DCXO Startup Using Injection-Locked Ring Oscillator Support
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Solution Overview
Problem
Digitally controlled crystal oscillators (DCXO) require significant time to reach a desired frequency at startup and during frequency changes, leading to initial signal mismatch and potential interference in communication systems that demand high precision.
Innovation Solution
The implementation of an Injection-Locked Ring Oscillator (ILRO) system, which uses the ILRO output as a clock source during startup and frequency adjustments to accelerate DCXO initialization and compensate for phase noise, allowing the DCXO to lock onto the desired frequency more quickly and maintain low phase noise levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a DCXO system is used to control crystal oscillator frequency precisely, then frequency precision is improved, but startup time and frequency change time are significantly increased
Solution Approach 1:
The patent applies preliminary action by pre-loading the DCXO with initial frequency values stored in a lookup table based on temperature compensation data. This preliminary preparation allows the oscillator to start closer to the target frequency, significantly reducing the time required to reach the desired frequency while maintaining precision requirements.
Solution Approach 2:
The patent introduces an intermediary frequency synthesis stage between the crystal oscillator and the final output. This intermediary uses a phase-locked loop (PLL) or direct digital synthesis (DDS) mechanism to rapidly generate the desired frequency during startup, while the DCXO provides precise frequency control once stabilized, thus resolving the time-precision tradeoff.
2Measurement precision
If a DCXO system is used to adjust resonant frequency, then frequency control precision is improved, but phase noise increases during frequency changes
Solution Approach 1:
The patent employs periodic action by using a reference oscillator that continuously provides a stable frequency reference. During frequency changes, the system periodically samples and locks to this reference, maintaining low phase noise while achieving precise frequency control through the DCXO's digital adjustment capability.
Solution Approach 2:
The patent implements feedback mechanisms where the output frequency is continuously monitored and compared against the desired frequency. This feedback loop allows the DCXO to make precise adjustments while maintaining stable phase characteristics, reducing phase noise during frequency transitions by continuously correcting deviations.
3Adaptability or versatility
If DCXO codes are changed to modify operating frequency, then frequency adaptability is improved, but signal mismatch occurs during transition
Solution Approach 1:
The patent applies dynamics by implementing a dynamic frequency switching strategy that adjusts the switching speed and method based on the current operating state. During frequency changes, the system dynamically transitions between different frequency sources or uses frequency sweeping techniques to maintain continuous, mismatch-free signal output while achieving wide frequency adaptability.
Solution Approach 2:
The patent uses beforehand cushioning by preparing frequency transition paths in advance and using buffer stages or filtering mechanisms that smooth out transitions. This prevents signal mismatch during frequency changes by anticipating and compensating for potential discontinuities before they occur, maintaining signal reliability while enabling frequency adaptability.
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 approach significantly reduces the time required for DCXO to reach a stable frequency, ensuring rapid synchronization and minimizing interference in communication systems by using the ILRO to support the DCXO during initial startup and frequency adjustments.
Implementation Method 1
An oscillator system includes a digitally controlled crystal oscillator (DCXO) circuit, an injection-locked ring oscillator (ILRO) circuit, and a control state machine. The ILRO circuit is utilized to generate an oscillating signal at a desired frequency.
Implementation Method 2
The DCXO circuit is configured to lock onto a desired frequency in response to the oscillating signal. The control state machine causes the DCXO circuit to lock onto the desired frequency in response to the oscillating signal from the ILRO circuit.
Data Source
AI summary
Methods and systems to provide digitally controlled crystal oscillators are disclosed. One example method includes determining a state of an oscillator system and selecting a first output of a digitally controlled crystal oscillator or a second output of a second oscillator based on the determination. In an example implementation, the second oscillator is a ring oscillator.