Oscillator Sensor Interface Feedback Tuning for Drift and Mismatch
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Solution Overview
Problem
Oscillator-based sensor interfaces face accuracy limitations due to mismatches between oscillators, which result in errors such as offset, gain, and non-linearity, affecting signal conversion and requiring compensation methods like calibration and chopping techniques, but these methods do not fully address drift and other system errors.
Innovation Solution
An oscillator-based sensor interface circuit with offline or online error tuning capabilities, utilizing chopping circuitry to modulate and demodulate signals, and a tuning element to adjust oscillator frequencies and reduce detected differences, thereby compensating for oscillator mismatches and other errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional voltage conversion ADC methods are used, then high measurement precision can be achieved, but the circuit area and power consumption increase significantly
Solution Approach 1:
The patent replaces traditional voltage-based analog-to-digital conversion with a frequency-based conversion approach. Instead of using large analog building blocks and voltage comparators, the system converts the sensor signal to frequency information through oscillators, and then digitizes this frequency information using compact digital circuits. This substitution of the conversion mechanism dramatically reduces circuit area while maintaining measurement precision.
Solution Approach 2:
The patent changes the parameter domain from voltage to frequency for signal representation. By converting the sensor output voltage signal into frequency-modulated oscillator signals, the system enables the use of digital frequency counters instead of analog voltage processing circuits. This parameter transformation allows achieving the same measurement accuracy with significantly reduced hardware area.
2Area of stationary object
If frequency conversion methods are used to reduce circuit area, then measurement precision deteriorates due to oscillator mismatches and system errors
Solution Approach 1:
The patent implements feedback mechanisms where the digital frequency information is converted back to voltage signals and fed back to the sensor. This closed-loop feedback allows the system to compensate for oscillator mismatches and non-linearities by adjusting the sensor excitation signals. The feedback loop continuously corrects for systematic errors, thereby maintaining high measurement precision despite using frequency conversion methods.
Solution Approach 2:
The patent applies preliminary calibration and error compensation techniques to counteract oscillator mismatches before actual measurements are taken. By pre-characterizing the oscillator differences and applying correction factors, the system eliminates the impact of component variations on measurement accuracy. This preliminary anti-action ensures that frequency conversion does not degrade measurement precision.
3Use of energy by moving object
If oscillator-based frequency conversion is implemented, then power consumption is reduced, but accuracy is limited by oscillator mismatches and drift
Solution Approach 1:
The patent uses feedback loops to continuously monitor and correct for oscillator drift and mismatches. By comparing the frequencies of multiple oscillators and applying real-time compensation through the feedback mechanism, the system maintains accurate measurements despite power-efficient oscillator operation. The feedback ensures that power savings do not come at the cost of measurement precision.
Solution Approach 2:
The patent employs parameter modulation techniques where oscillators are modulated with chopping signals to encode measurement information. This parameter change approach allows the system to extract accurate measurements from frequency information while using low-power oscillators. The modulation scheme enables precise signal extraction even when oscillator frequencies drift, maintaining measurement accuracy with reduced power consumption.
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 proposed solution enhances the accuracy of oscillator-based sensor interfaces by detecting and reducing errors, improving matching between oscillators and compensating for system errors, leading to improved signal conversion and robustness against non-idealities.
Implementation Method 1
chopping circuitry arranged for modulating said electrical signal representative of said electrical quantity with a chopping signal
Implementation Method 2
chopping circuitry arranged for demodulating said output signals before applying said output signals to said phase detection means
Implementation Method 3
two voltage controlled oscillators (VCOs) which are matched
Implementation Method 4
phase detector (3) to compare the two oscillator outputs (41, 42) and for outputting a digital phase detection output signal
Data Source
AI summary
An oscillator-based sensor interface circuit comprises at least two oscillators, at least one of which is arranged for receiving an electrical signal representative of an electrical quantity being a converted physical quantity, phase detection means arranged to compare output signals of the at least two oscillators and for outputting a digital phase detection output signal in accordance with the outcome of the comparing, a feedback element arranged for converting a representation of the digital phase detection output signal into a feedback signal used directly or indirectly to maintain a given relation between oscillator frequencies of the at least two oscillators, detection means for detecting a difference between the at least two oscillators; and at least one tuning element arranged for receiving the detected difference and for tuning at least one characteristic of the oscillator-based sensor interface circuit.