Method For Detection Of Signal Source Using Estimation Of Noise Statistics

• US 20090278542A1
• Filed: 04/04/2007
• Published: 11/12/2009
• Est. Priority Date: 04/04/2006
• Status: Active Grant

• Current Assignee: Charles Machine Works Incorporated The
• Original Assignee: Charles Machine Works Incorporated The
• Inventors: Gard, Michael F., Cole, Scott Bryan
• Granted Patent: US 7,999,551 B2
• Time in Patent Office: Days
• US Class Current: 324/334
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat

Abstract

A method for noise signal analysis and communication with an underground transmitter. The method comprises the steps of measuring a noise floor when no signal is transmitted from a transmitter, detecting a signal when the transmitter is transmitting, and estimating the noise free component of the signal by removing the noise floor measurement. The measurement of the noise floor and detecting the signal from the transmitter may be done using a root mean square technique. The noise floor measurement can be removed from the measured signal by subtracting the noise floor measurement from the measured signal or alternatively by calculating the square root of the difference between the square of the measured signal and the square of the noise floor measurement. The noise estimation technique may be used in connection with, a differential phased shift keying communication scheme or other modulation techniques.

Claims

1. A method for analyzing signals transmitted from a below ground transmitter, the method comprising the steps of:

obtaining a noise measurement at an above ground location when no signal is transmitted from a below ground transmitter, the noise measurement having a magnitude;

transmitting an electromagnetic signal from the transmitter;

detecting the electromagnetic signal at the above ground location, the detected signal having a magnitude with a noise free component; and

estimating the noise free component of the detected signal by removing the noise measurement magnitude from the detected signal magnitude.

2. The method of claim 1 wherein the step of obtaining a noise measurement comprises the steps of:

measuring a detected electromagnetic field by taking measurement samples during a period of time; and

calculating the root mean square of the measured field samples.

3. The method of claim 1 wherein the step of detecting the electromagnetic signal comprises the steps of:

measuring a detected electromagnetic field transmitted by the transmitter by taking measurement samples during a period of time; and

calculating the root mean square of the measured field samples.

4. The system of claim 1 further comprising the step of calculating a depth of the transmitter using the noise free component of the signal.

5. The system of claim 1 further comprising the step of determining a location of the transmitter using the noise free component of the signal.

6. The system of claim 1 further comprising the step of calculating flux angles using the noise free component of the signal.

7. The method of claim 1 wherein the step of estimating a noise free component comprises the step of calculating the square root of the difference between the square of the detected signal magnitude and the square of the noise measurement magnitude.

8. The system of claim 7 further comprising the step of calculating a depth of the transmitter using the estimated noise free component of the electromagnetic signal.

9. The method of claim 1 wherein the step of estimating a noise free component comprises the step of calculating the difference between the detected signal magnitude and the noise measurement magnitude.

10. The system of claim 9 further comprising the step of calculating a depth of the transmitter using the noise free component of the electromagnetic signal.

11. The method of claim 1 further comprising the step of modulating information representing an operational parameter of the transmitter onto the signal transmitted from the transmitter.

12. The method of claim 11 wherein the step of modulating information onto the signal comprises a phase shift keying communication scheme.

13. The method of claim 12 wherein the step of modulating information onto the signal further comprises a communication protocol, the communication protocol identifying a period of time in which the transmitter is turned off.

14. The method of claim 11 wherein the operational parameter comprises roll.

15. The method of claim 11 wherein the operational parameter comprises battery level.

16. A method for analyzing signals transmitted from a below ground transmitter, the method comprising the steps of:

obtaining a noise measurement at an above ground location when no signal is transmitted from a below ground transmitter, the noise measurement having a magnitude;

transmitting an electromagnetic signal from the transmitter;

modulating information representing an operational parameter of the transmitter onto the electromagnetic signal;

detecting the electromagnetic signal at the above ground location, the detected signal having a magnitude and a noise free component;

estimating the noise free component of the detected signal by removing the noise measurement magnitude from the detected signal magnitude; and

determining a location of the transmitter, a depth of the transmitter, or flux angles using the noise free component of the signal.

17. The method of claim 16 wherein the operational parameter comprises roll.

18. The method of claim 16 further comprising the step of calculating a depth of the transmitter using the noise free component of the electromagnetic signal.

19. The method of claim 16 wherein the step of modulating information onto the signal comprises a differential phase shift keying communication scheme.