Variable Capacitor Sensor Signal Compensation for Nonlinear Distortion
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Solution Overview
Problem
Variable capacitors in applications like microphones face challenges in accurately detecting capacitance variations due to nonlinear signal effects, especially at high sound levels, leading to reduced accuracy in determining capacitance changes.
Innovation Solution
An apparatus comprising a sensor unit and a compensation unit is used to generate a sensor signal indicating capacitance variations in a variable capacitor, where the compensation unit reduces nonlinear signal portions by influencing the sensor signal with a compensation signal, thereby improving accuracy. This apparatus includes a bias voltage unit, an inverting amplifier with capacitive feedback, and an analog-to-digital converter, and can utilize a double backplate configuration to minimize nonlinear effects.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a variable capacitor is used to detect capacitance variations in applications like microphones, then the sensor can operate across a wide range of applications, but nonlinear signal effects occur especially at high sound levels, leading to reduced accuracy in determining capacitance changes
Solution Approach 1:
The variable capacitor is divided into two separate capacitors (first variable capacitor and second variable capacitor) with identical membrane structures. Each capacitor handles a portion of the measurement, and their signals are combined to cancel nonlinear effects. This segmentation allows the system to maintain versatility across applications while improving measurement precision by eliminating nonlinear distortions at high sound levels.
2Device complexity
If a single variable capacitor with a membrane and backplate is used, then the device structure is simple, but nonlinear signal portions reduce the accuracy of capacitance determination
Solution Approach 1:
Instead of using a single variable capacitor, the invention segments the measurement function into two identical variable capacitors. Each capacitor has its own membrane and backplate structure. By measuring both capacitors simultaneously and combining their signals, the nonlinear portions cancel out, significantly improving capacitance determination accuracy while maintaining relatively simple individual capacitor structures.
Solution Approach 2:
The invention uses feedback by measuring the output signals from both variable capacitors and combining them in a specific manner. The output signal is derived from the difference between the two capacitor measurements, which inherently cancels nonlinear distortions. This feedback mechanism ensures accurate capacitance determination even when individual capacitors exhibit nonlinear behavior at high sound levels.
3Productivity
If the variable capacitor operates at high sound pressure levels, then the dynamic range of the sensor is extended, but nonlinear signal effects increase, reducing measurement accuracy
Solution Approach 1:
The invention segments the measurement into two parallel capacitor paths that operate simultaneously at high sound pressure levels. By using two identical variable capacitors with membranes and backplates, the system can handle extended dynamic ranges while the differential measurement approach cancels nonlinear signal effects, maintaining measurement accuracy even at high sound levels.
Solution Approach 2:
The invention converts the harmful nonlinear signal effects into a beneficial cancellation mechanism. By using two identical variable capacitors subjected to the same nonlinear distortions at high sound pressure levels, the nonlinear portions appear identically in both measurements and cancel out when the signals are combined. This transforms the harmful nonlinear effects into a benefit, allowing accurate measurements across an extended dynamic range including high sound pressure levels.
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 solution significantly reduces nonlinear signal portions, enhancing the accuracy of capacitance determination and extending the dynamic range of the sensor, allowing for better performance at higher sound pressure levels.
Implementation Method 1
Pressure changes lead to changes in the distance between the plates of the capacitor causing a variation of the capacitance
Implementation Method 2
the sensor unit comprises an inverting amplifier with a capacitive feedback connection to an inverting input of the amplifier
Data Source
AI summary
An apparatus for generating a sensor signal indicating information on a capacitance of a variable capacitor including a variable capacitance includes a sensor unit and a compensation unit. The sensor unit is configured to generate a sensor signal indicating information on a varying current flowing through a connection between the sensor unit and the variable capacitor caused by a variation of the capacitance of the variable capacitor while the variable capacitor is biased by a predefined bias voltage. Further, the compensation unit is configured to influence the sensor signal or to provide a compensation signal capable of influencing the sensor signal so that the sensor signal includes less nonlinear signal portions than a sensor signal without the influence of the compensation unit or the compensation signal.