Satellite signal receiver with detector of incoherence between code phase and carrier frequency measurements

• US 6,172,638 B1
• Filed: 01/15/1999
• Issued: 01/09/2001
• Est. Priority Date: 06/07/1996
• Status: Expired due to Fees

• Current Assignee: Sextant Avionique
• Original Assignee: Sextant Avionique
• Inventors: Arethens, Jean-Pierre
• Primary Examiner(s): Issing, Gregory C.
• Application Number:
  US09/147,334
• Time in Patent Office: 725 Days
• Field of Search: 342/357.02, 342/357.03, 342/357.16, 701/214
• US Class Current: 342/357.44
• CPC Class Codes: G01S 19/071 DGPS corrections
• CPC Class Codes: G01S 19/20 Integrity monitoring, fault detection or fault isolation of space segment

Abstract

A satellite signal GPS receiver which is located at a fixed station on the ground. The receivers are used in differential position measurement systems. In order to eliminate as much as possible the influence of multipaths on the precision of the measured position, it is detected whether the position measurements are coherent with the velocity measurements, The coherence is measured by the variations in the difference V_i−dPRC_i/dt, where V_i is the relative velocity measured along the axis of the i^th satellite and dPRC/dt is the time variation of the measured position. If the coherence is not sufficient, the position variation should not correspond to the measured velocity. The measurement of this satellite is then considered to be tainted with error and the satellite is eliminated. In the absence of multipaths, the above difference should be seen to vary periodically. This variation may be detected by a Fourier transform on a sufficient number of measurement samples.

Claims

1. A method for eliminating position measurement errors in a satellite positioning receiver, comprising the steps of:

measuring a relative distance and a relative velocity between the satellite positioning receiver and a respective satellite;

calculating a time variation of the relative distance;

determining a difference between the time variation and the relative velocity;

determining if the measured relative distance is coherent with the measured relative velocity based on the difference determined in the determining step;

calculating an average of successive differences determined in the determining step; and

determining variations of the average,

wherein a probable position measurement error exists if the average of successive differences varies.

2. The method according to claim 1, further comprising the steps of:

determining a variation level of the average calculated in the calculating step; and

comparing the variation level with a determined threshold.

3. The method according to claim 1, further comprising the steps of:

searching for a characteristic variation frequency of the average calculated in the calculating step; and

comparing an amplitude of variation of said characteristic variation frequency with a determined threshold.

4. A system for eliminating position measurement errors in a satellite positioning receiver, comprising:

means for measuring a relative distance and a relative velocity between the satellite positioning receiver and a respective satellite;

means for determining a time variation of the relative distance;

means for determining a difference between the time variation and the relative velocity;

means for determining if the measured relative distance is coherent with the measured relative velocity based on the difference determined by the determining means;

means for calculating an average of successive differences determined by the determining means; and

means for determining variations of the average,

wherein a probable position measurement error exists if the average of successive differences varies.

5. The system according to claim 4, further comprising:

means for determining a variation level of the average calculated by the calculating means; and

means for comparing the variation level with a determined threshold.

6. The system according to claim 4, further comprising:

means for searching for a characteristic variation frequency of the average calculated by the calculation means; and

means for comparing an amplitude of variation of said characteristic variation frequency with a determined threshold.

7. A satellite positioning receiver for eliminating position measurement errors in a satellite positioning receiver, comprising:

a measuring mechanism configured to measure a relative distance and a relative velocity between the satellite positioning receiver and a respective satellite;

a calculating unit configured to calculate a time variation of the relative distance;

a determining unit configured to determine a difference between the time variation and the relative velocity;

a determining mechanism configured to determine if the measured relative distance is coherent with the measured relative velocity based on the difference determined in the determining step;

a calculating mechanism configured to calculate an average of successive differences determined by the determining unit; and

a determining mechanism configured to determine variations of the average,

wherein a position measurement error probably exists if the average of successive differences varies.

8. The receiver according to claim 7, further comprising:

a determining mechanism configured to determine a variation level of the average calculated by the calculating mechanism; and

a comparing mechanism configured to compare the variation level with a determined threshold.

9. The receiver according to claim 7, further comprising:

a searching mechanism configured to search for a characteristic variation frequency of the average calculated by the calculating mechanism; and

a comparing mechanism configured to compare an amplitude of variation of said characteristic variation frequency with a determined threshold.