Spread spectrum receiver with multi-path correction

• US 6,198,765 B1
• Filed: 09/12/1997
• Issued: 03/06/2001
• Est. Priority Date: 04/25/1996
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: SiRF Technology (Qualcomm, Inc.)
• Inventors: Kohli, Sanjai, Cahn, Charles R., Chansarkar, Mangesh
• Primary Examiner(s): Le, Amanda T.
• Assistant Examiner(s): Ha, Dac V.
• Application Number:
  US08/929,366
• Time in Patent Office: 1,271 Days
• Field of Search: 375/200, 375/202, 375/208, 375/209, 375/210, 370/335, 370/350
• US Class Current: 375/142
• CPC Class Codes: G01C 21/26 specially adapted for navigation in a road network
• CPC Class Codes: G01C 22/00 Measuring distance traversed on the ground by vehicles, persons, animals or other moving solid bodies, e.g. using odometers, using pedometers
• CPC Class Codes: G01S 19/11 wherein the cooperating elements are pseudolites or satellite radio beacon positioning system signal repeaters
• CPC Class Codes: G01S 19/22 Multipath-related issues
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/30 code related G01S19/246 takes precedence
• CPC Class Codes: G01S 19/37 Hardware or software details of the signal processing chain
• CPC Class Codes: G01S 19/47 the supplementary measurement being an inertial measurement, e.g. tightly coupled inertial
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 1/7115 Constructive combining of multi-path signals, i.e. RAKE receivers
• CPC Class Codes: H04B 2001/70706 using a code tracking loop, e.g. a delay locked loop

Abstract

A spread spectrum receiver uses a comparison of the magnitude of the code correlation amplitudes at equal power at a one chip spacing to the magnitude at a central position there between to determine if multipath interference is present. The lead or lag error from constructive or destructive multipath interference may also be determined. Inaccuracies due to such interference may then be corrected or minimized by, for example, determining the residual code phase error and/or the prompt or accurate code phase delay.

Claims

1. A spread spectrum receiver, comprising:

means for correlating a received, code modulated spread spectrum signal with a code modulated signal replica at a first, a second, and a third selected code phase delay;

comparison means for comparing characteristics of said correlations to derive information related to any residual code phase error in said second code phase delay; and

error means for determining the existence of residual code phase lead or lag error comprising means for determining the existence of multipath interference in said received, code modulated spread spectrum signal causing a residual code phase lag error if the magnitude of the correlation product at the second selected code phase delay is less than twice the magnitude of the correlation product at the first selected code phase delay.

2. A spread spectrum receiver, comprising:

means for correlating a received code modulated spread spectrum signal with a code modulated signal replica at a first, a second, and a third selected code phase delay;

comparison means for comparing characteristics of said correlations to derive information related to any residual code phase error in said second code phase delay; and

error means for determining the existence of residual code phase lead or lag error comprising means for determining the existence of multipath interference in said received, code modulated spread spectrum signal causing a residual code phase lead error if the magnitude of the correlation product at the second selected code phase delay is more than twice the magnitude of the correlation product at the first selected code phase delay.

3. A spread spectrum receiver, comprising:

means for correlating a received, code modulated spread spectrum signal with a code modulated signal replica at a first, a second, and a third selected code phase delay;

comparison means for comparing characteristics of said correlations to derive information related to any residual code phase error in said second code phase delay comprising means for selecting a prompt phase delay between said first and second code phase delays if the magnitude of the correlation product at the second selected code phase delay is less than twice the magnitude of the correlation product at the first selected code phase delay.

4. A spread spectrum receiver, comprising:

means for correlating a received, code modulated spread spectrum signal with a code modulated signal replica at a first, a second, and a third selected code phase delay;

comparison means for comparing characteristics of said correlations to derive information related to any residual code phase error in said second code phase delay comprising means for selecting a prompt phase delay at a correlation product peak between said first and second code phase delays if the magnitude of the correlation product at the second selected code phase delay is less than twice the magnitude of the correlation product at the first selected code phase delay.

5. A spread spectrum receiver, comprising:

means for correlating a received, code modulated spread spectrum signal with a code modulated signal replica at a first, a second, and a third selected code phase delay;

comparison means for comparing characteristics of said correlations to derive information related to any residual code phase error in said second code phase delay comprising means for selecting a prompt phase delay between said second and third code phase delays if the magnitude of the correlation product at the second selected code phase delay is more than twice the magnitude of the correlation product at the first selected code phase delay.

6. A spread spectrum receiver, comprising:

means for correlating a received, code modulated spread spectrum signal with a code modulated signal replica at a first, a second, and a third selected code phase delay;

comparison means for comparing characteristics of said correlations to derive information related to any residual code phase error in said second code phase delay comprising means for selecting a prompt phase delay at a peak between said second and third code phase delays if the magnitude of the correlation product at the second selected code phase delay is more than twice the magnitude of the correlation product at the first selected code phase delay.

7. A spread spectrum receiver, comprising:

means for correlating a received, code modulated spread spectrum signal with a code modulated signal replica at a first, a second, and a third selected code phase delay;

comparison means for comparing characteristics of said correlations to derive information related to any residual code phase error in said second code phase delay comprising means for selecting a prompt phase delay at said second code phase delay if the magnitude of the correlation product at the second selected code phase delay is substantially equal to the magnitude of the correlation product at the first selected code phase delay.

8. A spread spectrum receiver, comprising:

means for correlating a received, code modulated spread spectrum signal with a code modulated signal replica at a first, a second, and a third selected code phase delay;

comparison means for comparing characteristics of said correlations to derive information related to any residual code phase error in said second code phase delay; and

means responsive to the comparison means for adjusting the code phase delay of a prompt correlation.

9. A method of processing coded, spread spectrum signals with potential multipath interference, comprising the steps of:

generating a local replica of the code;

correlating the local replica with coded, spread spectrum signals as received at a first pair of code phase delays separated by a predetermined phase delay difference;

determining a second pair of code delays separated by a predetermined phase delay the magnitudes of the correlations at said second pair of code delays having a predetermined relationship, and wherein said first and second pair of code delays include a common code delay said first pair of code phase delays are separated by a code chip width, and said second pair of code phase delays are separated by one half of a code chip width; and

determining a prompt code phase delay from differences in magnitude between at least two of said correlations.

10. A method of processing coded, spread spectrum signals with potential multipath interference, comprising the steps of:

generating a local replica of the code;

correlating the local replica with coded, spread spectrum signals as received at a first pair of code phase delays separated by a predetermined phase delay difference, wherein one of the first pair of code phase delays is selected by determining a second pair of code phase delays, separated by a single code chip width, producing equal correlation magnitudes above a threshold value; and

determining a prompt code phase delay from differences in magnitude between at least two of said correlations.

11. The method of claim 10, further comprising the step of:

selecting the other of the first pair of code phase delays to be equidistant between said second pair of code phase delays.

12. The method of claim 11, wherein the comparison step further comprises the step of:

determining the presence of multipath interference from the ratio of correlation product magnitudes at said first pair of code phase delays.

13. The method of claim 12, wherein the step of determining the presence of multipath interference further comprises the step of:

determining the presence of multipath interference if the ratio of correlation product magnitudes at said first pair of code phase delays is substantially different than two.

14. The method of claim 12, further comprising the step of:

adjusting one of the first pair of phase delays to be the prompt code phase delay in response to the difference between the ratio of the correlation products and two.