In-band Resonance Piezo MEMS Microphone Equalization

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Conventional piezoelectric microphones often have resonance frequencies outside the desired operating frequency band, leading to suboptimal performance in audio applications, particularly in the audible frequency range of 20 Hz to 20,000 Hz.

Innovation Solution

Incorporating a piezoelectric sensor with an equalizer, either in digital or analog domain, and an application-specific integrated circuit (ASIC) that includes an analog-to-digital converter and calibration data to adjust or remove in-band resonance, ensuring the resonance frequency falls within the operating band and compensates for temperature and low-frequency corner variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional piezoelectric microphones are designed with resonance frequencies outside the audible range, then structural simplicity is maintained, but audio performance in the audible frequency range becomes suboptimal

Engineering Contradiction:

Improveaudio performanceVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent converts the harmful in-band resonance peak into a beneficial feature by deliberately designing the piezoelectric sensor to have its resonance frequency within the audible range, then using digital signal processing to remove the resulting peak. This approach allows the resonance to boost signal strength before removal, improving signal-to-noise ratio while maintaining audio fidelity.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces an equalizer as an intermediary component between the piezoelectric sensor and the output. This equalizer processes the signal to remove the resonance peak that was intentionally created, allowing the system to benefit from the resonance-enhanced signal while eliminating the unwanted frequency artifact.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If the resonance frequency is placed within the operating frequency band, then signal-to-noise ratio is improved, but the resonance peak must be removed to maintain flat frequency response

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidprocessing complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent replaces what would traditionally be a mechanical solution (designing the sensor to have resonance outside the audible range) with a digital signal processing solution. By using an equalizer to remove the resonance peak, the system achieves both signal-to-noise ratio improvement and flat frequency response through software rather than mechanical design constraints.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Volume of moving object

If piezoelectric sensors are made smaller to reduce device size, then integration is improved, but low-frequency response control becomes more difficult

Engineering Contradiction:

Improvesensor sizeVSAvoidlow-frequency response control

Core Design Contradiction:

Volume of moving objectVSManufacturing precision

Solution Approach 1:

The patent changes the approach to low-frequency response control from a physical parameter (sensor size and mechanical design) to a digital parameter (equalization filtering). By using digital signal processing to control the low-frequency corner, the system can achieve precise response control regardless of the small physical size of the piezoelectric sensor.

Inventive Principle:

Principle #35Parameter changes

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

This configuration enhances signal-to-noise ratio, reduces noise floor, allows for smaller sensor size, and provides precise control over low-frequency response, resulting in improved audio fidelity and cost-effectiveness.

Implementation Method 1

A piezoelectric sensor is designed to convert acoustic energy into an electrical signal

Methodology Applied

Scientific EffectPiezoelectric effect: Piezoelectric Effect

Implementation Method 2

The equalizer can be configured to provide the equalization in digital domain

Methodology Applied

Scientific EffectDigital equalization: Filter (electronic)

Data Source

PatentUS20230292045A1In-band resonance piezo MEMS microphones

Publication Date: 2023.09.14 SKYWORKS SOLUTIONS INC

AI summary

In some embodiments, a microphone can include a piezoelectric sensor configured to provide a response to acoustic energy in a frequency band, with the response including an in-band resonance having a peak frequency within the frequency band. The microphone can further include an equalizer coupled to the piezoelectric sensor and configured to provide equalization of the response of the piezoelectric sensor, such that the equalizer removes or adjusts the in-band resonance from the response of the piezoelectric sensor.