Capacitive Sensor Phase Correction for Clock Jitter
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Solution Overview
Problem
Capacitive sensors face challenges in distinguishing between external noise and signal components when they share the same frequency as the driving voltage, and existing solutions fail to suppress variations in detection values caused by phase changes in digital circuit clock signals.
Innovation Solution
A sensor device with a sensor unit, reference signal generator, analog-digital converters, demodulating units, and a correcting unit that adjusts the relative phases of sinusoidal signals to remove harmonic components and correct demodulated signals for phase variations, ensuring stable detection values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Extent of automation
If demodulation processing is performed using a digital circuit synchronized with a clock signal, then the detection process can be automated and standardized, but variations in the clock signal phase cause variations in the detection value
Solution Approach 1:
The patent implements feedback by detecting the phase of the clock signal and using this information to adjust the phase of the sinusoidal wave generated by the digital circuit. The phase detection unit monitors clock phase variations, and the phase adjustment unit compensates for these variations by modifying the sinusoidal wave phase, thereby maintaining stable detection values despite clock signal fluctuations.
Solution Approach 2:
The patent changes the phase parameter of the sinusoidal wave dynamically based on clock signal conditions. By adjusting the phase of the sinusoidal wave in response to detected clock phase variations, the system maintains optimal demodulation conditions and eliminates detection value variations caused by clock instability.
2Measurement precision
If the relative phases of driving and demodulation sinusoidal components are adjusted to maximize detection sensitivity, then detection sensitivity is improved, but phase variations over time cause detection value variations
Solution Approach 1:
The system continuously monitors the phase relationship between the clock signal and the sinusoidal wave, and dynamically adjusts the sinusoidal wave phase to maintain optimal alignment. This feedback mechanism ensures that detection sensitivity remains maximized while compensating for phase drift over time.
Solution Approach 2:
The patent transitions from a static phase adjustment approach to a dynamic one, where the phase of the sinusoidal wave is continuously adapted based on real-time clock phase detection. This dynamic adjustment maintains optimal detection sensitivity despite temporal phase variations.
3Measurement precision
If a sinusoidal alternating voltage is applied to detect capacitance changes, then capacitance detection can be performed, but external noise with the same frequency cannot be distinguished from the signal
Solution Approach 1:
The patent introduces phase information as an intermediary parameter to distinguish signal from noise. By analyzing the phase relationship between the applied sinusoidal voltage and the resulting current, the system can identify the capacitive component of the current, which has a specific phase relationship with the driving voltage, while rejecting noise components with different phase characteristics.
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 sensor device effectively suppresses variations in detection values due to phase changes in digital circuit clock signals, enhancing detection sensitivity and accuracy by correcting relative phases and removing harmonic components.
Implementation Method 1
A capacitive sensor that detects a change in capacitance is widely used... A general capacitive sensor has: electrodes (conductors) used to form a capacitor that causes a change in capacitance
Implementation Method 2
a detection value for capacitance is obtained by performing demodulation in which an output signal from the capacitance detection circuit is multiplied by a sinusoidal wave having substantially the same phase (frequency) as a sinusoidal wave used for driving
Implementation Method 3
When a low-pass filer is applied to the multiplication result to remove the harmonic component, the direct-current component is extracted
Data Source
AI summary
A sensor device includes a sensor unit that generates a detection signal having the same detection frequency as an entered sinusoidal analog signal and matching a physical quantity to be detected; a reference signal generating unit that generates a reference signal having the detection frequency, according to the entered analog signal; converting units that convert the detection signal and reference signal to digital signals in synchronization with a clock signal; a demodulating unit that multiplies the digital detection signal by each of two sinusoidal synchronization signals having the detection frequency, the phases of the two synchronization signals being shifted from each other by one-fourth of a cycle, and generates two demodulated signals free from a harmonic component; and a correcting unit that corrects the demodulated signals according to the digital reference signal so as to suppress variations, in the demodulated signals, caused by variations in the clock signal phase.