Spatio-Temporal Multi-Correlator for Multipath Discrimination
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Solution Overview
Problem
Satellite navigation systems, such as GPS and GLONASS, face significant location errors in urban environments due to multipath signals, which are difficult to distinguish from the useful signal, especially when they have low delays relative to the useful signal, and existing solutions require substantial computational resources or are inefficient with small antenna arrays.
Innovation Solution
A satellite location device with at least two radiolocation signal sensors and signal processing means implementing a maximum likelihood estimation algorithm, using a spatio-temporal multi-correlator architecture with delay lines and correlators to estimate parameters like propagation delay, Doppler frequency, and direction of arrival, allowing for effective discrimination of useful signals from multipath signals with reduced computational resources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional multi-antenna algorithms are used for spatial filtering, then spatial sampling of wavefront is achieved, but spatial resolution and correlation between sources are poor due to small array size
Solution Approach 1:
The patent transitions from purely spatial filtering to spatio-temporal filtering by adding the time dimension through multiple correlators with different integration times. This allows the system to achieve better source separation and spatial resolution without increasing the physical antenna array size, effectively resolving the contradiction between measurement precision and device complexity.
2Measurement precision
If SAGE algorithm is used for spatio-temporal-frequency approach, then all signal parameters including multipath can be estimated, but substantial computational resources are required preventing real-time processing
Solution Approach 1:
The patent segments the signal processing into multiple parallel correlators, each with different integration times, that operate simultaneously. This segmentation allows the system to estimate multiple signal parameters including multipath components while maintaining real-time processing capability through parallel computation, resolving the contradiction between measurement precision and productivity.
3Measurement precision
If time domain discrimination is used to separate useful signal from multipath, then signal discrimination is attempted, but it fails when multipath signals have low delay relative to useful signal
Solution Approach 1:
The patent moves from one-dimensional time domain discrimination to multi-dimensional spatio-temporal discrimination by incorporating both spatial information from multiple antennas and temporal information from correlators with different integration times. This additional dimensionality enables the system to distinguish low delay multipath signals from useful signals that would be indistinguishable in pure time domain, resolving the detection difficulty.
4Measurement precision
If decomposition into singular values is used with few antennas, then subspace identification is achieved, but the method is only valid when number of antennas exceeds number of paths received
Solution Approach 1:
The patent compensates for the limited number of antennas by adding the time dimension through multiple correlators with different integration times. This creates a spatio-temporal data structure that provides sufficient degrees of freedom for subspace identification even when the spatial dimension (number of antennas) is small, thereby expanding the method's adaptability to consumer-grade devices with limited antennas.
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 reduces memory and computational load, enabling real-time processing and improved location accuracy in urban environments, independent of the satellite navigation system, and is robust to RF stage limitations, achieving performance comparable to conventional SAGE algorithms with significantly reduced resource requirements.
Implementation Method 1
a step of correlation with a local code of the signal received by said sensors by means of correlators
Implementation Method 2
The processing lines comprise at least one delay line connected by a first end to the output of the correlator and by a second end to an input of the signal processing means, the delay introduced corresponding to a multiple of the integration time of the correlators
Implementation Method 3
The radio frequency signal emitted by a satellite is coded and the time taken by this signal to reach the receiver to be located is used to determine the distance
Implementation Method 4
signal processing means able to implement a maximum likelihood estimation algorithm, each of said sensors being connected to at least two signal processing lines
Data Source
AI summary
The invention relates to a location device capable of discriminating a useful signal from multi-path signals. The device comprises at least two radiolocation-signal sensors (A1, A2) and signal-processing means (μΡ) capable of implementing an algorithm for estimating a maximum likelihood, each of said sensors (A1, A2) being connected to at least two signal-processing lines, each processing line including a correlator (C11, C12) and being arranged such that the signal-processing means (μΡ) can calculate parameters representative of the useful signal and of the multi-path signals from the signals from the processing lines. The processing lines include at least one delay line (R11m) connected, at a first end thereof, to the output of the correlator (C11), and, at the second end thereof, to an input of the signal-processing means (μΡ), the inserted delay corresponding to a multiple of the integration time of the correlators. The invention can be used in reference ground stations or ground stations for observing navigation-satellite constellations, and can be used in mobile terminals for improving the navigation solution in urban or even airport environments.