Adaptive Filter Control for Narrowband Interference and Multipath
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Modern communication systems face challenges in effectively reducing narrowband interference due to intentional or unintentional jamming and multipath distortion, especially in wideband radio channels, which can cause bit errors and disrupt signal reception.
Innovation Solution
An adaptive filter circuit with variable delay and tap selection mechanisms, responsive to demodulator states and modulation types, is used to separate and mitigate multipath interference, incorporating algorithms like LMS, RLS, or MMSE for coefficient adjustment and interference reduction, while optimizing the number of adaptive taps and gain based on input and output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If adaptive filters with more filter taps are used to handle multiple interferers, then interference reduction capability is improved, but device complexity and platform resource usage increase
Solution Approach 1:
The patent implements dynamic adaptation of filter parameters including variable filter order selection, adaptive update gain adjustment based on demodulator state, and conditional activation of adaptive filtering. The filter transitions between different operational modes (training mode, tracking mode, disabled) based on signal conditions and demodulator performance, allowing the system to use complex filtering only when necessary while maintaining simplicity during stable operation
Solution Approach 2:
The system dynamically changes multiple parameters including filter order (number of taps), update gain values, and filter activation state based on input signal power, output signal power, and demodulator state. This allows the filter to adapt its complexity to match the actual interference conditions, using more taps and higher update gains when multiple interferers are present while reducing complexity when the signal environment is stable
2Object-affected harmful factors
If adaptive filter updates are performed continuously to track changing interference, then interference reduction effectiveness is improved, but processing time and computational load increase
Solution Approach 1:
The patent implements periodic update cycles for adaptive filter coefficients based on demodulator state transitions between training and tracking modes. During training mode, updates occur more frequently to establish initial filter coefficients, while during tracking mode, updates occur less frequently to maintain coefficients. This periodic updating strategy balances tracking effectiveness with processing time by adapting the update rate to the current operational phase
Solution Approach 2:
The system dynamically adjusts the update gain parameter based on demodulator state, using higher update gains during training mode for faster adaptation and lower update gains during tracking mode for smoother coefficient adjustments. This dynamic gain control allows the filter to quickly acquire interference characteristics initially while maintaining stability during ongoing operation, reducing unnecessary processing during stable tracking periods
3Object-affected harmful factors
If adaptive filtering is applied to all signal portions including preamble and data, then overall interference reduction is improved, but signal distortion and demodulation errors may increase
Solution Approach 1:
The patent segments the signal processing into distinct phases: preamble processing and data processing, with different adaptive filter configurations for each. During preamble processing, the filter operates in training mode with specific update gains to learn interference characteristics without affecting synchronization accuracy. During data processing, the filter transitions to tracking mode with adjusted parameters to maintain interference reduction while preserving signal integrity for accurate demodulation
Solution Approach 2:
The system uses feedback from demodulator state (training mode vs. tracking mode) and signal power measurements to control adaptive filter operation. The demodulator state provides feedback about signal quality and synchronization status, which is used to adjust filter update gain and determine whether adaptive filtering should be active. This feedback loop ensures the filter enhances rather than degrades signal quality by adapting its behavior to current demodulation conditions
Data Source
AI summary
A communications system receives a modulated signal that carries encoded communications data. An adaptive filter circuit has a plurality of adaptive filters each having a plurality of non-adaptive and adaptive filter taps with weighted coefficients. At a selected adaptive filter, an interference reduction circuit is responsive to one of at least a received state of a demodulator, the type of modulation used by communication system and the input and output power of adaptive filter for updating the adaptive gain of the adaptive filter, selecting the number and order of adaptive filter taps, separating the spacing of multipath introduced by adaptive filter, controlling input and output normalizing circuits to adaptive filter(s) and selecting if signal passed to demodulator is original received signal or signal output by adaptive filter. A demodulator and decoder receive the filtered output signal and demodulate and decode the signal to obtain the communications data.