System and method for acoustic Doppler velocity processing with a phased array transducer including applying correction factors to velocities orthogonal to the transducer face

1. A method of measuring velocity in a fluid medium utilizing a phased array transducer, the phased array transducer comprising a plurality of transducer elements arranged to form a single two-dimensional array, the method comprising:

receiving echoes of a plurality of beams generated by the transducer;

calculating raw velocity estimates based at least in part on the echoes; and

removing substantially a bias related to a first velocity from the raw velocity estimates, the first velocity being orthogonal to the face of the two-dimensional array.

2. The method of claim 1 , wherein the bias comprises a bias related to sound speed in a fluid medium.

3. The method of claim 1 , wherein the bias comprises a bias independent of Doppler effect.

4. The method of claim 1 , where the measured velocity is the velocity of currents in a fluid medium.

5. The method of claim 1 , where the measured velocity is the velocity of a vehicle or vessel relative to the bottom or surface of the fluid medium.

6. The method of claim 1 , where the measured velocity is the velocity of a target.

7. The method of claim 1 , wherein the removing further comprises:

determining one or more correction factors based at least in part on sound speed and/or a centroid frequency shift of one or more of the echoes; and

correcting the raw velocity estimates based on the one or more correction factors.

8. The method of claim 1 , wherein the calculating of raw velocity estimates further comprises:

calculating the autocorrelation function of the echo of each beam; and

extrapolating the phase of the autocorrelation function to a pre-determined lag for each beam.

9. A signal processing circuit adapted for incorporation in a device configured to measure velocity, the signal processing circuit being configured to perform the method of claim 1 .

10. A system configured to measure velocity, comprising:

a phased array transducer comprising a plurality of transducer elements arranged to form a single two-dimensional array, the transducer being configured to generate a plurality of beams and to receive echoes of the beams; and

a processing module configured to calculate raw velocity estimates based at least in part on the echoes and to remove substantially a bias related to a first velocity from the raw velocity estimates, the first velocity being orthogonal to the face of the two-dimensional array.

11. A system configured to measure velocity, comprising:

means for generating a plurality of beams and receive echoes of the beams, wherein the means comprises a phased array transducer, the phased array transducer comprising a plurality of transducer elements arranged to form a single two-dimensional array; and

means for calculating raw velocity estimates based at least in part on the echoes; and

means for removing substantially a bias related to a first velocity from the raw velocity estimates, the first velocity being orthogonal to the face of the two-dimensional array.

12. The method of claim 1 , wherein the removing of substantially a bias related to a first velocity from the raw velocity estimates comprises subtracting a correction term proportional to the first velocity from each of the raw velocity estimates.

13. The method of claim 12 , wherein the correction term for at least one raw velocity estimate is different from the correction term for another raw velocity estimate.

14. The system of claim 10 , wherein the processing module is configured to subtract a correction term proportional to the first velocity from each of the raw velocity estimates.

15. The system of claim 14 , wherein the correction term for at least one raw velocity estimate is different from the correction term for another raw velocity estimate.