GPS Receiver Doppler Shift Compensation for Weak Signal Sensitivity
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Solution Overview
Problem
In weak electric field environments, GPS satellite signals with Doppler shifts cause peak phase variations, making it difficult to distinguish the peak phase in correlation integrating processes, leading to blunted integrated correlation values and reduced receiving sensitivity.
Innovation Solution
A receiving device and method that estimate a data sequence shifted by a predetermined time to compensate for Doppler shifts, allowing for phase alignment during correlation operations, thereby preventing peak phase shifts and improving sensitivity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If correlation values are integrated over a predetermined period of time in weak electric field environments, then receiving sensitivity is improved, but peak phase shifts due to Doppler shift cause the integrated correlation value shape to become blunted, making it difficult to distinguish the peak phase
Solution Approach 1:
The invention applies preliminary action by estimating the peak phase shift amount due to Doppler shift before performing the correlation integration process. The receiver calculates the expected peak phase position based on Doppler frequency information, then uses this estimation to guide the correlation integration, ensuring that the integration is centered on the correct peak phase position rather than allowing the peak to drift during integration.
Solution Approach 2:
The invention changes the parameter of peak phase position estimation by incorporating Doppler shift compensation. Instead of treating the peak phase as a fixed or purely empirical value, the system dynamically adjusts the peak phase position parameter based on calculated Doppler shift amounts, thereby maintaining alignment between the correlation integration window and the actual signal peak despite frequency shifts.
2Ease of operation
If a correlation operation is performed on the received signal and replica code without phase compensation, then the process is simple, but the peak phase varies with time due to Doppler shift, causing the integrated correlation value to be blunted
Solution Approach 1:
The system performs preliminary estimation of the peak phase shift amount based on Doppler frequency before executing the correlation operation. This preliminary calculation allows the receiver to pre-position the correlation integration window at the expected peak location, avoiding the need for complex real-time phase tracking during the correlation process itself.
Solution Approach 2:
The invention replaces a complex mechanical phase-tracking system with a computational approach. Instead of using feedback loops or adaptive algorithms to continuously adjust phase alignment, the system substitutes a direct mathematical estimation of peak phase based on Doppler frequency calculations, simplifying the overall process while maintaining stability.
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 solution effectively compensates for Doppler-induced peak phase shifts, enabling accurate peak detection and enhancing receiving sensitivity in weak electric field environments by integrating correlation values with phase alignment.
Implementation Method 1
a Doppler shift occurs depending on a variation in relative positional relationship between a GPS satellite and a receiving device and the receiving frequency is shifted from 1.57542 [GHz] which is a carrier frequency of a GPS satellite signal
Data Source
AI summary
In a baseband processing circuit unit, a sample memory stores a received data sequence obtained by sampling a signal received by an RF receiving circuit unit at a given sampling time interval. A data sequence estimating unit estimates an estimated data sequence, which is obtained when the received signal is sampled at a sampling time shifted by a given shift time from the sampling time of the received data sequence, on the basis of the received data sequence stored in the sample memory. A correlation operation unit performs a correlation operation on the estimated data sequence estimated by the data sequence estimating unit 22 and a replica code. An integration unit integrates the correlation operation result from the correlation operation unit at a given integration time interval.