Multiphase Oscillator PLL for Higher Phase Resolution
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Solution Overview
Problem
Conventional phase-locked loops often suffer from low resolution in phase difference detection, leading to unwanted effects like jitter due to low frequency components, particularly in digital phase-locked loops.
Innovation Solution
A circuit comprising a multiphase oscillator generating multiple output signals with the same frequency but different phase offsets, a feedback value generator, and a reference value generator, along with a loop filter to control the oscillator based on feedback and reference values, enhancing phase resolution by utilizing multiple phase outputs for alignment with a reference clock.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional phase-locked loops are used with single-phase output, then device complexity is reduced, but phase resolution deteriorates causing jitter
Solution Approach 1:
The oscillator is divided into multiple phase outputs (e.g., 4 phases) instead of a single phase. Each phase output provides a distinct timing reference point, allowing the phase detector to measure phase differences with higher resolution by selecting appropriate phase transitions, thereby reducing jitter without significantly increasing overall system complexity.
Solution Approach 2:
The invention adds a phase dimension to the output signals by generating multiple phase-shifted versions of the same frequency signal. This dimensional expansion from single-phase to multi-phase allows the system to achieve higher measurement precision in phase detection by utilizing multiple reference points across different phase angles.
2Device complexity
If low resolution phase difference detection is used, then device complexity is reduced, but unwanted jitter and low frequency components are generated
Solution Approach 1:
The phase detector continuously monitors the phase difference between the reference signal and the divided feedback signal from the voltage controlled oscillator. This feedback mechanism allows real-time adjustment of the oscillator frequency and phase, enabling the system to suppress jitter and eliminate low frequency components by correcting phase errors as they occur, thereby reducing harmful effects.
3Measurement precision
If multiple phase outputs are generated, then phase resolution is improved, but device complexity increases
Solution Approach 1:
The multi-phase oscillator serves multiple functions simultaneously: it generates the primary clock signal, provides multiple phase references for high-resolution detection, and enables frequency division. This multi-functionality allows the system to achieve high phase resolution without proportionally increasing device complexity, as the same hardware structure supports multiple operational requirements.
Data Source
AI summary
In an embodiment, a circuit is provided comprising a multi-phase oscillator configured to output a plurality of output signals having the same frequency and different phase offsets. A feedback value is generated based on at least two of said output signals. A reference value is generated based on a reference clock and a predetermined value. The reference value and the feedback value are combined.