Satellite Receiver Clock Stabilization for Weak Signal Acquisition
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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 indoors, due to limited sensitivity and signal attenuation.
Innovation Solution
A device with a SPS receiver and wireless receiver uses long integration of SPS signals with a stable clock signal sourced from a wireless communication base station or femtocell, combined with predicted SPS data for coherent or non-coherent integration, and motion sensors to compensate for Doppler errors, enhancing signal acquisition and tracking.
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 requirements for stable external clock sources and complex integration processing
Solution Approach 1:
The patent introduces an external clock source (such as a base station clock or femtocell clock) as an intermediary to provide highly stable timing reference for the SPS receiver. This external clock acts as a mediator between the weak SPS signals and the integration processing, enabling long coherent integration without requiring the mobile device to generate its own stable clock, thus improving signal sensitivity while managing device complexity by offloading the timing stability requirement to the network infrastructure.
2Stability of the object's composition
If external clock signal from wireless communication base station is used to produce stable internal clock signal, then integration stability is improved, but adaptability decreases in environments where external clock sources are unavailable
Solution Approach 1:
The patent implements a dynamic clock sourcing strategy where the system can switch between using an external clock source (when available) and relying on the device's internal oscillator (when external sources are unavailable). This dynamic adaptability allows the system to maintain operation across different environments - using the external clock for high-stability integration when possible, and falling back to internal timing when necessary, thus balancing integration stability with environmental adaptability.
3Measurement precision
If predicted SPS data is received from external source to perform coherent integration, then measurement precision is improved, but loss of information increases due to reliance on external assistance data
Solution Approach 1:
The patent employs preliminary action by receiving and storing predicted SPS data (such as satellite ephemeris and almanac information) from external sources in advance of the actual positioning measurement. This pre-acquired information is then used during coherent integration to improve measurement precision, especially in weak signal conditions. The system performs the useful action of data acquisition beforehand, allowing the integration process to proceed with enhanced accuracy without requiring real-time external assistance during the critical measurement phase.
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 allows for stable and accurate position determination in challenging environments by improving signal sensitivity and integration duration, enabling effective navigation even in obstructed areas.
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.