Underground Line Signal Select via Phase Correlation
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Solution Overview
Problem
Conventional line location systems face challenges in accurately distinguishing between the targeted conductor and neighboring conductors due to electromagnetic field interference and bleedover currents, leading to field distortion and incorrect tracking.
Innovation Solution
A transmitter and receiver system utilizing a direct digital synthesizer to generate frequency-modulated signals, measuring phase gradients, and calculating offsets to determine signal selectivity, allowing for accurate signal strength measurement from the targeted conductor while rejecting interference from neighboring conductors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional line location systems use highly tuned filters to reject interference from outside sources, then signal-to-noise ratio is improved, but device complexity increases and response time decreases
Solution Approach 1:
The patent replaces the mechanical/electronic filter-based signal separation approach with a signal processing algorithm that uses phase information and correlation techniques. The receiver uses a correlation detector to compare the received signal with a reference signal at the active locate frequency, extracting the target conductor's signal through digital signal processing rather than analog filtering, thereby reducing hardware complexity while maintaining measurement precision.
Solution Approach 2:
The transmitter transmits the active locate frequency signal continuously or in advance, allowing the receiver to accumulate signal energy and perform correlation processing. This preliminary action of continuous transmission enables the receiver to build up sufficient signal strength before measurement, improving signal-to-noise ratio without requiring complex real-time filtering.
2Ease of operation
If conventional systems track signal strength from neighboring conductors due to bleedover, then signal strength measurement is simplified, but tracking accuracy deteriorates
Solution Approach 1:
The patent introduces phase information as an intermediary parameter to distinguish the target conductor from neighboring conductors. The receiver measures both signal strength and phase angle, using phase correlation with the transmitted active locate frequency to identify which conductor is the true target. This intermediary phase measurement allows the system to maintain simple signal strength tracking while adding discrimination capability to prevent false tracking of bleedover signals.
Solution Approach 2:
The patent exploits the asymmetric phase relationship between the transmitted active locate frequency and signals induced in neighboring conductors. The target conductor maintains a predictable phase relationship with the transmitted signal, while bleedover signals exhibit different phase characteristics. By measuring and comparing phase angles, the system can asymmetrically distinguish the true target from interfering neighboring conductors.
3Area of stationary object
If transmitters are placed at great distances from receivers to cover large areas, then coverage area is improved, but signal strength and measurement precision deteriorate
Solution Approach 1:
The transmitter continuously transmits the active locate frequency signal, allowing the receiver to accumulate signal energy over time through correlation processing. This continuous transmission maintains signal strength at the receiver despite large separation distances, enabling accurate measurement precision to be maintained across extended coverage areas without requiring high transmitter power.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system improves signal-to-noise performance and reduces the complexity of the transmitter architecture, enabling faster response times and more accurate tracking of the targeted conductor, even in complex underground environments.
Implementation Method 1
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
Implementation Method 2
The transmitter is coupled to a target conductor, either by direct electrical connection or through induction, to provide a current signal on the target conductor. The target conductor then generates an electromagnetic field at the active locate frequency in response to the current signal
Implementation Method 3
The receiver detects and processes signals resulting from the electromagnetic field generated at the target conductor as a result of the current signal
Implementation Method 4
coupling of currents from the target conductor to those neighboring conductors through various means (resistive, inductive, or capacitive), termed 'bleedover'
Data Source
AI summary
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.