Satellite Receiver External Clock Synchronization
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Solution Overview
Problem
Current satellite positioning system (SPS) receivers face challenges in accurately determining position in environments with blockages or weak signals, such as indoor settings, due to limited sensitivity and stability in receiving and interpreting weak satellite signals.
Innovation Solution
A device with a satellite positioning system receiver and a wireless receiver uses long integration of SPS signals with a stable clock signal sourced from an external clock, such as a wireless communication base station, and incorporates motion sensors to compensate for Doppler errors, enabling coherent or non-coherent integration to improve signal sensitivity and accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If long integration over multiple navigation data bits is used to acquire weak SPS signals, then signal sensitivity is improved, but device complexity increases due to the need for stable external clock synchronization and motion compensation mechanisms
Solution Approach 1:
An external clock signal from a highly stable source (wireless base station, NTP/PTP server, or femtocell) serves as an intermediary to provide timing reference for the integration process, enabling long integration times without requiring the receiver's internal oscillator to be sufficiently stable
Solution Approach 2:
Motion sensors provide feedback about device movement, which is used to compensate for Doppler errors in the external clock signal and adjust the integration process accordingly, maintaining measurement precision despite device motion
2Stability of the object's composition
If external clock signal from wireless base station is used for long integration, then clock stability is improved, but loss of time increases due to need to acquire and synchronize with external clock source
Solution Approach 1:
The receiver acquires and synchronizes with the external clock signal in advance before attempting to integrate weak SPS signals, ensuring that the timing reference is already established and reducing the time needed for signal acquisition
Solution Approach 2:
The external clock infrastructure (wireless base stations, NTP/PTP servers, femtocells) serves multiple purposes: providing timing for SPS signal integration, enabling network synchronization, and offering a stable frequency reference for Doppler compensation
3Measurement precision
If motion sensor is used to compensate for Doppler errors, then measurement precision is improved, but use of energy increases due to continuous motion monitoring and compensation calculations
Solution Approach 1:
Motion compensation is applied selectively based on detected motion levels - full compensation when motion is detected, reduced or no compensation when the device is stationary, optimizing energy consumption while maintaining measurement precision when needed
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 approach enhances the ability to track and determine position in environments with compromised SPS signals, providing stable and accurate navigation data even in obstructed areas by extending integration time and improving signal sensitivity.
Implementation Method 1
a motion sensor may be used to determine if there is motion relative to the external clock source or to compensate for Doppler errors in the external clock signal due to motion
Data Source
AI summary
An attenuated satellite positioning system (SPS) signal is acquired using long integration over multiple navigation data bits. To produce a stable internal clock signal to perform the long integration, an external clock signal is received from a highly stable source, such as a wireless communication base station or a nearby femtocell. An internal oscillator is driven at a desired frequency that is aligned with the scaled frequency of the external clock signal to produce the stable internal clock signal. The SPS signal is received and integrated for an extended period using the internal clock signal. Predicted SPS data may be received from an external source and used to perform coherent integration. Alternatively, non-coherent integration may be performed. Additionally, a motion sensor may be used to determine if there is motion relative to the external clock source or to compensate for Doppler errors in the external clock signal due to motion.