PLL Bandwidth Calibration Using Offset-Compensated Phase Steps
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Solution Overview
Problem
Existing phase-locked loop (PLL) frequency synthesizers face challenges in accurately measuring and controlling their parameters, particularly the natural frequency and damping coefficient, due to variations caused by temperature, supply voltage, and manufacturing tolerances, as well as phase offsets and nonlinearities, which lead to significant errors in dynamic analysis and calibration.
Innovation Solution
The method involves temporarily shutting off the proportional path in the PLL, introducing phase steps of opposite polarities, and measuring the time-to-zero crossing to accurately determine the PLL's natural frequency and damping coefficient, allowing for adjustments to achieve target values and compensate for phase offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional PLL parameter measurement methods are used, then the measurement process is simple, but the measurement precision is poor due to phase offsets and nonlinearities
Solution Approach 1:
The patent applies preliminary action by performing offset compensation before the actual parameter measurement. The system first measures and compensates for phase offsets using phase step sequences, then proceeds with accurate parameter measurement. This preliminary offset characterization enables subsequent measurements to be free from offset errors, resolving the contradiction between measurement precision and process complexity.
Solution Approach 2:
The patent replaces traditional mechanical/probe-based measurement methods with signal processing-based measurement. Instead of physical probing that introduces offsets, the system uses injected phase step sequences and digital signal processing to measure parameters, eliminating the source of measurement errors while maintaining procedural simplicity.
2Reliability
If phase offsets are present in the PLL, then the PLL can operate normally, but the dynamic analysis accuracy deteriorates due to errors in parameter measurement
Solution Approach 1:
The patent converts the harmful effect of phase offsets into a beneficial measurement tool. By intentionally injecting known phase step sequences and measuring the PLL's response, the system characterizes and compensates for offsets. The previously harmful offsets become part of the measurement process, enabling accurate dynamic analysis while maintaining normal PLL operation.
Solution Approach 2:
The patent implements feedback by using the measured phase offset information to correct subsequent parameter measurements. The system continuously monitors the PLL response to phase steps, calculates offset values, and applies compensation to maintain accurate dynamic analysis, creating a closed-loop measurement system that eliminates offset errors.
3Adaptability or versatility
If the PLL operates under varying temperature and voltage conditions, then the PLL can adapt to different environments, but the parameter stability deteriorates due to component variations
Solution Approach 1:
The patent applies parameter changes by measuring and compensating for PLL parameter variations under different operating conditions. The system characterizes how natural frequency and damping coefficient change with temperature and voltage, then applies corrections to maintain stable dynamic analysis results despite environmental variations and component tolerances.
Data Source
AI summary
A method and system for compensating for offsets when measuring parameters of a phase-locked loop (PLL). In one embodiment, a proportional path in the PLL is temporarily shut off, a measurement is made of a real time-to-zero crossing in the PLL to measure a defined parameter of the PLL, the proportional path is switched on, and the defined loop parameter is adjusted based on this measurement. In one embodiment, the real time-to-zero crossing is measured after introducing a phase step into the PLL between a reference signal and an output signal of the PLL. In an embodiment, two phase steps, having opposite polarities, are successively introduced into the PLL, and the time-to-crossing measurements resulting from these two phase steps may be averaged, and this average is used to determine a loop parameter.