Microphone Assembly Digital Feedback Loop for Low-Frequency Overload

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Solution Overview

Problem

Portable communication devices face challenges in achieving high sound quality and robustness for microphone assemblies due to saturation and non-linearity of active amplification elements, leading to overload and distortion issues at high sound pressure levels.

Innovation Solution

A microphone assembly with a processing circuit that includes an analog-to-digital converter, a digital loop filter, and a digital-to-analog converter, which creates a feedback loop to filter and combine the microphone signal, effectively preventing low-frequency overload and distortion by using a digital feedback path to control the frequency response and suppress high-level low-frequency components.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Power

If traditional analog preamplification is used to amplify microphone signals, then signal strength is improved, but overload distortion and saturation occur at high sound pressure levels

Engineering Contradiction:

Improvesignal amplification capabilityVSAvoidoverload distortion and saturation

Core Design Contradiction:

PowerVSObject-affected harmful factors

Solution Approach 1:

The patent replaces the traditional analog preamplifier with a digital feedback loop system consisting of an ADC, digital loop filter, and DAC. This substitution eliminates the need for high-gain analog amplification that causes saturation and distortion at high sound pressure levels, while maintaining signal amplification capability through digital processing.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent implements a digital feedback loop where the ADC converts the microphone signal to digital, the digital loop filter processes it, and the DAC converts it back to analog for feedback to the preamplifier input. This feedback mechanism allows precise control of the frequency response and prevents overload distortion by digitally managing the amplification process.

Inventive Principle:

Principle #23Feedback

2Volume of moving object

If compact dimensions are used for portable devices, then device portability is improved, but microphone assembly size and power consumption are constrained

Engineering Contradiction:

Improvedevice compactnessVSAvoidmicrophone assembly integration

Core Design Contradiction:

Volume of moving objectVSDevice complexity

Solution Approach 1:

The patent integrates the ADC, digital loop filter, and DAC into a unified processing circuit that works together as a cohesive system. This merging of components allows the compact microphone assembly to achieve sophisticated signal processing capabilities without requiring separate discrete components, thus maintaining small form factor while reducing complexity.

Inventive Principle:

Principle #5Merging (Combining)

3Reliability

If digital feedback loop is implemented to control frequency response, then sound quality and robustness are improved, but circuit complexity increases

Engineering Contradiction:

Improvesound quality and robustnessVSAvoidprocessing circuit complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces complex analog frequency response control circuits with a digital feedback loop using ADC, digital loop filter, and DAC. This substitution achieves superior frequency response control and robustness through digital processing while simplifying the overall circuit design compared to traditional analog approaches.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

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

The solution enhances sound quality by accurately controlling the frequency response, reducing distortion, and improving the stability of the directional response in beamforming microphone arrays, while maintaining high signal resolution and reducing the vulnerability of preamplifiers to low-frequency induced overload.

Implementation Method 1

a transducer configured to convert sound into a microphone signal

Methodology Applied

Scientific EffectAcoustic transduction:

Implementation Method 2

a digital loop filter which includes an adjustable or fixed transfer function, the digital loop filter being configured to receive and filter the digital microphone signal

Methodology Applied

Scientific EffectDigital filtering: Filter (electronic)

Implementation Method 3

a digital-to-analog converter (DAC) configured to convert the first digital feedback signal into a corresponding analog feedback signal

Methodology Applied

Scientific EffectDigital-to-analog conversion:

Implementation Method 4

a summing node at the transducer output configured to combine the microphone signal and the analog feedback signal

Methodology Applied

Scientific EffectSignal summation:

Data Source

PatentUS10880646B2Microphone assembly with digital feedback loop

Publication Date: 2020.12.29 KNOWLES ELECTRONICS LLC

AI summary

A microphone assembly includes a transducer element and a processing circuit. The processing circuit includes an analog-to-digital converter (ADC) configured to receive, sample and quantize a microphone signal generated by the transducer element to generate a corresponding digital microphone signal. The processing circuit includes a feedback path including a digital loop filter configured to receive and filter the digital microphone signal to provide a first digital feedback signal and a digital-to-analog converter (DAC) configured to convert the first digital feedback signal into a corresponding analog feedback signal. The processing circuit additionally includes a summing node at the transducer output configured to combine the microphone signal and the analog feedback signal.