Adaptive PLL Loop Control for Stable Wideband Phase Noise
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Solution Overview
Problem
Conventional PLL circuits face challenges in maintaining a stable phase noise suppression characteristic due to temperature variations and individual differences in device characteristics, especially when operating in a wide frequency band.
Innovation Solution
The PLL circuit incorporates a first register and first multiplier to adjust the loop gain, and a second register and second multiplier to adjust the damping factor, with a CPU setting optimal parameters based on the use frequency band, ambient temperature, and device differences, using temperature tables to correct for individual differences and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional PLL circuit parameters are used, then the circuit operates at standard conditions, but the phase noise suppression characteristic deteriorates due to temperature variation and individual device differences
Solution Approach 1:
The patent implements dynamic parameter adjustment by introducing controllable switches (first and second switches) that connect or disconnect capacitor banks based on temperature and device characteristics. This transforms the static filter configuration into a dynamic system that adapts to varying conditions, maintaining optimal phase noise suppression across different operating scenarios.
Solution Approach 2:
The patent changes physical parameters of the loop filter by selectively connecting different capacitor values (C1-C4) to the integration circuit based on temperature and device characteristics. This parameter adjustment modifies the loop filter transfer function, enabling optimization of phase noise suppression for different operating conditions without changing the fundamental circuit architecture.
2Reliability
If fixed loop filter parameters are used, then the circuit design is simple, but the phase noise suppression deteriorates in wide frequency bands
Solution Approach 1:
The patent introduces dynamic control mechanisms (switches controlled by temperature sensors and device identification circuits) that automatically reconfigure the loop filter parameters based on operating conditions. This dynamic approach enables a single filter structure to serve multiple frequency bands and temperature ranges, avoiding the need for entirely separate filter designs for each condition.
Solution Approach 2:
The loop filter is segmented into modular capacitor banks (C1-C4) that can be independently connected or disconnected. This segmentation allows flexible combination of different capacitance values to optimize performance across wide frequency bands and temperature ranges, while maintaining a compact overall structure that doesn't significantly increase device complexity.
3Reliability
If temperature compensation is added to correct device variations, then the phase noise suppression improves, but the circuit complexity increases
Solution Approach 1:
The patent implements self-service temperature compensation where the temperature sensor and control logic automatically detect temperature changes and device characteristics, then autonomously adjust the loop filter parameters without external intervention. This self-adjusting mechanism eliminates the need for manual calibration or complex external compensation circuits, achieving temperature compensation with minimal added complexity.
Solution Approach 2:
The patent incorporates feedback mechanisms where temperature sensors continuously monitor operating conditions and feed this information to control switches that adjust filter parameters. This closed-loop feedback system automatically compensates for temperature variations and device differences, improving phase noise suppression while keeping the compensation circuit relatively simple through automated control.
Data Source
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AI summary
It has been difficult that conventional PLL circuits have a suppression characteristic of suppressing the phase noise which is free of variation due to temperature and individual difference and stable in a wide frequency band. The present invention provides 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. The PLL circuit comprises, at the succeeding stage, a first register (6) for storing a first parameter for controlling the loop gain, a first multiplier (7) for multiplying the output of the phase comparator (4) by a first parameter, a second register (12) for storing a second parameter for controlling the response characteristic, a second multiplier (13) for multiplying the output of the first multiplier by a second parameter, and a CPU (20) 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.