Function generation circuit
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Solution Overview
Problem
Conventional quartz oscillation apparatuses with temperature compensation functions face challenges such as frequency skipping, clock noise, and adjustment errors due to quantized noise and the need for increased memory volume to achieve accurate temperature compensation, leading to basic frequency fluctuation errors of ±1.0 ppm, which is not sufficient for modern electronic devices requiring ±0.5 ppm accuracy.
Innovation Solution
A function generation circuit that includes multiple analog signal generation circuits, approximation function generation circuits, and peak change point adjustment circuits to generate control signals approximating third, fourth, fifth, and higher-order temperature functions, allowing for precise temperature compensation across a broad temperature range without increasing circuit size or introducing noise, thereby stabilizing the oscillation frequency within ±0.5 ppm.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If A/D conversion is used to obtain crossover approximation for control voltage generation, then temperature compensation can be implemented, but quantized noise occurs and frequency skipping cannot be avoided
Solution Approach 1:
The patent replaces the A/D conversion-based digital control system with an analog signal processing system. Temperature detection, control voltage generation, and compensation control are all performed using analog circuits, eliminating the quantized noise inherent in digital conversion processes while maintaining temperature compensation functionality.
2Measurement precision
If the number of temperature domains is increased to reduce adjustment error, then measurement precision improves, but memory volume increases
Solution Approach 1:
The patent replaces the memory-based digital storage approach with analog circuit implementation. Temperature domain characteristics are implemented through analog circuit parameters rather than stored in memory, eliminating the need for increased memory volume while maintaining high adjustment precision across multiple temperature domains.
3Stability of the object's composition
If a clock signal generation circuit is added for temperature compensation, then frequency stabilization is achieved, but clock noise mixing occurs
Solution Approach 1:
The patent replaces the clock signal generation circuit with an analog control system that directly adjusts the oscillator frequency based on temperature. This eliminates the need for separate clock generation and avoids the introduction of clock noise into the frequency stabilization process.
4Stability of the object's composition
If sample holding circuit time constant is increased for frequency stabilization, then frequency stability improves, but power-on stabilization time increases
Solution Approach 1:
The patent replaces the sample holding circuit with an analog control system that provides immediate frequency adjustment response. The analog circuitry naturally responds to temperature changes without requiring long time constants for stabilization, reducing power-on time while maintaining frequency stability.
Data Source
AI summary
A first order function generation circuit receives a signal from a temperature sensor circuit, and generates a first order function control signal V1 that is affected by the ambient temperature. A fourth order and fifth order approximation function generation circuit receives signals from the temperature sensor circuit and from the third order approximation function generation circuit, and generates a fourth and fifth order approximation function control signal V45 that is affected by the ambient temperature. A peak change point adjustment circuit outputs a signal to adjust the value of a peak change point temperature Ti for the third order approximation function generation circuit, the first order generation function circuit and the fourth order and fifth order approximation function generation circuit. A temperature compensation circuit adds together control signals V0, V1, V3 and V5, and outputs the resultant signal Vc.