Realigned Oscillator Local Phase Detection for Low-Jitter PLLs
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Solution Overview
Problem
Phase-locked loop (PLL) devices experience disturbances and increased jitter due to time delays in detecting and transmitting phase/frequency information, leading to misalignment, reference spurs, and potential PLL unlock.
Innovation Solution
The solution involves injecting an edge of a reference signal into a controlled oscillator, such as a digitally controlled oscillator (DCO) or voltage controlled oscillator (VCO), at specific points within the oscillator circuit, using multiplexers to replace corresponding edges of the oscillation signal, thereby reducing jitter and phase noise through local phase measurement and realignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If phase/frequency detection is performed using external circuits, then phase information can be obtained, but time delays cause misalignment and increased jitter
Solution Approach 1:
The phase detector is merged with the oscillator circuit by placing it at the injection point within the oscillator. This integration eliminates external transmission paths and reduces time delays in detecting and transmitting phase information, directly resolving the contradiction between obtaining phase information and avoiding detection delays.
Solution Approach 2:
The injection point within the oscillator serves as an intermediary location where the reference signal is introduced and phase detection is performed. This intermediary position allows local measurement of phase difference without the time delays associated with external detection circuits, maintaining measurement precision while minimizing time loss.
2Reliability
If reference signal is injected into the oscillator, then jitter and phase noise are reduced, but circuit complexity increases
Solution Approach 1:
The injection point is designed to serve multiple functions: it is used both for injecting the reference signal to reduce jitter and phase noise, and for performing local phase detection. This multi-functionality improves oscillator stability without requiring separate dedicated circuits, thereby limiting the increase in circuit complexity.
Solution Approach 2:
The reference signal injection and phase detection functions are merged at the same location within the oscillator circuit. This consolidation achieves the reliability improvement from signal injection while avoiding the additional complexity that would result from separate injection and detection circuits.
3Loss of time
If phase detection is performed locally within the oscillator, then time delays are minimized, but the oscillator structure becomes more complex
Solution Approach 1:
The phase detection circuit is merged with the oscillator structure by placing it at the injection point. This integration minimizes time delays by eliminating external transmission paths while the merging approach itself limits the increase in internal structure complexity compared to adding completely separate detection circuits.
Data Source
AI summary
Representative implementations of devices and techniques provide reduced jitter and local phase detection for a controlled oscillator. An edge of a reference signal is injected at a point within the oscillator, and replaces an edge of the generated oscillation signal at the injection point. A phase difference of the injected reference signal and the oscillation signal is measured locally and is used to tune the oscillator.