Calibrating Low Frequency Oscillator Using High Frequency Reference
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Solution Overview
Problem
Conventional wireless communications systems face challenges in calibrating low frequency oscillator signals, leading to frequency offsets that degrade wireless connections or cause them to fail, especially in Bluetooth Low Energy devices that require precise frequency accuracy.
Innovation Solution
A method and device configuration that utilize a high frequency oscillator signal to calibrate a low frequency oscillator signal, generating a calibrated version of the low frequency clock signal for use in low energy mode, while the high frequency clock signal is disabled.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If a low frequency oscillator is used in low-energy mode, then power consumption is reduced, but frequency accuracy deteriorates leading to connection failures
Solution Approach 1:
The system performs frequency measurement and calibration of the low frequency oscillator during active mode before entering low-energy mode. This preliminary action ensures the oscillator is calibrated to the correct frequency, enabling accurate operation when the device transitions to power-saving mode without requiring the oscillator to maintain high accuracy continuously
Solution Approach 2:
The high frequency oscillator serves as an intermediary reference during calibration. By measuring the low frequency oscillator's output against the stable high frequency reference and calculating the frequency offset, the system can compensate for inaccuracies, allowing the use of less precise low frequency oscillators while maintaining connection accuracy
2Reliability
If frequency offset compensation is performed continuously, then connection accuracy is maintained, but power consumption increases
Solution Approach 1:
Instead of continuous calibration, the system performs frequency measurement and offset compensation periodically - specifically during active mode operation and before transitioning to low-energy mode. This periodic approach maintains connection accuracy when needed while minimizing power consumption by keeping the high frequency oscillator disabled during low-energy periods
3Measurement precision
If a high frequency oscillator is used continuously, then frequency accuracy is maintained, but power consumption increases
Solution Approach 1:
The system dynamically switches between different oscillator configurations based on operational mode. During active mode, both high and low frequency oscillators are enabled for calibration. During low-energy mode, only the calibrated low frequency oscillator remains active, dynamically adapting the system's frequency reference to match power and accuracy requirements of the current state
Data Source
AI summary
A method for operating a wireless communications device having a low energy mode of operation and a second mode of operation includes providing a first clock signal and a second clock signal in the second mode of operation. The first clock signal has a first frequency within a first frequency offset range. The second clock signal has a second frequency within a second frequency offset range. The first frequency is lower than the second frequency, and the first frequency offset range is greater than the second frequency offset range. The method includes generating a calibrated version of the first clock signal in the second mode of operation using a measurement of the first clock signal measured using a timer controlled by the second clock signal. The method includes using the calibrated version of the first clock signal in the low energy mode while the second clock signal is disabled.