GNSS Crystal Oscillator Calibration Using WLAN Temperature Feedback
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Solution Overview
Problem
The frequency of crystal oscillators (XOs) in GNSS receivers is affected by temperature variations, leading to instability and increased signal acquisition times, which hampers the sensitivity and accuracy of wireless devices in indoor environments.
Innovation Solution
A wireless node, such as an access point (AP) in a WLAN, monitors the temperature of an XO and adjusts the carrier/sampling frequency based on temperature changes, utilizing thermal sensors from neighboring stations to calibrate the XO's frequency-temperature response, enabling improved stability and reduced acquisition times.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the frequency of crystal oscillators is used in GNSS receivers, then signal acquisition and decoding can be performed, but temperature variations cause frequency instability and increased acquisition times
Solution Approach 1:
The patent implements a feedback mechanism where the system continuously monitors the temperature of the crystal oscillator using a thermal sensor, compares the actual temperature against expected temperature-frequency characteristics, and applies frequency correction values to compensate for deviations. This closed-loop feedback system maintains frequency stability despite temperature variations, resolving the contradiction between reliability and acquisition time.
Solution Approach 2:
The system dynamically adjusts the oscillator frequency parameter based on temperature measurements. By changing the frequency parameter in response to temperature variations (using correction values derived from temperature-frequency characteristic data), the system maintains accurate signal processing while accounting for environmental conditions, thus preventing increased acquisition times.
2Reliability
If thermal sensors and calibration procedures are added to compensate for temperature effects, then frequency stability improves, but device complexity increases
Solution Approach 1:
The patent makes the crystal oscillator serve multiple functions: it provides the primary frequency reference for GNSS signal processing and simultaneously acts as a temperature sensor through its inherent temperature-frequency relationship. By measuring the oscillator's frequency drift, the system derives temperature information without requiring separate sensing mechanisms, thereby improving frequency stability while minimizing additional device complexity.
Solution Approach 2:
The crystal oscillator's natural temperature-dependent frequency drift is utilized as a self-diagnostic feature. Instead of requiring external temperature sensors and complex calibration hardware, the system uses the oscillator's own frequency variations to infer temperature and apply self-correction through stored calibration data, achieving frequency stability compensation with minimal added complexity.
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
The calibration method enhances the stability and sensitivity of GNSS receivers by compensating for temperature-induced frequency variations, reducing signal acquisition times and improving positioning accuracy.
Implementation Method 1
A thermal sensor disposed proximate to the XO may be used to determine the temperature of the XO
Data Source
AI summary
Techniques are provided for calibrating a crystal oscillator (XOs) in a global navigation satellite system (GNSS) receiver. An example method for generating XO calibration information includes receiving radio frequency signals from a wireless node, wherein the radio frequency signals include an indication of oscillator temperature information, determining a frequency offset value based at least in part on the radio frequency signals, determining a local oscillator temperature value, determining a frequency correction value based at least in part on the local oscillator temperature value, the frequency offset value, and the indication of oscillator temperature information, and transmitting a calibration report to the wireless node.