Temperature-Compensated Clock Correction for Faster GPS First Fix
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Solution Overview
Problem
Existing cellular devices with satellite positioning capabilities face accuracy issues when timing signals from cellular networks are unavailable, leading to prolonged Time To First Fix (TTFF) during GPS acquisitions.
Innovation Solution
A wireless communications device with a temperature-compensated clock circuit and a clock correction method that uses historical correction values to maintain accurate clock signals, even without network timing signals, by integrating a temperature sensor and processors to self-calibrate and store voltage correction values for the voltage-controlled temperature-compensated crystal oscillator (VCTCXO).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the device uses cellular network timing signals to calibrate the clock, then GPS clock accuracy is improved, but the device cannot maintain accurate timing when cellular network signals are unavailable
Solution Approach 1:
The device performs preliminary calibration of the VCTCXO using cellular network timing signals when available, storing the correction values in memory for later use. This preliminary action ensures that accurate correction data is prepared in advance, allowing the GPS clock to maintain high accuracy even when network signals become unavailable.
Solution Approach 2:
The system creates a copy of the correction values derived from the cellular network timing signals and stores them in memory. These copied correction values are then applied to the GPS clock independently, allowing the GPS timing to replicate the accuracy of the cellular-calibrated clock without requiring continuous network connectivity.
2Loss of time
If the device continuously monitors and corrects clock frequency using cellular signals, then Time To First Fix is reduced, but energy consumption increases
Solution Approach 1:
The device performs frequency calibration and correction value generation in advance when cellular signals are available, storing these correction values for later use. This preliminary calibration reduces the need for continuous monitoring and correction operations, thereby reducing energy consumption while maintaining fast TTFF performance when needed.
Solution Approach 2:
The system uses the stored correction values to autonomously adjust the GPS clock frequency without requiring continuous external reference signals. The GPS receiver can self-correct its timing using the pre-stored calibration data, reducing the need for continuous active monitoring and lowering power consumption during GPS operations.
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 ensures faster Time To First Fix (TTFF) and improved GPS accuracy by autonomously correcting the clock signal based on stored historical data, even when cellular network timing signals are unavailable, enhancing satellite positioning performance.
Implementation Method 1
a voltage-controlled temperature-compensated crystal oscillator (VCTCXO) for generating a clock signal
Implementation Method 2
voltage-controlled temperature-compensated crystal oscillator (VCTCXO) for generating a clock signal
Implementation Method 3
integrating a temperature sensor and processors to self-calibrate and store voltage correction values
Data Source
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AI summary
A wireless communications device may include a portable housing and a temperature-compensated clock circuit carried by the portable housing. The device may further include a wireless receiver carried by the portable housing for receiving timing signals, when available, from a wireless network, and a satellite positioning clock circuit carried by the portable housing. A clock correction circuit may be carried by the portable housing for correcting the temperature-compensated clock circuit based upon timing signals from the wireless network when available, and storing historical correction values for corresponding temperatures. The clock correction circuit may also correct the temperature-compensated clock circuit based upon the stored historical correction values when timing signals are unavailable from the wireless network, and correct the satellite positioning clock based upon the temperature-compensated clock circuit.