CSK Signal Reception Reducing Correlator Count
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Solution Overview
Problem
Current methods for receiving and processing Code Shift Keying (CSK) signals in GNSS receivers are inefficient due to the high number of correlators required, leading to increased hardware costs and noise immunity issues, especially when receiving two chip-by-chip multiplexed CSK signals.
Innovation Solution
A method that involves obtaining quadratures of a moved-to-zero-frequency signal, integrating and normalizing them, and using delay lines to calculate convolutions with a reference signal, allowing for the demodulation of CSK symbols with reduced hardware requirements and improved noise immunity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional correlation methods are used to receive chip-by-chip multiplexed CSK signals, then signal reception capability is achieved, but the number of correlators required increases dramatically (e.g., 1536 correlators for two multiplexed signals with M=8)
Solution Approach 1:
The patent divides the correlation function calculation into multiple segments by introducing intermediate correlation results. Instead of calculating all correlation points simultaneously, the method segments the calculation process into stages, where each stage computes a portion of the correlation function. This segmentation allows the system to process multiplexed CSK signals with far fewer correlators than the traditional approach requiring 1536 correlators.
Solution Approach 2:
The patent transforms the problem from a spatial dimension (multiple parallel correlators) to a temporal dimension (sequential calculation stages). By organizing the correlation calculation in time-based stages rather than requiring all correlators to operate simultaneously, the system achieves the same signal reception capability with dramatically reduced hardware complexity.
2Measurement precision
If a large number of correlators are deployed to receive multiplexed CSK signals, then complete correlation function coverage is achieved, but noise immunity deteriorates
Solution Approach 1:
The patent extracts and reuses intermediate correlation results across different correlation calculations. By identifying and utilizing common sub-calculations in the correlation function, the method avoids redundant computations and reduces the overall number of correlator operations needed, thereby improving noise immunity while maintaining complete correlation coverage.
Solution Approach 2:
The patent changes the computational parameters by introducing a staged calculation approach with intermediate results. This parameter transformation allows the system to achieve the same measurement precision with fewer operations, reducing the accumulation of noise errors that would otherwise occur in traditional exhaustive correlation methods.
3Measurement precision
If exhaustive correlation calculation is performed for all possible PRN offsets, then accurate signal detection is achieved, but processing time and computational load increase
Solution Approach 1:
The patent performs preliminary calculations of intermediate correlation results that can be reused in subsequent detection steps. By pre-computing these intermediate values, the system avoids redundant calculations during the actual signal detection process, significantly reducing processing time while maintaining accurate detection of all possible PRN offsets.
Solution Approach 2:
The patent maintains continuous useful action by chaining correlation calculations together through intermediate results. Each calculation stage builds upon previous results, creating a continuous computational flow that eliminates idle time and redundant operations, thereby reducing overall processing time while preserving detection accuracy.
Data Source
AI summary
A method of receiving two chip-by-chip multiplexed CSK signals (e.g., GNSS signals) and searching for a non-CSK signal with optimal performance at a given digit capacity of a sampling memory resided in parallel correlators. For CSK signals Prompt, Early and Late results for each of possible code shift are calculated as different sums of four punctured convolutions. Depending on configuration, the method allows to receive both multiplexed CSK signals with lesser quality or one of the CSK signals with better quality. The method can be implemented as an apparatus with four punctured correlators, a set of multipliers by 1 or 2N, another set of multipliers by 1 or 0, summers of four input to one result, a RAM, searchers of maximum, and conditional commutators.