Signal select in underground line location

• US 9,473,203 B2
• Filed: 04/30/2013
• Issued: 10/18/2016
• Est. Priority Date: 04/30/2012
• Status: Active Grant

• Current Assignee: Metrotech Corporation (L'Air Liquide SA)
• Original Assignee: Metrotech Corporation (L'Air Liquide SA)
• Inventors: Petherick, Stephen John, Mainescu, George, Dracea, Ion, Stefanoiu, Razvan Gabriel, Royle, John Mark
• Primary Examiner(s): Washburn, Daniel
• Assistant Examiner(s): Hassan, Sarah
• Application Number:
  US13/874,312
• Publication Number:
  US 20130287125A1
• Time in Patent Office: 1,267 Days
• Field of Search: 375/316, 330/254
• US Class Current: 1/1
• 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, comprising:

at least one direct digital synthesizer, the direct digital synthesizer producing a composite output signal in response to an input square wave signal, the composite output signal having a first frequency component for a first period followed by a second frequency component for a second period; and

a feedback loop providing a feedback signal coupled with the at least one direct digital synthesizer that adjusts the first and second frequency components of the composite output signal;

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 and a second digital synthesizer that provides a sine wave output for generation of the input square wave signal and signals for generating a current phase signal from the feedback signal.

2. The transmitter of claim 1, wherein the current phase signal is mixed with a dispersion offset signal and integrated to form the control phase signal.

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

4. The transmitter of claim 1, wherein an operator can request a fixed current at a defined carrier frequency through a user interface coupled to the feedback loop.

5. The transmitter of claim 1, wherein the first frequency component is f0*50/51 and the second frequency component is f0*50/49, wherein f0 is a carrier frequency.

6. The transmitter of claim 5, wherein the composite output signal has 8 cycles at each of the first frequency component and the second frequency component.

7. A transmitter, comprising:

a signal generation module that generates a composite output signal, the composite output signal having a first frequency component for a first period followed by a second frequency component for a second period, the signal generation module including;

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

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

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

an output stage, the output stage coupling the composite 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.

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

a pulse-wave modulation generator that receives the composite 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 signal that provides the feedback signal to the microprocessor based on a quadrature detector signal from the quadrature detector.

10. A method, comprising:

providing, by a first direct digital synthesizer, a composite output signal based on a control phase signal and an input square wave, the composite output signal including a first frequency component for a first period followed by a second frequency component for a second period;

providing, by a second direct digital synthesizer, a sine wave output for generation of the input square wave and for generation of a current phase signal from a feedback signal; and

providing, by a feedback loop coupled to the first direct digital synthesizer and the second direct digital synthesizer, a feedback signal that adjusts the first frequency component and second frequency component of the composite output signal.

11. The method of claim 10, further comprising mixing the current phase signal with a dispersion offset signal and integrating to form the control phase signal.

12. The method of claim 10, further comprising amplifying the composite output signal and providing it to a load conductor.

13. The method of claim 10, wherein providing the feedback signal by the feedback loop comprises:

providing, by the first direct digital synthesizer, the composite output signal to an output stage, the output stage providing a first intermediary feedback signal to a measurement circuitry;

providing, by the measurement circuitry, a second intermediary feedback signal to a microprocessor; and

generating, by the microprocessor, the feedback signal in response to the second intermediary feedback signal.

14. The method of claim 10, further comprising:

providing the composite output signal to a pulse-wave modulation generator;

modulating the composite output signal, by the pulse-wave modulation generator, and providing a modulated output signal to a digital filter; and

filtering, by the digital filter, the modulated output signal, and providing a filtered output signal.