Injection-Locked PLL Ring Oscillator for Low-Jitter Phase Control
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Solution Overview
Problem
Conventional injection-locked PLL circuits face difficulties in achieving frequency convergence and phase control due to the need for initialization processing, which complicates phase control and increases phase jitter.
Innovation Solution
The proposed injection-locked PLL circuit employs a phase frequency detector, charge pump, loop filter, and a voltage-controlled oscillator with a ring oscillator structure, where the active number of delay elements is controlled based on detection signals to synchronize the output signal with a reference signal, eliminating the need for initialization processing and reducing phase jitter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If initialization processing is performed to determine frequency convergence before phase control, then frequency stability is improved, but device complexity and processing time increase
Solution Approach 1:
The patent applies preliminary action by performing frequency convergence determination before phase control initialization. The control unit determines whether the frequency of the voltage-controlled oscillator has converged to the reference frequency before enabling phase control, ensuring frequency stability is established first. This preliminary frequency check prevents phase control from operating on an unstable frequency basis, thereby improving reliability while managing complexity through a structured sequential approach.
2Reliability
If initialization processing is performed to determine frequency convergence, then frequency stability is improved, but phase control difficulty increases
Solution Approach 1:
The patent applies preliminary action by performing frequency convergence determination before phase control initialization. The control unit determines whether the frequency of the voltage-controlled oscillator has converged to the reference frequency before enabling phase control, ensuring frequency stability is established first. This preliminary frequency check prevents phase control from operating on an unstable frequency basis, thereby improving reliability while managing complexity through a structured sequential approach.
3Ease of operation
If delay circuit is used to generate pulse signal based on reference signal, then phase control is enabled, but pulse width becomes sensitive to power supply voltage and process fluctuations
Solution Approach 1:
The patent applies parameter changes by using a different signal generation approach that is less sensitive to voltage and process variations. Instead of relying on a delay circuit whose pulse width varies with power supply voltage and process fluctuations, the invention uses an alternative mechanism (such as a differentiator circuit or edge-triggered mechanism) to generate the injection signal from the reference signal. This changes the operating parameters of the signal generation process to achieve more stable pulse width while maintaining phase control capability.
4Loss of time
If injection signal is supplied before frequency convergence, then phase control can start earlier, but frequency convergence becomes difficult
Solution Approach 1:
The patent applies preliminary action by performing frequency convergence determination before enabling phase control. The control unit monitors whether the frequency of the voltage-controlled oscillator has converged to the reference frequency and only then activates phase control functionality. This ensures that phase control operates only when frequency stability is established, preventing the problem of phase control interfering with frequency convergence while minimizing delay through continuous monitoring and immediate activation upon convergence.
Data Source
AI summary
A PFD outputs a detection signal based on a phase difference or a frequency difference between a reference signal and a feedback signal, a charge pump circuit outputs a pulse signal based on the detection signal, and a loop filter outputs a control voltage based on the pulse signal. A VCO includes a ring oscillator where a plurality of delay element units, which include a plurality of delay elements (for example, inverter circuits) connected in parallel, are connected in series in a ring, controls the frequency of the output signal of the ring oscillator based on the control voltage, and controls the phase of the output signal of the ring oscillator by controlling the active number of delay elements, out of the plurality of delay elements, based on the detection signal. A frequency divider circuit generates and outputs a feedback signal by dividing the frequency of the output signal.