MEMS Microphone Integrated Resistor Heater for Acoustic Self-Test
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Microphone assemblies face challenges in controlling internal acoustic noise, which affects the signal-to-noise ratio and complicates self-test applications and noise cancellation due to the proximity of the signal to the microphone, leading to undesirable ambient noise.
Innovation Solution
Integration of an air-insulated resistor within the MEMS transducer, electrically isolated from the transducer, allows for controlled heat generation to produce acoustic signals, enabling purposeful noise cancellation and self-test functionalities by programming the integrated circuit to drive current through the resistor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a resistor is integrated within the MEMS transducer for controlled heat generation, then acoustic signal generation capability is improved, but electrical isolation complexity increases
Solution Approach 1:
The MEMS transducer is segmented into distinct functional regions: the diaphragm assembly for acoustic sensing, the resistor structure for heat generation, and the insulating material layer for electrical isolation. This segmentation allows each component to perform its specific function while maintaining electrical isolation between the resistor and transducer electrical contacts.
Solution Approach 2:
An insulating material layer is introduced as an intermediary between the resistor and the transducer electrical contacts. This intermediate layer provides the necessary electrical isolation while allowing the resistor to be integrated within the transducer structure, enabling controlled acoustic signal generation without electrical interference.
2Power
If the resistor is placed close to the MEMS transducer for effective heat generation, then acoustic signal strength is improved, but ambient noise interference increases
Solution Approach 1:
The resistor is designed to convert electrical energy into thermal energy, which then generates controlled acoustic signals. By positioning the resistor within the transducer housing but electrically isolated from the diaphragm, the heat-generated acoustic signals can be used for self-test and noise cancellation functions, turning potential noise into a useful signal source.
Solution Approach 2:
The resistor is positioned in a specific location within the transducer housing where it can effectively generate heat and acoustic signals without directly contacting the diaphragm. This localized positioning allows the resistor to provide acoustic signal generation capability while maintaining spatial separation to minimize ambient noise interference with the primary sensing function.
3Area of stationary object
If the resistor is integrated on the same substrate as the MEMS transducer, then device compactness is improved, but thermal interference with the transducer increases
Solution Approach 1:
An insulating material layer is positioned between the resistor and the MEMS transducer substrate. This intermediate insulating layer provides thermal isolation while allowing both components to be integrated on the same substrate, achieving device compactness without significant thermal interference between the heat-generating resistor and the sensitive transducer.
Solution Approach 2:
A thin insulating film or layer is used to separate the resistor from the transducer substrate. This thin insulating barrier provides sufficient thermal isolation to prevent heat transfer to the transducer while maintaining the compact integrated structure, as the thin film minimizes space requirements.
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 effectively reduces ambient noise interference, enhances the functionality of MEMS microphones, and allows for controlled acoustic signal generation, improving the signal-to-noise ratio and enabling self-test capabilities.
Implementation Method 1
The integrated circuit can be programmed to drive current through the resistor to heat the enclosed back volume to a predetermined temperature to thereby produce a known acoustic signal
Implementation Method 2
The transducer is a variable capacitor comprising a fixed electrode and a movable electrode
Data Source
AI summary
A microelectromechanical system (MEMS) transducer for integration in a microphone assembly is designed to produce heat-generated acoustic signals. The MEMS transducer generally comprises a substrate having an aperture, a transduction element located at least partially over the aperture and coupled to the substrate, electrical contacts coupled to the transduction element, and a resistor integrated with the substrate or the transduction element. The resistor is coupled to electrical contacts that are electrically isolated from the contacts of the MEMS transducer or transduction element. The transduction element includes an insulating material coupled to the substrate. The transduction element comprises a fixed electrode and a movable electrode located at least partially over the aperture of the substrate. The fixed electrode or the moving electrode is formed on the insulating material. The resistor can be formed on the insulating material or suspended from the insulating material.