the received-signal.

2. The method according to claim 1 wherein said component of the received signal is a pseudo-random noise binary code.

3. The method according to claim 1 wherein said component of the received signal is a carrier.

4. A method of decoding an incoming signal containing a carrier having encoded thereon a pseudo-random noise (PRN) binary code, comprising:

locally generating first and second gating signals that relate to the PRN code of the incoming signal, said first and second gating signals having different shapes, wherein one of said first and second gating signals is shaped symmetrically about an edge of the PRN binary code in the incoming signal, and the other of said first and second gating signals is shaped asymmetrically about an edge of the PRN binary code in the incoming signal,

mixing the incoming signal with the first locally generated gating signal, thereby to generate a first mixed signal,

mixing the incoming signal with the second locally generated gating signal, thereby to generate a second mixed signal,

combining the first and second mixed signals, thereby to generate an error signal, and

adjusting together a phase of the first and second locally generated gating signals relative to that of the PRN binary code of the incoming signal in order to drive said error signal to a reference.