Adaptive Microphone Array Null Steering via Lookup Table

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Solution Overview

Problem

Adaptive microphone arrays often fail to effectively cancel side interference, especially when sources of noise are in motion or multiple sources are present, leading to suboptimal noise reduction in speech recognition systems.

Innovation Solution

The implementation of a mirrored adaptive microphone array that uses test signals to steer the null direction for interference cancellation, allowing for real-time adaptation and minimization of amplitude response in specific angular orientations, thereby enhancing noise reduction capabilities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional adaptive algorithms are used to minimize error signal at the output of adaptive filter, then the array cancels the most significant source of interference that carries the most energy, but this approach may not provide sufficient cancellation of noise sources in cases where enhancement for robust speech recognition is needed

Engineering Contradiction:

Improvenoise cancellation effectivenessVSAvoidability to cancel specific directional interference

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The system performs preliminary action by pre-calculating and storing optimal weight sets for multiple predetermined angular bearings in a lookup table before real-time operation. During runtime, the system quickly retrieves the appropriate pre-computed weights based on the detected null direction, avoiding the need to perform complex adaptive filtering calculations in real-time. This resolves the contradiction by enabling effective cancellation of specific directional interference through pre-prepared solutions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements dynamics by making the null direction steerable and adaptable to different angular orientations. The lookup table contains weight sets for multiple predetermined angular bearings, allowing the system to dynamically select and switch between different cancellation patterns based on the actual direction of interference. This provides both the reliability of targeted cancellation and the adaptability to handle different noise sources from various directions.

Inventive Principle:

Principle #15Dynamics

2Reliability

If the adaptive microphone array tracks and cancels coherent sources of interference, then cancellation is provided for the most energetic source, but the array geometry and multiple interference sources may result in insufficient cancellation of other noise sources

Engineering Contradiction:

Improveinterference cancellation performanceVSAvoidarray configuration and weight adjustment complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The system performs preliminary action by pre-calculating optimal weight sets for multiple predetermined angular bearings and storing them in a lookup table before real-time operation. During runtime, the system quickly retrieves the appropriate pre-computed weights based on the detected null direction, avoiding the need to perform complex adaptive filtering calculations in real-time. This resolves the contradiction by enabling effective cancellation of specific directional interference through pre-prepared solutions.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system uses a lookup table that contains copies of optimal weight sets for different angular bearings. Instead of recalculating weights from scratch for each interference scenario, the system retrieves pre-computed weight copies that are optimized for specific directions. This reduces computational complexity while maintaining cancellation effectiveness across multiple interference sources.

Inventive Principle:

Principle #26Copying

3Reliability

If beam forming techniques are used to increase gain in desired directions, then signal-to-noise ratio is improved, but the array response in other directions is not sufficiently minimized

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoiddirectional response control precision

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system changes parameters by adjusting the null direction parameter to different angular orientations based on the detected interference source. The lookup table contains weight sets optimized for different angular bearings, allowing the system to change the directional response characteristics dynamically. This provides precise control over the array response in specific directions while maintaining the beam forming gain in desired directions.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9479885B1Methods and apparatuses for performing null steering of adaptive microphone array

Publication Date: 2016.10.25 MOTOROLA MOBILITY LLC

AI summary

Configuring an adaptive microphone array to gather signals from a main lobe of the array, and configuring the array to reduce side interference gathered from sources that are not situated within the main lobe. A memory stores test signals gathered by the array at a plurality of predetermined angular bearings with reference to the array in an anechoic chamber. Signals gathered in real time are processed to provide a preliminary output and preliminary weights. The test signals are retrieved from memory. The preliminary weights are applied to the test signals to provide null steering weights. The null steering weights and the preliminary output are processed to reduce or minimize the amplitude response of the array at the angular orientation.