SIGNAL SELECT IN UNDERGROUND LINE LOCATION

• US 20130287125A1
• Filed: 04/30/2013
• Published: 10/31/2013
• Est. Priority Date: 04/30/2012
• Status: Active Grant

• Current Assignee: Metrotech Corporation (L'Air Liquide SA)
• Original Assignee: Vivax-Metrotech
• Inventors: Petherick, Stephen John, Royle, John Mark, Mainescu, George, Dracea, Ion, Stefanoiu, Razvan Gabriel
• Granted Patent: US 9,473,203 B2
• Time in Patent Office: Days
• US Class Current: 375/257
• CPC Class Codes: G01S 17/10 using transmission of interrupted, pulse-modulated waves determination of distance by phase measurements G01S17/32
• CPC Class Codes: G01V 3/08 operating with magnetic or electric fields produced or modified by objects or geological structures or by detecting devices with electromagnetic waves G01V3/12
• CPC Class Codes: G01V 3/15 specially adapted for use during transport, e.g. by a person, vehicle or boat
• CPC Class Codes: H01P 5/16 Conjugate devices, i.e. devices having at least one port decoupled from one other port
• CPC Class Codes: H04B 3/04 Control of transmission; Equalising
• CPC Class Codes: H04B 3/46 Monitoring; Testing
• CPC Class Codes: H04L 27/14 Demodulator circuits; Receiver circuits

Abstract

A transmitter and receiver for performing a signal select algorithm are provided. A transmitter for providing a signal on a line to be located includes at least one direct digital synthesizer, the direct digital synthesizer producing two component frequencies in response to an input square wave signal; and a feedback loop providing the input square wave.

Claims

1. A transmitter for providing a signal on a line to be located, comprising:

at least one direct digital synthesizer, the direct digital synthesizer producing an output signal with two component frequencies in response to an input square wave signal; and

a feedback loop providing a feedback signal coupled with the at least one direct digital synthesizer that adjusts the two component frequencies.

2. The transmitter of claim 1, wherein the at least one direct digital synthesizer includes a first digital synthesizer that produces an output signal from the input square wave signal and a control phase signal.

3. The transmitter of claim 2, wherein the at least one direct digital synthesizer includes a second digital synthesizer that provides a sine wave output for generation of the input square wave and signals for generating a current phase signal from a feedback signal.

4. The transmitter of claim 3, wherein the current phase signal is mixed with a dispersion offset signal and integrated to form the control phase signal.

5. The transmitter of claim 1, further including an amplifier that couples the output signal to a load conductor.

6. A transmitter, comprising:

a signal generation module that generates an output signal having two frequencies, the signal generation module including at least one direct digital synthesizer;

an output stage, the output stage coupling the output signal to a load conductor;

a measurement circuitry that receives a signal from the output stage and phase signals from the signal generation module and providing a feedback signal; and

a microprocessor coupled to the signal generation module and the measurement circuitry, the microprocessor controlling the signal generation module in response to the feedback signal.

7. The transmitter of claim 6, wherein the at least one digital signal processor of the signal generation module includes

a first direct digital synthesizer that provides the output signal based on a control phase signal and an FSK control signal,

a second direct digital synthesizer that provides a quadrature signal based on the FSK control signal and the control phase signal, and

a third direct digital synthesizer that provides an in-phase signal based on the control phase signal and the FSK control signal.

8. The transmitter of claim 7, wherein the output stage includes

a pulse-wave modulation generator that receives the output signal from the signal generation module,

a digital filter that receives a modulated output signal from the pulse-wave modulation generator, and

an output circuit that couples a filtered output signal from the digital filter to the load conductor, the output circuit providing a signal to the measurement circuitry.

9. The transmitter of claim 8, wherein the measurement circuitry includes

a measurement amplifier coupled to receive the signal from the output circuit,

a quadrature detector coupled to receive an amplifier signal from the measurement amplifier, and

a measurement processor that provides the feedback signal to the microprocessor based on the quadrature detector signal from the quadrature detector.

10. A receiver, comprising

an antenna provides an antenna signal based on a detected signal;

an analog filter that filters the antenna signal to generate a filtered signal;

an amplifier that amplifiers the filtered signal to generate an amplified signal;

a CODEC that receives the amplified signal and provides a decoded signal; and

a digital signal processor that analyzes the decoded signal to receive a signal select signal that includes two frequencies, the digital signal processor including

a demodulator to demodulate and downsample the decoded signal to receive an in-phase component and a quadrature component; and

a calculation that provides the intensity and phase of a signal formed from the in-phase component and the quadrature component.

11. The receiver of claim 10, wherein the digital signal processor provides a phase error function based on the in-phase and quadrature components.

12. The receiver of claim 10, wherein the digital signal processor provides a phase correction based on the in-phase and quadrature components.

13. The receiver of claim 10, wherein the digital signal processor provides phase tracking.

14. A method of receiving a frequency modulated signal from an underground line, comprising:

measuring a phase of two frequency separated signals;

calculating a gradient of a phase dispersal function; and

determining an offset based on the gradient.

15. A method of receiving a signal from an underground line, comprising:

processing incoming signals from one or more antennas;

demodulating the signal select waveform;

establishing a phase reference for a transmitter phase;

accessing a difference between the phase reference and a measured phase to provide a measure of signal select.