Method for Self-Calibration of Frequency Offsets

• US 20110187594A1
• Filed: 01/26/2011
• Published: 08/04/2011
• Est. Priority Date: 02/04/2010
• Status: Active Grant

• Current Assignee: Airbus Defence and Space GmbH
• Original Assignee: Astrium GmbH (Airbus SE)
• Inventors: WENDEL, Jan
• Granted Patent: US 8,643,542 B2
• Time in Patent Office: Days
• US Class Current: 342/357.59
• CPC Class Codes: G01S 19/23 Testing, monitoring, correcting or calibrating of receiver elements
• CPC Class Codes: G01S 19/29 carrier including Doppler, related G01S19/246 takes precedence

Abstract

A method for self-calibration of frequency offsets in a measurement equipment of an interference monitoring system is provided. The method involves sampling I/Q data using the interference monitoring system measurement equipment and acquiring satellite navigation signals from the I/Q data. A carrier frequency of the satellite navigation signal is estimated and an expected carrier frequency of the satellite navigation signal is calculated. The expected carrier frequency of the satellite navigation signal is compared with the estimated carrier frequency of the satellite navigation signal and a frequency offset value is calculated as the difference between the expected and estimated carrier frequencies of the satellite navigation signal. The frequency offset value is stored in a memory and used to compensate the frequency offset of at least one subsequent measurement.

Claims

1. A method for self-calibration of frequency offsets in measurement equipment of an interference monitoring system, the method comprising the steps of:

a) sampling I/Q data using the interference monitoring system measurement equipment;

b) acquiring a satellite navigation signal from the I/Q data;

c) estimating a carrier frequency of the satellite navigation signal;

d) calculating an expected carrier frequency of the satellite navigation signal;

e) comparing the expected carrier frequency of the satellite navigation signal with the estimated carrier frequency of the satellite navigation signal and calculating a frequency offset value as the difference between the expected and estimated carrier frequencies of the satellite navigation signal;

f) storing the frequency offset value in a memory; and

g) using the stored frequency offset value to compensate the frequency offset of at least one subsequent measurement.

2. The method according to claim 1, wherein the acquisition of navigation signals in step b) is carried out by correlating the sampled I/Q data with replica signals of different code phases and carrier frequencies.

3. The method according to claim 1, wherein in the step of estimating the carrier frequency of the satellite navigation signal satellite visibility is calculated from known ephemeris or almanac data.

4. The method according to claim 1, wherein the expected carrier frequency of the satellite navigation signal is calculated from the position of an antenna of the measurement equipment, satellite position and satellite velocity.

5. The method according to claim 1, wherein the acquisition of the satellite navigation signals from the I/Q data is carried out in two sub-steps:

b1) carrying out a coarse acquisition sub-step first; and

b2) carrying out a refinement acquisition sub-step thereafter.

6. The method according to claim 5, wherein in the refinement acquisition sub-step an acquisition technique is applied with narrow frequency bins.

7. The method according to claim 5, wherein in the refinement acquisition sub-step the I/Q data sampled in step a) are processed in a tracking loop implementation initialized from results of the coarse acquisition in sub-step b1).

8. The method according to claim 1, wherein the frequency offset value is calculated at more than one frequency of interest.

9. Self-calibration device for calibrating frequency offsets in a measurement equipment of an interference monitoring system, wherein the device executes instructions stored on a non-transitory computer-readable medium causing the device to:

a) sample I/Q data using the interference monitoring system measurement equipment;

b) acquire a satellite navigation signal from the I/Q data;

c) estimate a carrier frequency of the satellite navigation signal;

d) calculate an expected carrier frequency of the satellite navigation signal;

e) compare the expected carrier frequency of the satellite navigation signal with the estimated carrier frequency of the satellite navigation signal and calculate a frequency offset value as the difference between the expected and estimated carrier frequencies of the satellite navigation signal;

f) store the frequency offset value in a memory; and

g) use the stored frequency offset value to compensate the frequency offset of at least one subsequent measurement.

10. The self-calibration device according to claim 9, wherein the acquisition of navigation signals in step b) is carried out by correlating the sampled I/Q data with replica signals of different code phases and carrier frequencies.

11. The self-calibration device according to claim 9, wherein the estimation of the carrier frequency of the satellite navigation signal satellite visibility is calculated from known ephemeris or almanac data.

12. The self-calibration device according to claim 9, wherein the expected carrier frequency of the satellite navigation signal is calculated from the position of an antenna of the measurement equipment, satellite position and satellite velocity.

13. The self-calibration device according to claim 9, wherein the acquisition of the satellite navigation signals from the I/Q data is carried out by first carrying out a coarse acquisition and subsequently carrying out a refinement acquisition.

14. The self-calibration device according to claim 13, wherein the refinement acquisition applies an acquisition technique with narrow frequency bins.

15. The self-calibration device according to claim 13, wherein in the refinement acquisition the sampled I/Q data are processed in a tracking loop implementation initialized from results of the coarse acquisition.

16. The self-calibration device according to claim 9, wherein the frequency offset value is calculated at more than one frequency of interest.

17. An interference monitoring system comprising measurement equipment provided with a self-calibrating device that executes instructions stored on a non-transitory computer-readable medium causing the device to:

a) sample I/Q data using the interference monitoring system measurement equipment;

b) acquire a satellite navigation signal from the I/Q data;

c) estimate a carrier frequency of the satellite navigation signal;

d) calculate an expected carrier frequency of the satellite navigation signal;

e) compare the expected carrier frequency of the satellite navigation signal with the estimated carrier frequency of the satellite navigation signal and calculate a frequency offset value as the difference between the expected and estimated carrier frequencies of the satellite navigation signal;

f) store the frequency offset value in a memory; and

g) use the stored frequency offset value to compensate the frequency offset of at least one subsequent measurement.