FM Spectral Phase Differencing for Wide-Lane Pseudorange Accuracy
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Solution Overview
Problem
Current signal processing techniques for wide-lane pseudorange measurements using FM signals face challenges in achieving accurate positioning due to rapid degradation of the recovered Signal-to-Noise Ratio (SNR) below a certain threshold, leading to significant pseudorange errors, especially in urban environments with multipath issues.
Innovation Solution
The proposed solution involves determining phases of multiple components of an FM signal and calculating phase differences to obtain pseudoranges, utilizing a receiver apparatus with tone generators, phase measurement circuits, and a processor to digitize and filter FM signals, enabling precise location determination despite SNR limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional signal processing techniques are used for wide-lane pseudorange measurements, then the system is simple to implement, but positioning accuracy degrades rapidly below a certain Carrier-to-Noise Ratio threshold due to significant pseudorange errors and multipath issues
Solution Approach 1:
The patent segments the FM signal into multiple spectral components (19 kHz pilot tone, 38 kHz stereo subcarrier, 57 kHz RDBS clock, etc.) and processes each component separately to extract phase information. This segmentation allows the system to achieve sub-meter positioning accuracy by combining phase measurements from multiple signal components, resolving the contradiction between measurement precision and device complexity through systematic signal decomposition
Solution Approach 2:
The patent transitions from conventional single-signal pseudorange measurement to multi-dimensional phase difference measurement by utilizing multiple spectral components of the FM signal simultaneously. By measuring phase differences across different frequency components (wide-lane, medium-lane, narrow-lane combinations), the system achieves robust positioning accuracy that is insensitive to signal-to-noise ratio degradation
2Measurement precision
If phase measurements are taken from multiple spectral components, then cycle ambiguities are resolved and sub-meter precision is achieved, but the number of processing steps and computational requirements increase
Solution Approach 1:
The patent performs preliminary squaring operations on the FM signal to generate doubled-frequency components before phase measurement. This preliminary action creates the necessary spectral components (e.g., squaring the 19 kHz pilot to generate 38 kHz, squaring the 38 kHz subcarrier to generate 76 kHz) that are then used for phase difference calculations, improving processing efficiency by preparing the signal structure in advance
Solution Approach 2:
The patent generates multiple copies of spectral components at different frequencies through squaring operations (e.g., creating 38 kHz from 19 kHz, 76 kHz from 38 kHz). These copied frequency components are then used to form wide-lane, medium-lane, and narrow-lane phase measurements, enabling the system to achieve sub-meter precision through redundant phase difference calculations without requiring additional external signal sources
Data Source
AI summary
Apparatus having corresponding methods and computer-readable media comprises a receiver to receive a wireless stereo frequency-modulation (FM) signal comprising a plurality of spectral signal components including a first tone and one or more frequency bands; one or more tone generators each to generate a respective second tone based on a respective one of the frequency bands; a plurality of phase circuits each to measure a phase of a respective one of the first and second tones; and a difference element to determine a phase difference between two of the phases.