Signal Separation Apparatus Using Spatial Filtering and Decision Feedback
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Solution Overview
Problem
In optical communication systems, successive interference cancelers face challenges in accurately separating multiplexed signals due to the need for estimating the transmission path matrix H, which can lead to SNR degradation and residual inter-mode crosstalk, especially over long distances.
Innovation Solution
A signal receiving apparatus with a spatial filtering unit that separates equalized signals by multiplying received signals with predetermined weighting coefficients, including decision signals from other signal separating apparatuses, to improve signal separation accuracy without requiring precise estimation of the transmission path matrix H.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If successive interference cancelers estimate the transmission path matrix H, then signal separation can be performed, but SNR degradation and residual inter-mode crosstalk occur
Solution Approach 1:
The patent segments the signal separation process into multiple stages using multiple signal separating apparatuses. Each apparatus processes signals sequentially, with later apparatuses receiving both original received signals and decision signals from previous apparatuses. This segmentation allows progressive interference cancellation without requiring precise transmission path matrix estimation, thereby reducing SNR degradation while maintaining separation accuracy.
Solution Approach 2:
The patent applies preliminary action by having earlier signal separating apparatuses perform initial signal separation and generate decision signals before subsequent apparatuses process the same signals further. These preliminary decision signals are reused in later stages, enabling progressive refinement of signal separation without re-estimating the transmission path matrix, thus avoiding cumulative SNR degradation.
2Measurement precision
If successive interference cancelers estimate the transmission path matrix H, then signal separation can be performed, but residual inter-mode crosstalk remains
Solution Approach 1:
The patent divides the signal separation task across multiple apparatuses that sequentially process signals. Each apparatus reduces interference from specific modes, and the segmented approach allows progressive elimination of inter-mode crosstalk without leaving residual interference that would persist in a single-stage estimation approach.
Solution Approach 2:
The patent implements feedback by feeding decision signals from earlier signal separating apparatuses back into subsequent apparatuses. This feedback mechanism allows later apparatuses to use previously decoded information to further cancel interference, progressively reducing residual inter-mode crosstalk through iterative refinement.
3Measurement precision
If multiple signal separating apparatuses are used to improve separation accuracy, then signal separation performance improves, but device complexity increases
Solution Approach 1:
The patent applies universality by designing multiple signal separating apparatuses with identical functional structures. Each apparatus performs the same basic operation of separating signals using weighting coefficients, but they operate sequentially with different input combinations (original signals plus decision signals from previous apparatuses). This modular universality achieves high separation accuracy while keeping individual apparatus complexity manageable.
Data Source
AI summary
A signal receiving apparatus includes at least one signal separating apparatus that separates a specific signal from a plurality of received signals. Each of the at least one signal separating apparatus includes a spatial filtering unit that separates at least one equalized signal and a decision signal outputting unit that generates a first decision signal by deciding the equalized signal and outputs the generated first decision signal. The spatial filtering unit separates the at least one equalized signal by multiplying at least the plurality of received signals among the plurality of received signals and either the first decision signal output from the decision signal outputting unit or a second decision signal output from another signal separating apparatus by predetermined weighting coefficients.