Resonant Inductive Pulse Shaping for Reduced Noise Folding
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Solution Overview
Problem
Resonant inductive sensors face noise interference at harmonics of the resonant frequency, which affects the accuracy of position, proximity, and physical state sensing due to uncertainties in signal energy and modulation period duration.
Innovation Solution
The implementation of drive current pulse shaping, synchronized with the resonator oscillation frequency, ensures that each pair of drive current pulses within a modulation period is substantially identical, thereby reducing noise folding by down modulating signal energy around harmonics and attenuating noise caused by uncertainty in the modulation period duration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resonant inductive sensing is used to detect changes in resonator impedance, then sensing capability for position, proximity, or physical state is achieved, but noise interference appears at harmonics of the resonant frequency
Solution Approach 1:
The patent applies periodic drive current pulses synchronized with the resonator oscillation frequency. By using periodic excitation at the fundamental frequency rather than continuous or broadband excitation, the system selectively stimulates the resonator at its fundamental mode while minimizing excitation of harmonic frequencies, thereby reducing noise folding at harmonics and improving signal-to-noise ratio for impedance detection.
Solution Approach 2:
The patent changes the temporal parameters of the drive current (using pulsed excitation with specific duty cycle and timing synchronized to the oscillation period) to selectively excite only the fundamental resonant frequency. This parameter optimization ensures that energy is concentrated at the fundamental frequency while harmonic content is minimized, reducing noise interference during sensing.
2Reliability
If drive current is used to maintain resonator oscillation, then resonance state is sustained, but noise folding occurs due to down modulation of signal energy around harmonics
Solution Approach 1:
The system uses periodic drive current pulses that are synchronized with the resonator oscillation period. This periodic excitation maintains the resonance state by replenishing energy at the fundamental frequency while avoiding excitation of harmonic frequencies. The periodic timing ensures that each pulse occurs at the optimal phase to sustain oscillation without introducing harmonic distortion that would cause noise folding.
3Adaptability or versatility
If modulation period duration varies, then adaptation to different resonator frequencies is possible, but uncertainty in modulation period duration causes noise
Solution Approach 1:
The system employs feedback mechanisms to detect the actual resonator oscillation frequency and adjust the modulation period accordingly. By continuously monitoring the resonator response and synchronizing the drive current pulses to the detected oscillation period, the system maintains accurate timing even when resonator frequency varies, thereby eliminating noise caused by timing uncertainty while preserving adaptability to different resonator conditions.
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
This approach effectively reduces noise interference, enhancing the accuracy of resonant inductive sensing by maintaining a constant resonator oscillation amplitude and improving the precision of sensor response data, particularly in detecting changes in resonator impedance caused by conductive targets.
Implementation Method 1
a resonator configured for operation in a resonance state (resonant frequency and amplitude)
Implementation Method 2
in case of inductive sensing, the resonator includes an inductive sensing coil that, operated at resonance, projects a magnetic sensing field
Implementation Method 3
resonance is affected by a storage or loss in projected magnetic flux energy output from the inductive sensing coil, such as caused by the eddy current effect associated with a conductive target
Data Source
AI summary
A resonant inductive sensing system includes in the drive current signal path of the resonator a pulse shaper for noise reduction, including reducing noise resulting from down modulation of signal energy around harmonics of the oscillator (multiples of the resonance frequency), and from uncertainty in the duration of the oscillation period. The pulse shaper is configured so that, for each modulation period of the drive current, consecutive drive current pulses are substantially identical. In example embodiments, an inductance-to-digital conversion (IDC) unit includes drive circuitry configured to drive excitation current pulses to the resonator with a modulation period synchronized with a resonator oscillation frequency, and pulse shaping circuitry configured to pulse shape the drive current pulses so that each pair of drive current pulses within a modulation period are substantially identical.