Dual Oscillator Circuit for Drift-Resistant Physical Quantity Sensing
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Solution Overview
Problem
Conventional sensor circuits for sensing physical quantities, such as temperature, often require complex structures and additional circuitries to handle drifts and distortions, making them cumbersome and difficult to implement, especially in environments where a fixed reference signal is not readily available or trustworthy.
Innovation Solution
A circuit comprising two oscillator circuits with frequency dependencies on the physical quantity, where one frequency increases and the other decreases with changes in the quantity, allowing the frequency signal to convey information instead of a fixed reference signal, thereby reducing complexity and eliminating the need for a reference oscillator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional sensor circuit with a fixed reference signal is used, then the sensing function can be achieved, but the circuit complexity increases due to additional circuitries needed to handle drifts and distortions
Solution Approach 1:
The invention extracts and eliminates the reference oscillator component from the sensing circuit. By using two oscillator circuits whose frequencies both depend on the physical quantity being measured, the need for a separate fixed reference signal source is removed. This extraction of the reference oscillator reduces circuit complexity while maintaining sensing functionality through frequency comparison.
Solution Approach 2:
Instead of using one oscillator with a frequency dependent on the physical quantity and another oscillator with a fixed frequency, the invention inverts the approach by using two oscillators both with frequency-dependent operation. The reference signal is no longer fixed but varies with the physical quantity, allowing the ratio of the two frequencies to provide the measurement while eliminating the need for a stable external reference.
2Measurement precision
If a fixed reference signal source is implemented, then the sensing accuracy can be maintained, but the implementation becomes difficult in environments where a stable time basis is not available
Solution Approach 1:
The oscillator circuits serve themselves by using their own frequency variations (caused by changes in the physical quantity) as the reference for comparison. Each oscillator's frequency deviation automatically provides the reference information needed, eliminating the need for external stable time bases or environmental assumptions. The system adapts to its operating conditions through self-referencing.
Solution Approach 2:
The invention changes the parameter of the reference signal from fixed to variable, allowing it to adapt to different operating conditions. By making the reference oscillator's frequency dependent on the same physical quantity as the measurement oscillator, the system maintains measurement precision across varying environmental conditions without requiring stable external time bases.
3Device complexity
If two oscillator circuits with opposite frequency dependencies are used, then the complexity is reduced by eliminating the reference oscillator, but the circuit structure becomes more complex in terms of frequency comparison
Solution Approach 1:
The invention substitutes direct frequency comparison with a time-based measurement approach. Instead of directly comparing two frequencies (which would require complex frequency analysis circuitry), the method measures the time interval between corresponding edges of the two clock signals. This temporal measurement can be implemented with simpler digital circuitry such as counters and time-to-digital converters.
Solution Approach 2:
The invention introduces a time interval as an intermediary between the two frequency-dependent oscillators. By converting the frequency relationship into a time domain measurement (the period or phase difference between the two signals), the system simplifies the detection process. This intermediary time measurement serves as a bridge that translates complex frequency relationships into easily measurable temporal parameters.
Data Source
AI summary
A circuit for sensing a physical quantity according to an embodiment of the present invention includes a first oscillator circuit configured to provide a first clock signal including a first frequency depending on the physical quantity, and a second oscillator circuit configured to provide a second clock signal comprising a second frequency depending on the physical quantity. The circuit also includes a frequency comparator circuit configured to provide a frequency signal indicative of the physical quantity, the frequency signal being based on the first and second frequencies, wherein the first and second oscillator circuits are configured to provide the first and second clock signals such that due to a change in the physical quantity one frequency of the first and second frequencies increases, while the other frequency of the first and second frequencies decreases.