Digital Microphone Array Beamforming via Shared Multiplexed Bus

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Solution Overview

Problem

Conventional microphones are cost-prohibitive for large arrays in consumer electronic devices due to increased fragility, manufacturing complexity, and limited noise rejection, which affects audio performance and dynamic range.

Innovation Solution

A digital microphone array is constructed using a noise bandwidth-limited supply voltage distributed through low-noise multiplexing, with a single high-capacitance capacitor near the head-end chip, and signals are multiplexed with data transfer through a shared bus, reducing the number of wires and costs, and enabling beamforming for improved audio reception.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional microphones are used to construct large arrays, then audio performance and dynamic range are improved, but manufacturing complexity and cost increase rapidly

Engineering Contradiction:

Improveaudio performanceVSAvoidmanufacturing complexity

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent divides the microphone system into multiple discrete digital microphone elements arranged in an array, where each element is a complete functional unit with its own ADC and processing capability. This segmentation allows standardization of individual units, simplifying manufacturing while enabling scalable array configurations for improved audio performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from analog to digital domain by incorporating ADCs within each microphone element, fundamentally changing the signal parameter domain. This digital transformation enables better noise immunity, easier signal processing, and simplified interconnection architecture, reducing manufacturing complexity while maintaining or improving audio performance.

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If microphone area is increased to improve dynamic range, then performance is improved, but cost and fragility increase

Engineering Contradiction:

Improvedynamic rangeVSAvoidcost

Core Design Contradiction:

Measurement precisionVSEase of manufacture

Solution Approach 1:

The patent combines multiple small-area digital microphone elements into an array configuration, where the collective effective area provides the required dynamic range and spatial coverage. This merging approach achieves the performance of a large microphone using multiple smaller, less fragile, and more cost-effective units.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent uses multiple identical or similar digital microphone element designs rather than one large custom design. Each element is a standardized copy that can be manufactured using the same process, reducing per-unit cost and complexity while the array of copies provides the cumulative performance needed.

Inventive Principle:

Principle #26Copying

3Measurement precision

If the number of microphones in an array is increased, then audio reception capability is improved, but the number of wire connections increases proportionally

Engineering Contradiction:

Improveaudio reception capabilityVSAvoidnumber of wire connections

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent implements a shared bus architecture where a single communication bus serves multiple functions: data transmission, control signaling, and power delivery to all microphone elements. This multi-functional bus replaces multiple separate wiring connections, reducing device complexity while maintaining full audio reception capability across the array.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent introduces a digital bus as an intermediary communication medium between the microphone elements and the processing unit. This digital intermediary consolidates multiple signal paths into a unified interface, dramatically reducing the number of physical connections required while preserving all necessary communication functions.

Inventive Principle:

Principle #24Intermediary (Mediator)

4Ease of manufacture

If digital microphones are used with limited noise rejection, then cost is reduced, but susceptibility to power supply noise increases

Engineering Contradiction:

ImprovecostVSAvoidnoise susceptibility

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The patent replaces analog noise filtering mechanisms with digital signal processing techniques. By performing noise rejection in the digital domain through algorithms rather than analog circuitry, the system maintains low cost while achieving superior noise immunity that is not limited by power supply noise or component tolerances.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Data Source

PatentUS9467778B2Beamforming a digital microphone array on a common platform

Publication Date: 2016.10.11 CIRRUS LOGIC INC

AI summary

An interface for an array of digital microphones in an electronic device may include a head-end chip coupled to the digital microphones through a bus. The bus may be shared by each microphone of the array of microphones and be multiplexed to allow transmission of data from the microphones to the head-end chip and transmission of power from the head-end chip to the array of digital microphones. The head-end chip may perform signal processing on receive data from the array of digital microphones to create beamforming arrays. The array of microphones may include microphones with different characteristics to improve performance of the array of microphones.