GPS Signal Synchronization via Code Word Phase Alignment
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Solution Overview
Problem
Existing GPS receivers face inefficiencies in power consumption due to Doppler shift and code phase changes, leading to inaccurate positioning and high power usage, especially when the receiver is in motion or with weak signal strength.
Innovation Solution
A method and device for synchronizing coded channels by determining time-shifts between periodic signals and code words, dividing them into parts, and forming new code words to align phases, allowing for RF parts to be shut down for longer periods while maintaining signal detection, utilizing a software GPS receiver with a mixer operating at 0 Hz IF frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If the RF section is powered down to save energy, then power consumption is reduced, but signal acquisition and tracking become inaccurate due to Doppler shift and code phase changes
Solution Approach 1:
The system performs preliminary actions by storing multiple pre-generated code words in memory before the RF section is powered down. These code words are generated in advance with different time-shifts to compensate for expected Doppler shifts and code phase changes. When the RF section is reactivated, the system can quickly select and apply the appropriate pre-generated code word without needing to regenerate codes, thus maintaining positioning accuracy while enabling power savings.
Solution Approach 2:
The system dynamically adapts by using a software-based code generator that can rapidly produce code words with different time-shifts based on the receiver's motion state. The system adjusts the code generation strategy according to whether the receiver is moving or stationary, and selects appropriate code words from memory based on detected signal conditions, enabling flexible response to changing environmental conditions while maintaining accuracy.
2Speed
If the integration period is shortened to enable quicker code acquisition, then acquisition speed is improved, but correlation power decreases making signal detection more difficult
Solution Approach 1:
The system performs preliminary correlation operations by pre-generating multiple code words with different time-shifts and storing them in memory before actual signal processing. This preliminary preparation allows the system to quickly search through multiple code hypotheses simultaneously when the RF section is active, achieving fast code acquisition without sacrificing detection reliability because the pre-generated codes are based on expected Doppler shifts and code phases.
Solution Approach 2:
The system segments the code acquisition process by dividing the search space into multiple discrete code words with different time-shifts. Instead of searching continuously, the system tests multiple segmented code hypotheses in parallel by selecting appropriate pre-generated code words from memory, thereby speeding up acquisition while maintaining reliable detection through multiple simultaneous hypotheses.
3Measurement precision
If the receiver samples signals continuously to maintain accurate positioning, then positioning accuracy is maintained, but power consumption increases
Solution Approach 1:
The system implements periodic sampling instead of continuous sampling. The RF section is powered down during intervals between position fixes and reactivated only when new position data is needed. By using pre-generated code words stored in memory that account for expected Doppler shifts and code phase changes during the idle period, the system can quickly reacquire signals and maintain positioning accuracy while consuming significantly less power during the periodic idle intervals.
4Reliability
If the duty cycle is increased to improve signal strength for weak signals, then signal detection reliability is improved, but power consumption increases
Solution Approach 1:
The system performs preliminary generation and storage of multiple code words with different time-shifts in memory before the RF section is activated. For weak signals, the system can rapidly test multiple pre-generated code hypotheses in parallel immediately upon activation, improving detection reliability without needing to maintain a high duty cycle. The pre-prepared codes enable quick identification of the correct signal even with limited active sampling time.
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 enables significant power savings, up to 95% reduction in RF part usage, by ensuring reliable signal acquisition with minimal sampling, even with weak signals, and maintaining accurate positioning.
Implementation Method 1
the method comprises a step of mixing said periodic signal to IF frequency. In an embodiment of the invention said IF frequency is substantially 0 Hz
Implementation Method 2
All these methods rely on the effect of autocorrelation, wherein a GNSS receiver will generate exact replicas of a carrier frequency and pseudo-random noise code and multiply these replicas with the incoming signal. If the carrier frequency and code phase of the generated signals match the ones in the incoming signal, it will produce maximum correlation power
Implementation Method 3
All the satellites transmit at the same carrier frequency, but due to the high velocity of the satellites the signals will experience a Doppler shift in frequency before reaching the GNSS receiver. The Doppler shift can be several kHz in magnitude
Data Source
Figure 1~4
Figure 5
AI summary
First aspect of the present invention is a code editing method for synchronizing coded channels in a periodic signal. The method comprises steps of determining time-shifts between said periodic signal and each code word in a set of code words, dividing the code words into a certain first part and to a certain second part, and forming new code words by interchanging said first parts and said second parts of each code word based on the determined time-shifts so that said new code words are arranged to have essentially the same phase as the corresponding channels in the periodic signal.