Adaptive PLL Coefficient Control for Video Sync Jitter Reduction
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Solution Overview
Problem
Conventional PLL controllers require external control of coefficients to manage phase-locked loops, which is inadequate for non-standardized video signals, leading to jittered video images due to frequency errors and noise interference.
Innovation Solution
A PLL controller that automatically detects phase errors and adjusts a multiplier coefficient based on the error state, allowing for adaptive tracking rate control within the phase-locked loop, independent of signal type, using error amount detectors and coefficient selectors to select suitable gains for phase-locked loop control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the phase-locked loop quickly tracks the errors in the lines of the signal, then video images with less jitter are attained, but the influence from false detection of the period of each line increases
Solution Approach 1:
The patent applies dynamics by making the tracking rate of the phase-locked loop adjustable and adaptive. The controller dynamically changes the tracking rate based on the detected signal type, allowing the system to optimize between tracking speed and reliability for different video signal conditions.
Solution Approach 2:
The patent changes the tracking rate parameter of the phase-locked loop based on the detected signal characteristics. By adjusting this key parameter according to whether the signal is from a video cassette player or television broadcast, the system resolves the contradiction between fast tracking and reliable period detection.
2Reliability
If the phase-locked loop slowly tracks the errors in the lines of the signal, then the influence from false detection is reduced, but video images exhibit more jitter
Solution Approach 1:
The system dynamically adjusts the tracking rate based on signal type detection. For television broadcast signals with potential false detections, the tracking rate is reduced to improve reliability, while for video cassette player signals, the tracking rate is increased to reduce jitter.
Solution Approach 2:
The tracking rate parameter is changed according to the detected signal characteristics. This parameter adjustment allows the system to optimize performance for different signal sources, resolving the trade-off between tracking accuracy and video image quality.
3Adaptability or versatility
If a fixed coefficient is used in the phase-locked loop, then the device complexity is reduced, but the system cannot adapt to non-standardized video signals
Solution Approach 1:
The PLL controller performs self-service by automatically detecting the signal type and selecting the appropriate tracking rate and coefficient without external intervention. This self-adaptive capability provides versatility for different signal types while keeping the user interface simple.
Solution Approach 2:
The system uses feedback from phase error detection to automatically adjust the tracking rate and coefficient. This feedback mechanism enables the system to adapt to non-standardized signals while maintaining manageable complexity through automated control.
Data Source
AI summary
A PLL controller for controlling the tracking rate of a phase-locked loop (PLL), in particular, controlling coefficients to be input to a device such as a multiplier of the phase-locked loop. A PLL controller receives a phase error between a horizontal sync signal in a video signal and a reference signal. Then an error amount detector measures the phase error using the N thresholds to output a control signal indicating any of N+1 levels. A coefficient selector outputs one of the N+1 gains as a coefficient signal, the one gain corresponding to the level indicated by the control signal, so that the tracking rate of the phase-locked loop is controlled in response to the input video signal, and thus a high-quality video image with less jitter can be provided.