Continuous-Time Sensor Readout Without Sample-and-Hold Noise
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Solution Overview
Problem
Traditional sensors, such as MEMS accelerometer devices, face challenges in converting electrical charges to voltage efficiently due to high power consumption and noise issues associated with the settling period and front-end amplifiers.
Innovation Solution
The approach involves continuous modulation of sensed electrical charges before transmission to an ADC, using a lower carrier frequency for modulation, eliminating the need for sample and hold, and employing a different modulation and demodulation signal to address temperature variations and improve performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional sample and hold methodology is used before ADC, then signal conversion can be performed, but power consumption increases and noise folding penalty occurs
Solution Approach 1:
The patent implements continuous-time modulation of the sensor signal without interrupting the signal flow for sampling and holding. The modulated signal is continuously processed through the ADC, eliminating the periodic settling periods required by traditional sample-and-hold circuits, thereby reducing power consumption while maintaining signal integrity.
Solution Approach 2:
The patent removes the sample and hold circuitry from the signal path entirely. By extracting this component and replacing it with continuous modulation and demodulation stages, the system eliminates the power consumption and noise folding penalties associated with traditional sampling methods while preserving the necessary signal conversion function.
2Measurement precision
If front end amplifier is used for voltage conversion, then signal can be amplified, but noise folding penalty occurs
Solution Approach 1:
The patent replaces the traditional front-end voltage amplifier with a charge-based modulation system. Instead of converting charges to voltage and amplifying the voltage signal (which introduces noise), the system modulates the charge signal directly and processes it through the ADC, eliminating the noise folding penalty while maintaining signal amplification capability through the modulation process.
3Measurement precision
If settling period is implemented for charge to voltage conversion, then signal integrity is maintained, but conversion process becomes time-intensive and power-intensive
Solution Approach 1:
The patent eliminates the settling period by implementing continuous modulation of the sensor charge signal. The modulation process occurs continuously without interruption or waiting periods, allowing the signal to be converted and processed in real-time without the time and power overhead of traditional settling periods.
4Device complexity
If single frequency is used for modulation and demodulation, then system is simple, but temperature variation affects performance
Solution Approach 1:
The patent employs asymmetric modulation and demodulation frequencies to compensate for temperature variations. By using different frequencies for modulation and demodulation, the system creates an asymmetric processing path that is less sensitive to temperature-induced frequency drift, thereby improving temperature stability without significantly increasing system complexity.
Data Source
AI summary
A system includes a sensor device, a circuit driving he sensor device at a drive frequency, a receiver, and a low pass filter. The sensor device is configured to change its electrical characteristics in response to external stimuli. The sensor device generates a modulated signal proportional to the external stimuli. The receiver is configured to receive the modulated signal and further configured to demodulate the modulated signal to generate a demodulated signal. The demodulation signal has a guard band. The receiver consumes power responsive to receiving the modulated signal. The low pass filter is configured to receive the demodulated signal and further configured to generate a sensor output.