GPS Signal Acquisition Using Nonlinear Processing and Circular Correlation
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Solution Overview
Problem
Current satellite navigation systems face high computational complexity during signal acquisition, especially with coherent integration, which increases power consumption and reduces sensitivity due to bit transitions in navigation data, necessitating a more efficient method for signal detection and synchronization.
Innovation Solution
A method involving nonlinear processing of satellite navigation signals, including complex conjugation, coherent averaging, and circular correlation to determine timing offsets, along with techniques for handling chip timing drift and interference cancellation, reduces computational burden and enhances sensitivity by mitigating the effects of bit transitions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If coherent integration period is increased to improve receiver sensitivity, then sensitivity is improved, but computational complexity increases proportionally to the square of the coherent integration time
Solution Approach 1:
The patent segments the coherent integration process into multiple non-overlapping integration periods, where each period processes a portion of the signal independently. This divides the computationally intensive operation into manageable chunks, reducing the peak computational burden while maintaining the total integration time needed for sensitivity improvement.
Solution Approach 2:
The patent performs preliminary processing of the received signal before coherent integration, including down-conversion to complex baseband and digitization. This preliminary action prepares the signal in a form that enables more efficient subsequent processing, reducing the computational complexity of the integration operation itself.
2Reliability
If hardware correlators are used in scan mode for signal acquisition, then signal detection capability is achieved, but search time is increased
Solution Approach 1:
The patent merges multiple correlator operations into a single integrated processing framework. Instead of sequentially scanning through each code phase and carrier frequency hypothesis with separate hardware correlators, the invention combines these operations into a unified algorithm that processes multiple hypotheses simultaneously, dramatically reducing search time while maintaining detection capability.
Solution Approach 2:
The patent replaces the mechanical hardware correlator scan approach with a software-based signal processing algorithm. By substituting physical hardware scanning with computational methods operating on digitized baseband signals, the system achieves faster acquisition without sacrificing detection reliability.
3Productivity
If frequency domain convolution is used to reduce search time, then acquisition speed is improved, but computational complexity becomes very high especially in unassisted receivers
Solution Approach 1:
The patent applies local quality by processing the signal in the complex baseband domain rather than performing full frequency domain convolution. This localized approach to signal representation and processing maintains the speed benefits of frequency domain methods while reducing the overall computational complexity, particularly for unassisted receivers without side information.
Data Source
AI summary
A method of acquiring signals from satellites in a Global Positioning System (GPS) is disclosed. The method includes receiving navigation signals from the satellites of the GPS, down-converting to complex baseband the received navigation signals to form a first signal, digitizing samples of the first signal, nonlinear processing of the digitized samples of the first signal to form a second signal, where the nonlinear processing comprises forming a weighted sum of products of pairs of the digitized samples at different relative delays, in which one of each of the pairs has been complex conjugated, coherent averaging the second signal over integer multiples or submultiples of a spreading sequence period of the navigation signals to form a third signal, performing circular correlation processing of the third signal with a representation of each navigation signal of the navigation signals and determining a timing offset at which a correlated output energy is maximized, based on the circular correlation processing.