Temperature-Calibrated PLL Lock Range Without Varactor Noise Penalty
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Solution Overview
Problem
Phase lock loop (PLL) circuits face challenges in maintaining a locked output due to temperature fluctuations, as increasing the varactor size to enhance the lock range leads to increased amplitude-modulation to phase-modulation noise conversion, resulting in phase noise that impacts performance.
Innovation Solution
A PLL system with a dynamic lock range is achieved through a calibration process that uses a temperature sensor to adjust the control voltage of the voltage control oscillator based on a temperature reading, employing a calibration function defined by a slope with a numerator component corresponding to the control voltage range and a denominator component corresponding to ambient temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the size of the varactor is increased to increase the lock range, then the lock range is improved, but the amplitude-modulation to phase-modulation noise conversion increases, resulting in increased phase noise
Solution Approach 1:
The patent implements dynamic lock range adjustment by using a temperature sensor to detect junction temperature and a calibration circuit to adjust the control voltage of the VCO accordingly. This dynamic adaptation allows the PLL to maintain optimal performance across varying temperatures without requiring a larger varactor, thus avoiding the phase noise penalty while achieving temperature-dependent lock range optimization.
Solution Approach 2:
The patent changes the operating parameters of the PLL circuit by introducing temperature-based control voltage adjustment. The calibration circuit modifies the control voltage parameter based on temperature readings, effectively changing the VCO's frequency-temperature characteristics to compensate for drift and maintain lock stability without increasing varactor size, thereby avoiding increased phase noise.
2Reliability
If the varactor size is increased to maintain lock stability under temperature fluctuations, then the lock stability is improved, but the phase noise increases due to increased AM-to-PM conversion
Solution Approach 1:
The patent employs a feedback mechanism where a temperature sensor continuously monitors the junction temperature and feeds this information to a calibration circuit. The calibration circuit then adjusts the control voltage to compensate for temperature-induced frequency drift, maintaining lock stability without requiring a larger varactor. This feedback-based temperature compensation achieves reliability improvement while avoiding the phase noise penalty of increased varactor size.
Solution Approach 2:
The patent replaces the mechanical approach of increasing physical varactor size with an electronic control mechanism. Instead of using a larger varactor to broaden the lock range, the system uses temperature sensing and electronic control voltage adjustment to achieve the same stability goal, substituting physical dimension changes with electronic parameter control, thereby avoiding increased phase noise.
Data Source
AI summary
A phase look loop (PLL) device has a dynamic lock range that is based on a temperature measured during a calibration process. The PLL device includes a calibration circuit configured to receive a temperature reading corresponding to a junction temperature of the PLL device during the calibration process. Based on this temperature reading, the calibration circuit initiates a preset procedure that presets a control voltage of a voltage control oscillator in the PLL device. The preset procedure implements a calibration function defined by a slope with a numerator component and a denominator component. The numerator component corresponds to a range of the control voltage, whereas the denominator component corresponds to a range of ambient temperatures within which the PLL device operates.