PLL Loop Gain Control for Stable Wideband Phase Noise Suppression
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional PLL circuits face challenges in maintaining a stable phase noise suppression characteristic due to variations in temperature and individual differences in device characteristics, especially when operating in a wide frequency band.
Innovation Solution
The PLL circuit incorporates a loop gain varying mechanism and response characteristic adjustment system, utilizing registers and multipliers to set optimal parameters based on device state and use conditions, with a temperature sensor and correction value memory to compensate for temperature variations and individual differences, ensuring stable phase noise suppression across a wide frequency band.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional PLL circuit is used, then the basic frequency synthesis function is achieved, but the phase noise suppression characteristic deteriorates due to temperature variation and device individual differences
Solution Approach 1:
The patent implements dynamic adjustment of the loop gain by varying the gain coefficient in the loop filter based on detected temperature. This allows the PLL circuit to adapt its characteristics in real-time to compensate for temperature-induced variations, maintaining stable phase noise suppression across different operating conditions.
Solution Approach 2:
The patent changes the loop gain parameter dynamically according to temperature conditions. By adjusting the gain coefficient of the loop filter based on temperature detection, the system optimizes the loop gain to maintain consistent phase noise suppression characteristics despite environmental variations.
2Reliability
If a conventional PLL circuit is used, then the basic frequency synthesis function is achieved, but the phase noise suppression characteristic varies due to individual device differences
Solution Approach 1:
The patent employs feedback mechanisms where the actual phase noise characteristic is measured and used to adjust the loop gain. This closed-loop control compensates for individual device variations by continuously optimizing the gain coefficient based on actual performance measurements.
Solution Approach 2:
The patent performs preliminary measurement of the phase noise characteristic during device initialization or calibration. Based on these measurements, the optimal gain coefficient is determined in advance and stored, allowing the device to compensate for individual differences without requiring complex real-time adjustments during operation.
3Reliability
If the loop gain is optimized for one frequency band, then phase noise suppression is improved in that band, but performance deteriorates in other frequency bands
Solution Approach 1:
The patent dynamically adjusts the loop gain coefficient based on the operating frequency band. By detecting the current frequency and selecting an appropriate gain coefficient, the system optimizes phase noise suppression for the active band while maintaining acceptable performance across other bands.
Solution Approach 2:
The patent applies different gain coefficients tailored to specific frequency bands. Each band has its own optimized gain value stored in memory, allowing the system to achieve local optimization for each band rather than using a compromise value that would work suboptimally across all bands.
Data Source
AI summary
A PLL circuit which can absorb variation of phase noise characteristic due to temperature and individual difference and has a phase noise suppression characteristic stable in a wide frequency band is provided. The PLL circuit comprises, at the succeeding stage, a first register for storing a first parameter for controlling the loop gain, a first multiplier for multiplying the output of the phase comparator by a first parameter, a second register for storing a second parameter for controlling the response characteristic, a second multiplier for multiplying the output of the first multiplier by a second parameter, and a CPU for setting optimum parameters in the first and second registers depending on the use frequency band, the ambient temperature, and the device individual difference. By controlling the loop gain and the response characteristic to optimum values, a good suppression characteristic in a wide frequency band is achieved.