PLL Oscillator Lookup-Table Calibration for Frequency Accuracy
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Solution Overview
Problem
Existing phase-locked loop circuits struggle to produce frequency signals with high accuracy, particularly in applications like range sensing using radar technology, where deviations in frequency-modulated signals significantly affect distance measurements.
Innovation Solution
A method of controlling a frequency-modulated oscillator in a phase-locked loop circuit, utilizing a bank of capacitors, where capacitors are switched to change output frequencies, and frequency information is determined and written to a look-up table for precise frequency control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a frequency-modulated oscillator is used in a phase-locked loop circuit, then the oscillator can generate frequency signals for applications like range sensing, but frequency deviations and errors in the linearly frequency-modulated signals occur, which significantly affect measurement accuracy
Solution Approach 1:
The patent applies preliminary action by performing calibration before normal operation. During calibration mode, the system pre-determines frequency information for each capacitor state and stores it in a look-up table. This preliminary characterization of the oscillator's frequency behavior allows the system to compensate for deviations and errors during actual range sensing operations, thereby improving measurement accuracy without sacrificing frequency signal generation capability
Solution Approach 2:
The patent implements feedback by using the determined frequency information from calibration to adjust and correct frequency deviations during operation. The look-up table stores correction data that is referenced during normal operation to compensate for oscillator inaccuracies, creating a feedback mechanism that continuously improves measurement precision while maintaining the oscillator's productivity
2Adaptability or versatility
If capacitors are switched to change output frequency, then frequency modulation is achieved, but frequency deviations and nonlinearities occur that reduce signal accuracy
Solution Approach 1:
The system performs preliminary calibration by switching through all capacitor states and measuring the actual frequency output for each state. This preliminary action characterizes the nonlinear frequency behavior of the capacitor bank, allowing the look-up table to store correction factors that compensate for manufacturing tolerances and nonlinearities, thereby maintaining frequency signal accuracy across the full tuning range
Solution Approach 2:
The patent changes parameters by storing multiple frequency information values in the look-up table corresponding to different capacitor states. By referencing the appropriate pre-measured frequency information based on the current capacitor configuration, the system compensates for parameter variations and nonlinearities, maintaining accurate frequency control while preserving the adaptability to tune across a wide frequency range
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This solution enables the generation of frequency signals with high accuracy, improving the precision of distance measurements in radar applications by effectively managing frequency deviations and nonlinearities.
Implementation Method 1
the oscillator comprises a bank of capacitors... switching a capacitor of the bank of capacitors to change an output frequency of an output signal of the oscillator
Data Source
AI summary
A method of controlling a frequency-modulated oscillator 110 of a phase-locked loop circuit 100 is described, wherein the oscillator 110 comprises a bank of capacitors 413. The method comprises the steps of (i) switching a capacitor 414 of the bank of capacitors 413 to change an output frequency 1050 of an output signal 112 of the oscillator 110 from a first frequency 1051 to a second frequency 1052, (ii) determining a frequency information associated with the capacitor 414 and based on at least one of the first frequency 1051 and the second frequency 1052; and (iii) writing the frequency information to a look-up table 224, 225, 226 stored in a control unit 120 of the oscillator 110. A corresponding frequency-modulated oscillator 110 and phase-locked loop circuit 100 are also described.