Magnetic Detection With Spread-Spectrum Signals to Reduce Beat Noise
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Solution Overview
Problem
Conventional fluxgate sensors suffer from reduced detection accuracy due to beat signals when the frequency of the magnetic field to be detected is close to the excitation frequency or its multiples, leading to noise interference.
Innovation Solution
A magnetic detection apparatus with a signal converter that generates excitation and detection signals with spread spectra, where the detection frequency is twice the excitation frequency, and a low-pass filter to attenuate frequencies above a cutoff frequency, reducing beat signal interference.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional fluxgate sensors use a fixed excitation frequency, then the device structure is simple and easy to operate, but detection accuracy deteriorates when the magnetic field frequency is close to the excitation frequency or its multiples due to beat signal interference
Solution Approach 1:
The patent applies parameter changes by using a spread spectrum excitation signal that varies the excitation frequency over time across a range of frequencies rather than using a fixed frequency. This allows the sensor to avoid beat signal interference by distributing the excitation energy across multiple frequencies, thereby maintaining high detection accuracy even when the magnetic field frequency is close to any single excitation frequency. The signal converter processes the detected signal by correlating it with the known spread spectrum sequence to recover the magnetic field information.
2Measurement precision
If the excitation frequency is kept constant, then the device is easy to operate and maintain, but noise interference increases when detecting magnetic fields with frequencies close to the excitation frequency or its multiples
Solution Approach 1:
The patent applies dynamics by making the excitation frequency dynamic rather than static. The spread spectrum technique continuously varies the excitation frequency according to a predetermined code sequence, transforming the system from a static single-frequency operation to a dynamic multi-frequency operation. This dynamic approach allows the system to adapt to different detection conditions and avoid fixed frequency interference, significantly improving the signal-to-noise ratio while the automated processing maintains operational simplicity.
3Measurement precision
If spread spectrum signals are used to reduce beat signal interference, then detection accuracy is improved, but the device complexity increases due to additional signal conversion and processing components
Solution Approach 1:
The patent introduces a signal converter as an intermediary component that bridges the detector output and the final measurement output. This signal converter performs correlation processing with the known spread spectrum code to decode the modulated signal and extract the magnetic field information. By using this intermediary processing stage, the system achieves high detection accuracy through spread spectrum techniques while keeping the overall architecture modular and manageable, rather than requiring complete redesign of the entire sensing system.
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
Enhances detection accuracy by minimizing beat signal noise, allowing precise measurement of magnetic fields even when their frequencies are close to the excitation frequency or its multiples.
Implementation Method 1
an exciter configured to excite the core with an excitation signal, a detector configured to detect induced voltage according to a time change of magnetic flux generated by the core
Implementation Method 2
a core to which magnetism to be detected is applied, an exciter configured to excite the core with an excitation signal
Data Source
AI summary
A magnetic detection apparatus includes a core to which magnetism to be detected is applied, an exciter configured to excite the core with an excitation signal, a detector configured to detect induced voltage according to a time change of magnetic flux generated by the core, a wave detector configured to detect a wave from a signal corresponding to the induced voltage by using a detection signal corresponding to the excitation signal and to generate a signal according to the magnetism to be detected, and a signal converter configured to generate and output to the exciter an excitation signal that has a spread spectrum of a signal having an excitation frequency and to generate and output to the wave detector a detection signal that has a spread spectrum of a signal having a detection frequency of twice the excitation frequency.