MEMS C2V Offset Cancellation Using Variable Capacitor Feedback
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Solution Overview
Problem
MEMS sensors, particularly gyroscopes, face challenges with offset signal portions that occupy a significant portion of the dynamic range, leading to reduced C2V amplifier gain and increased ADC noise, which affects noise performance.
Innovation Solution
Implementing a feedback loop with a capacitive DAC modulated by a sigma-delta modulator to dynamically cancel offset signals, using variable capacitors to adjust capacitance and maintain the offset at zero, allowing for increased C2V amplifier gain and reduced ADC noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If offset signal portion is present in the C2V converter output, then the dynamic range is occupied by offset, but the C2V amplifier gain is reduced and ADC noise increases
Solution Approach 1:
The patent implements a feedback loop where the C2V converter output is fed back to a control system that dynamically adjusts variable capacitors to cancel offset signals. The control system monitors the output signal, identifies offset components, and generates control signals to modify the variable capacitors in real-time, creating a closed-loop system that continuously suppresses offset while maintaining measurement precision.
Solution Approach 2:
The patent introduces variable capacitors as intermediary elements between the C2V converter and the output stage. These variable capacitors act as mediators that can be dynamically adjusted to cancel offset signals. The capacitors are controlled by control circuitry that modulates their capacitance values to counteract offset components, effectively using them as adjustable intermediaries to improve noise performance.
2Measurement precision
If variable capacitors are used for offset cancellation, then offset signal portion is removed, but the device complexity increases
Solution Approach 1:
The patent merges the offset cancellation function with the existing C2V converter architecture by integrating variable capacitors into the sense path. The control circuitry for the variable capacitors is combined with the C2V converter control system, allowing offset cancellation to be achieved without adding completely separate control hardware. This merging approach reduces overall system complexity while maintaining effective offset suppression.
Solution Approach 2:
The system employs self-service mechanisms where the control circuitry automatically monitors the C2V converter output and autonomously adjusts the variable capacitors to cancel offset signals without external intervention. The feedback loop enables the system to self-regulate and maintain optimal operating conditions, reducing the need for complex external control systems and manual calibration.
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 enhances the C2V amplifier gain for the signal of interest, suppressing ADC noise and improving overall gyroscope system noise performance by effectively eliminating the offset signal portion.
Implementation Method 1
one or more variable capacitors coupled to the sense path and processing circuitry... generate a variable capacitor control signal to modify a capacitance of the one or more variable capacitors
Data Source
AI summary
In a microelectromechanical system (MEMS) sensor, movement of a component such as a proof mass due to a force of interest is sensed capacitively. A capacitance-to-voltage (C2V) converter receives a capacitance signal from the sensor and outputs a signal that includes an offset in addition to a signal of interest. The output signal is analyzed to identify the offset portion of the output signal and to modify values one or more variable capacitors coupled to the C2V input reduce the offset portion of the output signal.