Adaptive Signal Combining Device with Dual-Step Filter Control
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Solution Overview
Problem
In optical space communication systems, accurately estimating signal-to-noise ratio (SNR) for reception signals with extremely small SNR values is challenging due to high noise components, and existing methods struggle with high-speed SNR estimation and filter coefficient calculation, especially under rapid atmospheric fluctuations.
Innovation Solution
A signal combining device and method that utilize adaptive filters with different step sizes for first and second filter coefficients, allowing for high-speed and accurate calculation of filter coefficients, and switching the update state of filter coefficients based on the magnitudes of second filter coefficients to maintain a predetermined state of combined signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If adaptive control is performed for filter coefficients to track rapid SNR fluctuations, then responsiveness to atmospheric changes improves, but calculation accuracy deteriorates due to noise in low SNR conditions
Solution Approach 1:
The patent implements dynamic adaptation by switching between two operational modes: a tracking mode with large step sizes that responds quickly to SNR changes, and a refinement mode with small step sizes that achieves high precision when SNR is stable. This dynamic switching resolves the contradiction between speed and accuracy by adapting the control parameters to current signal conditions
Solution Approach 2:
The patent changes the step size parameter of the adaptive filter based on SNR estimation. When SNR is high, a large step size is used for rapid tracking; when SNR is low, a small step size is used to prevent noise-induced errors. This parameter adaptation allows the system to optimize both responsiveness and accuracy under different operating conditions
2Adaptability or versatility
If filter coefficients are continuously updated to track atmospheric fluctuations, then adaptation to channel changes improves, but convergence time increases and bit error rates worsen due to noise
Solution Approach 1:
The system dynamically adjusts the update behavior of filter coefficients based on current SNR conditions. During low SNR periods, updates are suppressed or performed with minimal step sizes to avoid introducing noise-related errors, thereby maintaining reliability. During high SNR periods, aggressive updates are enabled to quickly adapt to atmospheric changes
Solution Approach 2:
The patent employs feedback mechanisms where SNR estimation results are fed back to control the adaptive filter's step size and update frequency. This feedback loop ensures that coefficient updates are performed only when signal conditions are favorable, preventing noise from degrading bit error rate while maintaining adaptability to genuine channel variations
3Measurement precision
If multiple filters are used for signal processing, then signal combination quality improves, but device complexity and computational load increase
Solution Approach 1:
The patent segments the signal processing function into multiple independent filter branches, each processing a different reception signal. These segmented filters can be independently optimized and controlled, allowing high-quality signal combination while maintaining manageable complexity through modular architecture
Solution Approach 2:
The patent employs universal filter structures that perform multiple functions: they act as adaptive equalizers during low SNR conditions and as combiners during high SNR conditions. This multi-functionality reduces overall system complexity by eliminating the need for separate specialized components for each function
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
Enables high-speed and accurate combination of reception signals by preventing filter coefficient updates during low SNR conditions and quickly adapting to SNR fluctuations, improving bit error rates and reducing convergence time for filter coefficients.
Implementation Method 1
The coherent receivers 93 generate reception signals by mixing the optical signals and output light of a local oscillator (LO) 94 and then performing photoelectric conversion
Data Source
AI summary
The signal combining device includes: a plurality of first filters to subject each of a plurality of reception signals to processing with first filter coefficients, the plurality of reception signals being generated by subjecting optical signals to coherent detection; a plurality of second filters to subject outputs of the first filters to processing with second filter coefficients; a combiner to output combined signals acquired by combining outputs of the second filters; and a controller to perform adaptive control for each of the first filter coefficients and each of the second filter coefficients with different step sizes in each other, so that the combined signals are in a predetermined state, based on the reception signals input to the first filters and the combined signals, and to switch an update state of a filter coefficient of each of the first filters, based on magnitudes of the second filter coefficients.