Capacitive Sensing Sinusoidal Demodulation for Odd-Harmonic Noise
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Solution Overview
Problem
Capacitive sensors are prone to external noise, particularly at odd harmonics of the operation frequency, which affects their sensitivity and accuracy in detecting touch or hover events.
Innovation Solution
The integration of a mixer and a signal generator that uses a rectified sinusoidal waveform to attenuate noise, reducing sensitivity to odd harmonics by multiplying the input signal and adjusting the attenuator gain, thereby improving the signal-to-noise ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional capacitive sensing is used, then the device can detect touch and hover events, but the sensor becomes sensitive to external noise at odd harmonics of the operation frequency
Solution Approach 1:
The patent applies sinusoidal demodulation to convert the harmful effect of odd harmonic noise into a beneficial filtering mechanism. By multiplying the sensed signal with a sinusoidal reference signal at the operation frequency and integrating the product, the system selectively passes the fundamental frequency component while rejecting odd harmonics, thus converting the noise problem into a frequency-selective measurement advantage
Solution Approach 2:
The patent changes the parameter of signal processing by introducing sinusoidal demodulation with specific frequency and phase parameters. The demodulation process uses a reference signal at the operation frequency to transform the capacitance measurement into a demodulated value that is insensitive to odd harmonic noise, effectively changing how the measurement is extracted from the raw signal
2Measurement precision
If noise attenuation is implemented using mixer and signal generator, then the signal-to-noise ratio improves, but the device complexity increases
Solution Approach 1:
The patent replaces complex physical noise filtering hardware with a computational approach using sinusoidal demodulation. Instead of using physical filters or shields to attenuate noise, the system uses mathematical operations (multiplication with reference signal and integration) to achieve noise rejection, substituting mechanical/electrical filtering with signal processing
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 solution effectively reduces noise sensitivity to odd harmonics, enhancing the accuracy and reliability of capacitive sensors by increasing the signal-to-noise ratio and minimizing the impact of external noise sources.
Implementation Method 1
systems, methods, and devices for capacitive sensing with sinusodial demodulation
Implementation Method 2
a signal generator that uses a rectified sinusoidal waveform to attenuate noise
Data Source
AI summary
Systems, methods, and devices improve the sensitivity of capacitive sensors. Devices may include an attenuator configured to receive an input from at least one sense electrode of a capacitive sensing device. The attenuator may be included in a sensing channel of a capacitive sensor. Devices may further include a signal generator coupled to an input of the attenuator. The signal generator may include one or more processors configured to generate a sinusoidal signal based, at least in part, on one or more noise characteristics of a scan sequence associated with one or more transmit electrodes of the capacitive sensing device, and provide the sinusoidal signal to the input of the attenuator.