Pseudorandom binary sequence apparatus and method for in-line inspection tool

1. An in-line inspection tool for inspecting the wall of a pipeline while traveling through the pipeline, the in-line inspection tool comprising:

a transmitter;

a signal generator generating a pseudorandom signal, generating an inspection signal, and driving the transmitter with a convolution of the pseudorandom signal and the inspection signal;

the transmitter transmitting, in the form of a transmitted stress wave traveling primarily circumferentially, the convolution to the wall of the pipeline; and

one or more receivers detecting in the wall of the pipeline a received stress wave after the received stress wave has traveled circumferentially at least about 120 degrees within the wall of the pipeline, the one or more receivers outputting a received signal comprising at least one of the convolution and a reflection of the convolution.

2. The in-line inspection tool of claim 1 , wherein the transmitter and receiver each comprise one or more magnetostrictive electromagnetic acoustic transducers.

3. The in-line inspection tool of claim 1 , wherein the transmitter and receiver each comprise one or more Lohrentz force electromagnetic acoustic transducers.

4. The in-line inspection tool of claim 1 , wherein the transmitter and receiver each comprise an electromagnetic acoustic transducer.

5. The in-line inspection tool of claim 1 , wherein the transmitter and receiver each comprise one or more piezoelectric ultrasonic transducers.

6. The in-line inspection tool of claim 5 , wherein the one or more piezoelectric ultrasonic transducers operate at one of normal incidence and oblique incidence.

7. The in-line inspection tool of claim 5 , wherein the one or more piezoelectric ultrasonic transducers operate as a phased array.

8. The in-line inspection tool of claim 1 , further comprising a decoder identifying the inspection signal within the received signal by cross correlating the received signal and the pseudorandom signal.

9. A method comprising:

selecting an in-line inspection tool comprising a transmitter, signal generator, and one or more receivers;

inserting the in-line inspection tool within a pipeline having a wall;

generating, by the signal generator, a pseudorandom signal;

generating, by the signal generator, an inspection signal;

driving, by the signal generator, the transmitter with a convolution of the pseudorandom signal and the inspection signal;

transmitting, by the transmitter in response to the driving, the convolution to the wall of the pipeline in the form of a transmitted stress wave traveling primarily circumferentially within the wall;

receiving, by the one or more receivers, a received stress wave from the wall of the pipeline after the received stress wave has traveled at least about 360 degrees circumferentially around the pipeline;

generating, by the one or more receivers in response to the receiving, a received signal comprising at least one of the convolution and a reflection of the convolution; and

identifying the inspection signal within the received signal by cross correlating the received signal and the pseudorandom signal.

10. The method of claim 9 , wherein the transmitter and one or more receivers each comprise one or more magnetostrictive electromagnetic acoustic transducers.

11. The method of claim 9 , wherein the transmitter and one or more receivers each comprise one or more Lohrentz force electromagnetic acoustic transducers.

12. The method of claim 9 , wherein:

the transmitter and receiver each comprise one or more piezoelectric ultrasonic transducers; and

the one or more piezoelectric ultrasonic transducers operate at one of normal incidence and oblique incidence.

13. The method of claim 9 , wherein:

the transmitter and receiver each comprise one or more piezoelectric ultrasonic transducers; and

the one or more piezoelectric ultrasonic transducers operate as a phased array.

14. A method of inspecting a pipeline, the method comprising:

selecting a pipeline having a wall;

selecting an in-line inspection tool comprising a transmitter and a receiver;

traveling, by the in-line inspection tool, within the pipeline;

transmitting, by the transmitter during the traveling, a convolution of a pseudorandom signal and a inspection signal to the wall of the pipeline in the form of a transmitted stress wave traveling primarily circumferentially within the wall;

receiving, by the receiver, a received stress wave from the wall of the pipeline after the received stress wave has traveled at least about 120 degrees circumferentially around the pipeline;

generating, by the receiver in response to the receiving, a received signal comprising at least one of the convolution and a reflection of the convolution; and

identifying the inspection signal within the received signal by cross correlating the received signal and the pseudorandom signal.

15. The method of claim 14 , wherein the transmitter and receiver each comprise one or more magnetostrictive electromagnetic acoustic transducers.

16. The method of claim 14 , wherein the transmitter and receiver each comprise one or more Lohrentz force electromagnetic acoustic transducers.

17. The method of claim 14 , wherein the transmitter and receiver each comprise an electromagnetic acoustic transducer.

18. The method of claim 14 , wherein the transmitter and receiver each comprise one or more piezoelectric ultrasonic transducers.

19. The method of claim 18 , wherein the one or more piezoelectric ultrasonic transducers operate at one of normal incidence and oblique incidence.

20. The method of claim 18 , wherein the one or more piezoelectric ultrasonic transducers operate as a phased array.