Method and apparatus for digital detection of electromagnetic signal strength and signal direction in metallic pipes and cables
First Claim
1. A locator receiver, comprising:
- at least one processing channel including an electromagnetic field detector, an analog processor coupled to receive signals from the electromagnetic field detector, and a digital processor coupled to receive signals from the analog processor and calculate a signal strength parameter and a modulated signal, wherein the modulated signal is configured to provide data concerning a direction of a signal to distinguish a target conductor,wherein the digital processor includes an analog-to-digital converter, a digital phase-locked loop coupled to receive the output signal from the analog-to-digital converter and provide the signal strength parameter, and a nested digital phase-locked loop coupled to the phase-locked loop to provide the modulated signal.
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Accused Products
Abstract
A new digital architecture for metallic pipe and cable locators, providing accurate estimation of the fundamental locate parameters, electromagnetic signal strength and signal direction, and utilizing a nested Digital Phase-Locked Loop (DPLL) structure is disclosed. The obstacles to signal direction measurement in low SINR environments using the signal select method are overcome and a more precise phase comparison between the carrier and the FM modulation signals is obtained. The architecture further significantly reduces analog front-end hardware requirements, offers wider resistance to component tolerances, lower calibration and test time, and provides flexible frequency selectivity. Locators according to the present invention provide accurate estimation of the fundamental physical parameters of line location (electromagnetic signal strength and signal direction) in extremely noisy environments, using Digital Signal Processing (DSP) methods.
108 Citations
49 Claims
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1. A locator receiver, comprising:
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at least one processing channel including an electromagnetic field detector, an analog processor coupled to receive signals from the electromagnetic field detector, and a digital processor coupled to receive signals from the analog processor and calculate a signal strength parameter and a modulated signal, wherein the modulated signal is configured to provide data concerning a direction of a signal to distinguish a target conductor, wherein the digital processor includes an analog-to-digital converter, a digital phase-locked loop coupled to receive the output signal from the analog-to-digital converter and provide the signal strength parameter, and a nested digital phase-locked loop coupled to the phase-locked loop to provide the modulated signal. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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2. A locator receiver, comprising:
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at least one processing channel including an electromagnetic field detector, an analog processor coupled to receive signals from the electromagnetic field detector, and a digital processor coupled to receive signals from the analog processor and calculate a signal strength parameter and a modulated signal, wherein the digital processor includes an analog-to-digital converter, a digital phase-locked loop coupled to receive the output signal from the analog-to-digital converter and provide the signal strength parameter, and a nested digital phase-locked loop coupled to the phase-locked loop to provide the modulated signal, wherein the analog-to-digital converter operates at twice the bandwidth of a highest selectable frequency of an electromagnetic field detected by the electromagnetic field detector.
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3. A locator receiver, comprising:
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at least one processing channel including an electromagnetic field detector, an analog processor coupled to receive signals from the electromagnetic field detector, and a digital processor coupled to receive signals from the analog processor and calculate a signal strength parameter and a modulated signal; and a processor coupled to receive the signal strength parameter from each of the at least one processing channel and provide values of characteristics of a conductor based on the signal strength parameter to a display, wherein the digital processor includes an analog-to-digital converter, a digital phase-locked loop coupled to receive the output signal from the analog-to-digital converter and provide the signal strength parameter, and a nested digital phase-locked loop coupled to the phase-locked loop to provide the modulated signal. - View Dependent Claims (4, 5, 6)
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7. A locator receiver, comprising:
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at least one processing channel including an electromagnetic field detector, an analog processor coupled to receive signals from the electromagnetic field detector, and a digital processor coupled to receive signals from the analog processor and calculate a signal strength parameter and a modulated signal, wherein the digital processor includes an analog-to-digital converter, a digital phase-locked loop coupled to receive the output signal from the analog-to-digital converter and provide the signal strength parameter, and a nested digital phase-locked loop coupled to the phase-locked loop to provide the modulated signal, wherein the analog-to-digital converter operates at a sample rate of less than twice the bandwidth of a highest selectable locate frequency.
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14. A locator receiver, comprising:
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at least one processing channel including an electromagnetic field detector, an analog processor coupled to receive signals from the electromagnetic field detector, and a digital processor coupled to receive signals from the analog processor and calculate a signal strength parameter and a modulated signal, wherein the digital processor includes an analog-to-digital converter, a digital phase-locked loop coupled to receive the output signal from the analog-to-digital converter and provide the signal strength parameter, and a nested digital phase-locked loop coupled to the phase-locked loop to provide the modulated signal, wherein the digital phase-locked loop comprises; a numerically controlled oscillator coupled to receive an error signal and update a carrier frequency, a cosine signal, and an inverted sine signal; a quadrature arm coupled to receive the inverted sine signal and the output signal from the analog-to-digital converter and generate a quadrature signal; an in-phase arm coupled to receive the cosine signal and the output signal from the analog-to-digital converter and generate an in-phase signal; and an error block coupled to receive the quadrature signal and the in-phase signal and calculate the error signal. - View Dependent Claims (15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28)
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29. A method of signal processing, comprising:
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receiving a signal in a detector; digitizing the signal to form a digitized signal; determining a signal strength from an output signal of a digital phased-lock loop coupled to receive the digitized signal; and determining a modulated signal in a nested digital phased-lock loop coupled to the digital phased-lock loop, wherein the modulated signal is configured to provide data concerning a direction of a signal to distinguish a target conductor.
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30. A method of signal processing, comprising:
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receiving a signal in a detector; digitizing the signal to form a digitized signal; determining a signal strength from an output signal of a digital phased-lock loop coupled to receive the digitized signal;
wherein determining the signal strength from the output signal of the digital phase-lock loop comprises;updating an inverted sine value and a cosine value based on an error signal, mixing the inverted sine value with the signal in a quadrature arm to form a quadrature signal, mixing the cosine value with the signal in an in-phase arm to form an in-phase signal, and determining the error signal from the quadrature signal and the in-phase signal; and determining a modulated signal in a nested digital phased-lock loop coupled to the digital phased-lock loop. - View Dependent Claims (31, 32, 33, 34, 35, 36)
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37. A line locator, comprising:
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means for determining a signal strength; means for determining a signal direction in a conductor; and means for distinguishing a target conductor based on the determined signal strength and signal direction.
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38. A locator receiver, comprising:
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a first digital phase-locked loop with a first numerically controlled oscillator coupled to receive a signal and provide a first phase related to a first frequency; and a second digital phase-locked loop with a second numerically controlled oscillator coupled to receive the signal and provide a second phase related to a second frequency, wherein the signal related to the first frequency and the signal related to the second frequency determine a signal direction of a conductor. - View Dependent Claims (39, 40, 41, 42, 43)
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44. A method of determining signal direction, comprising:
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receiving a digitized signal; determining a first phase with a first digital phase-locked loop locked to a first frequency; determining a second phase with a second digital phase-locked loop locked to a second frequency; determining the signal direction in a conductor from the first frequency and the second frequency. - View Dependent Claims (45, 46)
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47. A locator receiver, comprising:
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a first digital phase-locked loop providing signals related to a first frequency of an input signal; a second digital phase-locked loop providing signals related to a second frequency of the input signal, wherein the signal related to the first frequency and the signal related to the second frequency determine a signal direction of a conductor. - View Dependent Claims (48, 49)
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Specification