Radio receiver for determining location of a signal source

1. A method for determining an accurate location of a signal's source of transmission, comprising:

demodulating, by a receiver of a communication device, a detected carrier signal modulated with a Pseudo Noise (“PN”) code sequence to obtain an original information-bearing signal therefrom;

computing, by the receiver, time delay offsets using correlations of PN code windows for each symbol of the original information-bearing signal;

curve fitting the time delay offsets to construct a fitted curve that has a best fit to a series of data points defining the time delay offsets;

extrapolating unknown time delay offsets using the fitted curve;

determining, by the receiver, a high accuracy Time Of Arrival (“TOA”) of the detected carrier signal using at least one of the time delay offsets and the unknown time delay offsets; and

using, by the receiver, the high accuracy TOA to determine an accurate location of the original information-bearing signal's source of transmission.

2. The method according to claim 1 , wherein the demodulating comprises:

detecting a phase deviation from the detected carrier signal;

removing the phase deviation from the detected carrier signal;

performing early/late gate tracking to recover symbol timing phase of the detected carrier signal; and

performing demodulation of the detected carrier signal using the recovered symbol timing thereof to extract the original information-bearing signal therefrom.

3. The method according to claim 2 , wherein the high accuracy TOA is determined using the unknown time delay offsets that were extrapolated using the fitted curve.

4. The method according to claim 1 , further comprising refining the high accuracy TOA by:

determining a satellite position;

computing an atmospheric and relativistic delay that effected the detected carrier signal during transmission thereof using the satellite position; and

applying the atmospheric and relativistic delay to the high accuracy TOA so as to generate a refined TOA.

5. The method according to claim 4 , further comprising using the refined TOA to determine an accurate location of the original information-bearing signal's source.

6. The method according to claim 1 , wherein the high accuracy TOA is determined by:

determining through signal detection, a coarse TOA and a coarse Frequency Of Arrival (“FOA”) for a sample of the original information-bearing signal;

performing a multi-stage down conversion process using at least samples associated with the coarse FOA at a point of detection to remove a Doppler effect from the original information-bearing signal;

cross correlating a first set of samples from the original information-bearing signal with the removed Doppler effect to a second set of samples from a local copy of the PN code sequence to determine a cross correlation peak;

using the cross correlation peak to find a first temporal peak center for a puke for each symbol of the original information-bearing signal;

using the first temporal peak center to obtain a set of first estimated symbols;

using the set of first estimated symbols to obtain a value representing twice a center frequency; and

down converting the first set of sample using the center frequency to remove any remaining trace of Doppler effect from the original information-bearing signal.

7. The method according to claim 6 , wherein a high resolution TOA process comprises:

obtaining a correlation peak by cross correlating a third set of samples obtained from the original information-bearing signal with a removed Doppler effect to a fourth set of samples obtained from the local copy of the PN code sequence;

using the second temporal peak center to obtain a set of second estimated symbols;

generating a curve fit using the set of second estimated symbols; and

determining the high accuracy TOA by dividing an intercept value of a sample-by-sample rate, where the intercept value is obtained using the curve fit and samples associated with the coarse TOA.

8. A system, comprising:

a receiver comprising an electronic circuit configured to:

demodulate a detected carrier signal modulated with a Pseudo Noise (“PN”) code to obtain an original information-bearing signal therefrom;

compute time delay offsets using correlations of PN code windows for each symbol of the original information-bearing signal;

curve fit the time delay offsets to construct a fitted curve that has a best fit to a series of data points defining the time delay offsets;

extrapolate unknown time delay offsets using the fitted curve;

determine a high accuracy Time Of Arrival (“TOA”) of the detected carrier signal using at least one of the time delay offsets and the unknown time delay offsets; and

use the high accuracy TOA to determine an accurate location of the original information-bearing signal's source of transmission.

9. The system according to claim 8 , wherein the demodulating comprises:

detecting a phase deviation from the detected carrier signal;

removing the phase deviation from the detected carrier signal;

performing early/late gate tracking to recover symbol timing phase of the detected carrier signal; and

performing demodulation of the detected carrier signal using the recovered symbol timing thereof to extract the original information-bearing signal therefrom.

10. The system according to claim 9 , wherein the high accuracy TOA is determined using the unknown time delay offsets that were extrapolated using the fitted curve.

11. The system according to claim 8 , wherein the high accuracy TOA is refined by: determining a satellite position:

computing an atmospheric and relativistic delay that effected the detected carrier signal during transmission thereof using the satellite position: and

applying the atmospheric and relativistic delay to the high accuracy TOA so as to generate a refined TOA.

12. The system according to claim 11 , wherein the refined TOA is used to determine an accurate location of the original information-bearing signal's source.

13. The system according to claim 8 , wherein the high accuracy TOA is determined by:

determining, through signal detection, a coarse TOA and a coarse Frequency of Arrival (“FOA”) for a sample of the original information-bearing signal;

performing a multi-stage down conversion process using at least samples associated with the coarse FOA at a point of detection to remove a Doppler effect from the original information-bearing signal;

cross correlating a first set of samples from the original information-bearing signal with the removed Doppler effect to a second set of samples from a local copy of the PN code sequence to determine a cross correlation peak;

using the cross correlation peak to find a first temporal peak center for a pulse for each symbol of the original information-bearing signal;

using the cross correlation peak to find a first temporal peak center for a pulse for each symbol of the original information-bearing signal;

using the first temporal peak center to obtain a first estimated symbols;

using the set of first estimated symbols to obtain a value representing twice a center frequency; and

down converting the first set of samples using the center frequency to remove any remaining Doppler effect from the original information-bearing signal.

14. The system according to claim 13 , wherein a high resolution TOA process comprises:

obtaining a correlation peak by cross correlating a third set of samples obtained from the original information-bearing signal with removed Doppler effect to a fourth set of samples obtained from the local copy of the PN code sequence;

using the second temporal peak center to obtain a set of second estimated generating a curve fit using the set of second estimated symbols; and

determining the high accuracy TOA by dividing an intercept value of a sample-by-sample rate, where the intercept value is obtained using the curve lit and samples associated with the coarse TOA.