Expanded Pull Range Voltage Controlled Clock Synthesizer
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Traditional clock sources, such as crystal oscillators, have limited frequency pull ranges due to manufacturing constraints, making it difficult to generate a wide range of frequencies required by modern network equipment, which leads to complexity and reliability issues in timing subsystems.
Innovation Solution
A controllable oscillator circuit that dynamically adjusts its frequency using a digital control signal based on a reference control value and voltage control input, allowing for a continuous frequency range of operation and expanded pull range, enabling the generation of low-jitter, high-frequency clock signals across a broad frequency spectrum.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a traditional crystal oscillator is used with a fixed resonator frequency, then manufacturing precision and initial frequency accuracy are improved, but the frequency pull range is limited and device complexity increases when multiple frequencies are needed
Solution Approach 1:
The patent applies dynamics by making the resonator frequency可调 (adjustable) through a voltage-controlled oscillator (VCO) that can dynamically tune the output frequency across a wide range (e.g., 100 MHz to 1 GHz). The VCO uses a varactor diode whose capacitance changes with applied voltage, enabling continuous frequency adjustment without requiring multiple fixed-frequency resonators. This resolves the contradiction by providing both frequency accuracy (through controlled tuning) and adaptability (through wide frequency range).
Solution Approach 2:
The patent changes the electrical parameter (capacitance) of the resonator circuit by introducing a varactor diode whose capacitance varies with reverse bias voltage. By changing this electrical parameter dynamically, the resonator's oscillation frequency can be tuned across a wide range while maintaining stability. This allows a single resonator to replace multiple fixed-frequency resonators, reducing device complexity while expanding frequency versatility.
2Adaptability or versatility
If a voltage controlled oscillator (VCO) is used to achieve wide frequency range, then adaptability is improved, but phase noise performance deteriorates due to higher losses in variable elements
Solution Approach 1:
The patent uses partial action by combining a fixed-frequency resonator (providing stable baseline performance) with a VCO tuning mechanism (providing frequency flexibility). The resonator operates at its optimal fixed frequency point, while the VCO makes controlled adjustments within a moderate pull range (e.g., ±50 ppm). This hybrid approach captures most of the phase noise benefits of fixed resonators while achieving sufficient frequency adaptability for many applications.
3Adaptability or versatility
If multiple discrete oscillators are used to support various reference clock frequencies, then frequency versatility is improved, but device complexity and system reliability worsen
Solution Approach 1:
The patent applies universality by designing a single VCXO device that can generate multiple reference clock frequencies (e.g., 622.08 MHz, 644.53 MHz, 657.42 MHz, 690.57 MHz) required for different protocols (SONET/SDH, Ethernet, Fibre Channel). The voltage-controlled resonator serves multiple frequency requirements that would traditionally need separate oscillators, thereby reducing device complexity while maintaining frequency versatility.
4Adaptability or versatility
If the pull range of a resonator is expanded to cover wider frequency ranges, then frequency adaptability is improved, but manufacturing precision and frequency stability deteriorate
Solution Approach 1:
The patent employs feedback through a phase-locked loop (PLL) that monitors the output frequency of the VCXO and adjusts the control voltage to maintain the desired frequency. The PLL compares the VCXO output with a stable reference frequency and generates an error signal that corrects frequency deviations. This feedback mechanism allows the resonator to operate over an expanded pull range while maintaining frequency stability and precision through continuous correction.
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
This solution provides a cost-effective clock source with improved phase noise performance, reduced jitter, and enhanced reliability by allowing a single resonator to generate a wide range of frequencies, simplifying timing subsystems and reducing the need for multiple oscillators.
Implementation Method 1
the variable elements (e.g., the varactor) associated with the VCO used to vary the frequency typically have higher losses than fixed elements such as the capacitors in a fixed source
Data Source
AI summary
A technique provides a clock source that meets accuracy requirements, allows the use of a low cost resonator, provides a wide range of output frequencies, and provides suitable phase noise performance. The technique generates a clock signal having a target output frequency using a controllable oscillator having at least one continuous frequency range of operation. The technique dynamically adjusts a reference control value based on a voltage for adjusting a frequency of the clock signal around a frequency determined by the reference control value. The reference control value is adjusted to be approximately within the center of an actual pull range corresponding to the controllable oscillator and a voltage control input of the controllable oscillator. The effective pull range of the controllable oscillator is continuous across the at least one continuous frequency range of operation.