Digital Frequency Compensation Circuit for Crystal Oscillator Drift
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Solution Overview
Problem
Electronic systems face performance degradation due to frequency instability in frequency sources, such as crystal oscillators, which result in frequency deviations of tens or hundreds of ppm, affecting applications like cellular networks and time protocols, requiring effective frequency compensation without modifying the source structure.
Innovation Solution
A frequency compensator comprising a control circuit and a frequency compensation circuit that generates a frequency control word based on an initial and target frequency, using a Time-Average-Frequency Direct Period synthesizer to adjust the frequency, allowing for precise compensation and stability enhancement without altering the physical structure of the frequency source.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a crystal oscillator is used as a frequency source, then the electronic system can operate with a basic frequency source, but the frequency deviation of tens or hundreds of ppm causes performance degradation
Solution Approach 1:
The patent introduces a frequency compensator as an intermediary device between the crystal oscillator and the electronic system. This compensator includes a phase-locked loop (PLL) that generates a compensated clock signal by comparing the actual frequency with the target frequency and adjusting accordingly. The compensator acts as a mediator that corrects the frequency deviation without requiring modification of the original crystal oscillator, thus resolving the contradiction between maintaining basic frequency source operation and achieving high frequency precision.
Solution Approach 2:
The patent changes the frequency parameter through digital control mechanisms. The frequency compensator uses a frequency control word (FCW) to adjust the output frequency of the PLL, enabling dynamic frequency compensation. By changing the control parameters of the frequency synthesizer, the system can correct frequency deviations of tens or hundreds of ppm and achieve much higher frequency precision, thereby resolving the contradiction between simple operation and high precision requirements.
2Measurement precision
If the frequency source structure is modified to improve frequency stability, then frequency precision can be enhanced, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent segments the frequency compensation function into a separate, modular frequency compensator unit that can be independently designed and implemented. This compensator is further divided into functional blocks including a frequency detector, phase-locked loop, and frequency synthesizer. By segmenting the system, the complexity is managed locally in the compensator module while the main frequency source remains simple, thus resolving the contradiction between enhanced precision and reduced overall structure complexity.
Solution Approach 2:
The patent replaces potential mechanical or hardware modifications to the crystal oscillator with an electronic/digital frequency compensation system. Instead of physically altering the frequency source to improve stability, the solution uses electronic signal processing through the PLL and digital frequency control. This substitution achieves high frequency precision without modifying the physical structure of the original frequency source, thereby reducing device complexity and manufacturing costs.
3Reliability
If high-precision frequency compensation is implemented, then frequency stability is improved, but the device complexity and implementation cost increase
Solution Approach 1:
The patent uses a frequency synthesizer that generates a compensated clock signal by copying and adjusting the reference frequency from the crystal oscillator. The phase-locked loop creates a copy of the frequency signal and modifies it digitally through the frequency control word to achieve the target frequency. This copying approach allows high-precision frequency compensation to be implemented through software or programmable logic device configurations rather than expensive custom hardware, thereby improving frequency stability while reducing implementation costs.
Data Source
AI summary
A frequency compensator, an electronic device, and a frequency compensation method are disclosed. The frequency compensator includes a control circuit and a frequency compensation circuit. The control circuit is configured to generate a frequency control word according to an initial frequency and an target frequency. The frequency compensation circuit is configured to receive an input signal of an initial frequency, and to generate and output an output signal of a compensated frequency according to the frequency control word and the input signal of the initial frequency.