FM Receiver Multi-Path Interference Removal via Joint Spatial-Temporal Filtering
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Solution Overview
Problem
Existing methods for mitigating multi-path interference in FM radio signals received by mobile receivers, particularly in vehicles, face challenges in converging to stable solutions due to the high number of unknowns and lack of correlation between spatial and temporal filtering processes, often prioritizing adjacent signals over desired ones, leading to stability issues.
Innovation Solution
A single iterative algorithm is implemented for both spatial and temporal filtering after linear combination of signals from multiple antennas, expressed in polar coordinates to introduce correlation between coefficients, facilitating faster and more stable convergence by minimizing a cost function related to the constant modulus of the combined signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If separate spatial and temporal filtering processes are used to mitigate multi-path interference, then the interference removal capability is improved, but the algorithm convergence stability deteriorates due to high number of unknowns and lack of correlation between processes
Solution Approach 1:
The patent combines separate spatial and temporal filtering processes into a unified joint filtering approach. The spatial filter processes signals from multiple antennas simultaneously with the temporal filter, creating a single integrated system that processes the combined signal. This merging reduces the total number of independent unknowns and establishes correlation between previously separate processes, thereby improving algorithm convergence stability while maintaining multi-path interference removal capability.
Solution Approach 2:
The patent changes the parameter representation by expressing filter coefficients in polar coordinates rather than Cartesian coordinates. This parameter transformation introduces correlation between the spatial and temporal filtering processes. By representing complex coefficients as magnitude and phase components, the joint filtering algorithm can more effectively constrain the solution space, leading to improved convergence stability without sacrificing interference mitigation performance.
2Object-affected harmful factors
If multiple unknowns are introduced in spatial and temporal filtering, then the interference removal capability is improved, but the convergence speed deteriorates
Solution Approach 1:
By merging spatial and temporal filtering into a single joint process, the patent reduces the total number of independent unknowns that must be solved simultaneously. The unified filter processes signals from multiple antennas with multiple time delays in one coordinated operation, rather than as separate sequential steps. This consolidation decreases computational complexity and accelerates convergence speed while maintaining the ability to remove multi-path interference.
Solution Approach 2:
The patent transforms the parameter space by using polar coordinate representation for filter coefficients. This change introduces natural constraints and correlations that reduce the effective dimensionality of the solution space. By expressing coefficients in terms of magnitude and phase rather than real and imaginary parts independently, the algorithm converges faster because the parameter transformation creates a more favorable optimization landscape with fewer independent variables to resolve.
3Measurement precision
If constant modulus algorithms are used to ensure constant signal modulus, then the signal processing accuracy is improved, but the device complexity increases due to iterative computational requirements
Solution Approach 1:
The patent merges spatial and temporal filtering operations into a single joint constant modulus algorithm. Instead of applying separate CMA algorithms to spatial and temporal filters independently, the unified filter applies a single CMA that simultaneously optimizes both spatial and temporal coefficients. This consolidation reduces the total number of iterative computations required while maintaining the constant modulus constraint, thereby reducing computational complexity without sacrificing signal processing accuracy.
Solution Approach 2:
The patent changes the parameter representation to polar coordinates, which simplifies the constant modulus constraint enforcement. By representing filter coefficients as magnitude and phase components, the CMA algorithm can more efficiently enforce the constant modulus condition. This parameter transformation reduces the computational burden of the iterative process while maintaining processing accuracy, as the polar representation naturally incorporates the modulus constraint into the optimization framework.
Data Source
AI summary
A method for decreasing multi-path interference, for a vehicle radio receiver including at least two radio reception antennas that each receive a plurality of radio signals composed of time-shifted radio signals resulting from a multi-path effect. The plurality of radio signals combined to deliver a combined radio signal ys to be played, with: yn=WnT[G1,nS, X1,n+G2,nS, X2,n] at time n, where x1 and x2 are vectors the components of which correspond to the plurality of signals received by the first antenna and by the second antenna, respectively, G1,nS and G2,nS are scalars the components of which are the complex weights of a spatial filter and wnT is the transpose matrix of a vector the components of which are the complex weights of a temporal filter. The method includes implementation of an iterative adaptation algorithm to determine the complex weights of the spatial filter and the complex weights of the temporal filter.