Reference Coil Noise Cancellation for Transient EM Detection
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Solution Overview
Problem
Existing transient electromagnetic methods face challenges in achieving optimal denoising due to low signal-to-noise ratios and interference from electromagnetic noise, especially in urban environments, leading to inaccurate underground electrical structure analysis.
Innovation Solution
A reference noise cancellation device and method utilizing a signal coil and a reference coil, synchronized by a timing sequence generator, to separately record induced magnetic fields and electromagnetic noise, applying a reference noise cancellation algorithm to subtract estimated noise from the signal coil data, enhancing data quality and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If transient electromagnetic field method is used to observe induced magnetic field, then underground electrical structure information can be obtained, but the signal-to-noise ratio is low making accurate reflection difficult
Solution Approach 1:
The patent segments the measurement process into two separate channels: a signal acquisition channel that captures both the induced magnetic field and electromagnetic noise, and a reference acquisition channel that captures only the electromagnetic noise. This segmentation allows for separate processing and subsequent subtraction of noise from the signal channel, thereby improving measurement precision by isolating and removing the harmful noise component.
Solution Approach 2:
The patent introduces a reference coil as an intermediary element that does not participate in the main signal detection but specifically captures the electromagnetic noise environment. This reference channel acts as a mediator that provides noise information which is then used to cancel noise from the primary signal channel, effectively separating the harmful noise from the useful signal.
2Reliability
If direct noise separation from field observation data is attempted, then noise removal is pursued, but optimal denoising performance cannot be achieved due to data uncertainty and non-steady state characteristics
Solution Approach 1:
The patent performs preliminary noise characterization by continuously monitoring the electromagnetic noise environment through the reference coil before and during signal acquisition. This preliminary action of capturing noise data in advance allows the system to adapt to changing noise conditions and apply appropriate denoising processing, improving reliability without requiring complex real-time analysis of uncertain field data.
Solution Approach 2:
The patent implements a feedback mechanism where the noise data from the reference channel is continuously fed back to the signal processing system. This feedback loop enables dynamic noise cancellation by constantly updating the noise estimate and subtracting it from the signal channel, achieving optimal denoising performance while maintaining manageable processing complexity through a closed-loop control approach.
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 method effectively reduces both steady-state and unsteady-state noise, improving data quality and detection accuracy, enabling applications in noisy environments such as urban underground spaces and mine water inrush detection.
Implementation Method 1
Based on Faraday's law of electromagnetic induction, the transient electromagnetic field is performed by injecting current into the loop laid on the ground. After the current is stabilized, the current will be turned off suddenly. The fast changes in current will generate pulsed magnetic fields in the subsurface.
Implementation Method 2
When the geological bodies in the subsurface are stimulated by the pulsed magnetic field, they will generate induced currents, which in turn will generate induced magnetic fields.
Implementation Method 3
The signal coil is configured to receive the induced magnetic field of underground conductors and the surrounding magnetic field noise.
Data Source
AI summary
A reference noise cancellation device for a transient electromagnetic field is provided. The device includes a transmitter, a transmitting loop, a reference coil, a signal coil and a receiver. The transmitter generates a measurement timing sequence to trigger the receiver to synchronously record the induction signal in the signal coil and the electromagnetic noise in the reference coil. A bipolar current waveform is generated and is injected into the transmitting loop through the first connecting line. The signal coil receives an induced magnetic field of an underground conductor and surrounding magnetic field noise. The reference coil receives surrounding electromagnetic noise. The receiver receives and records the induced magnetic field and surrounding electromagnetic noise of the underground conductor in the signal coil and the surrounding electromagnetic noise in the reference coil.