PLL Reference Oscillator Drift Compensation for Spur Suppression
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Solution Overview
Problem
Conventional phase locked loops (PLLs) in cellular phones experience performance degradation due to drifting oscillation signals from free-running oscillators, leading to spur generation that affects communication quality.
Innovation Solution
The implementation of a controller module within the PLL that adjusts the frequency and phase of the reference signal to compensate for drift, ensuring it remains proportional to the target signal, thereby eliminating spurs and maintaining communication device performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a free running oscillator is used to provide the reference signal to the PLL, then the device complexity is reduced, but the reliability deteriorates due to frequency drift causing spur generation
Solution Approach 1:
The patent implements a feedback mechanism where the PLL detects frequency drift in the reference signal and generates correction signals to adjust the oscillator frequency, thereby eliminating spurs while maintaining system simplicity
Solution Approach 2:
The patent dynamically adjusts the oscillator frequency parameter in response to detected drift, changing the operating parameters to compensate for environmental variations and maintain signal stability
2Ease of operation
If the oscillation frequency is allowed to drift with temperature and time, then the ease of operation is improved, but the manufacturing precision deteriorates due to spur generation degrading performance
Solution Approach 1:
The PLL continuously monitors the reference signal frequency and provides feedback control to maintain accurate operation despite environmental variations, preventing spur generation while requiring minimal user intervention
3Adaptability or versatility
If the PLL output is directly related to a drifting oscillation signal, then the adaptability is improved, but the object-affected harmful factors increase due to spur generation
Solution Approach 1:
The feedback control mechanism allows the PLL to adapt to frequency drift while actively suppressing harmful spurs through corrective action, maintaining both adaptability and signal quality
Solution Approach 2:
The patent converts the harmful effect of frequency drift into a useful signal for the feedback mechanism to detect and correct, transforming the potential harm into an opportunity for automatic calibration and improvement
Data Source
AI summary
Embodiments of this disclosure include methods in which spurs generated by the drifting of an oscillation frequency of an oscillation signal provided by a free-running oscillator may be minimized and/or eliminated from an output signal of a phase locked loop (PLL). Methods include adjusting the free-running oscillator to prevent the oscillation frequency from drifting so that the spurs are eliminated. Performance data generated when the communications device engages a communications channel that is known not to generate spurs is compared to performance data generated when the communications device engages a desired communications channel. The free-running oscillator is adjusted until the two types of performance data are matched. Other methods include adjusting the dithering module of the PLL to prevent the oscillation frequency from drifting so that the spurs are eliminated.