Segmented MEMS Sound Transducer for Audio and Ultrasonic Sensing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing ultrasonic transceivers are large, narrowband, and have limited sensitivity due to poor impedance matching and single-ended readout, limiting their effectiveness in both sending and receiving modes.
Innovation Solution
A MEMS sound transducer element with a first electrode structure partitioned into electrically isolated segments, allowing dual functionality as both an audio and ultrasonic emitter/receiver, utilizing a flexible membrane and counter electrode configuration to enhance sensitivity and frequency range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If bulky piezoelectric actors are used for ultrasonic speakers and receivers, then they can provide sufficient power and sensitivity, but they become large in size (cm2 range) and narrowband due to resonant mode operation
Solution Approach 1:
The backplate is divided into multiple electrically isolated electrode segments that can be independently controlled. This segmentation allows different portions of the backplate to function as emitters or receivers simultaneously, enabling full-duplex operation and improving power efficiency while reducing the required device area.
Solution Approach 2:
The same membrane and backplate structure serves multiple functions: it acts as both an ultrasonic emitter and receiver, and also functions as an audio transducer. This multi-functionality eliminates the need for separate dedicated ultrasonic and audio transducers, significantly reducing device area while maintaining sufficient power and sensitivity.
2Reliability
If piezoelectric transducers operate in resonant mode to achieve sufficient sensitivity, then they provide good reception capability, but they become very narrowband
Solution Approach 1:
The system dynamically switches between different operational modes (emitter/receiver) and frequency ranges (ultrasonic/audio) by controlling different electrode segments. This dynamic operation allows the transducer to achieve high sensitivity at ultrasonic frequencies when needed while also responding to audio frequencies, effectively expanding the usable frequency range without sacrificing sensitivity.
Solution Approach 2:
The electrical parameters (voltage, frequency, phase) applied to different electrode segments are independently controlled and changed. By adjusting these parameters, the same physical structure can operate at different frequencies and modes, achieving both high sensitivity at resonant frequencies and broad frequency coverage through parameter modulation.
3Device complexity
If a single-ended readout is used in dual backplate MEMS microphone technology, then the structure is simplified, but the reachable SNR is strongly limited
Solution Approach 1:
The backplate is segmented into multiple electrically isolated electrodes that can be independently read out. This segmentation enables differential readout schemes where signals from different segments are compared, canceling common-mode noise and significantly improving SNR while maintaining relatively simple circuitry.
Solution Approach 2:
The system uses feedback mechanisms where the output from receiver segments is fed back to control the emitter segments or to adjust the readout amplification. This feedback improves the effective SNR by actively compensating for noise and optimizing the signal path.
4Device complexity
If the sound generating membrane is pulled to one side only, then the structure is simplified, but half the stroke height is lost
Solution Approach 1:
Instead of pulling the membrane in one direction from a neutral position, the system uses push-pull actuation where the membrane can be displaced in both directions from its equilibrium position by controlling the voltage polarity on the backplate electrodes. This inversion of the actuation approach doubles the effective stroke height while maintaining structural simplicity.
Solution Approach 2:
The membrane displacement is dynamically controlled by switching the voltage polarity and magnitude applied to different backplate segments. This dynamic control enables bidirectional movement with optimized stroke height for different operational modes (emission vs. reception) without requiring complex mechanical structures.
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 MEMS sound transducer achieves high sensitivity and wideband operation across human-audible and ultrasonic ranges, addressing the limitations of existing technologies with improved impedance matching and dual-mode functionality.
Implementation Method 1
a first electrode structure, wherein a conductive material of the first electrode structure comprises a plurality of electrically isolated electrode segments. The MEMS sound transducer element further comprises a second electrode structure spaced apart from the first electrode structure, wherein the first electrode structure and the second electrode structure are operable as an audio sound transducer.
Implementation Method 2
a first subset of the plurality of electrically isolated electrode segments of the first electrode structure is, in conjunction with the second electrode structure, operable as an ultrasonic or audio emitter. A second subset of the plurality of the electrically isolated electrode segments of the first electrode structure is, in conjunction with the second electrode structure, operable as an ultrasonic or audio receiver.
Data Source
AI summary
A MEMS sound transducer element is operable in an audio and an ultrasonic range. The MEMS sound transducer element includes a first electrode structure, wherein a conductive material of the first electrode structure includes a plurality of electrically isolated electrode segments, and a second electrode structure spaced apart from the first electrode structure, wherein the first electrode structure and the second electrode structure are operable as an audio sound transducer. A first subset of the plurality of electrically isolated electrode segments of the first electrode structure is, in conjunction with the second electrode structure, operable as an ultrasonic or audio emitter, and a second subset of the plurality of the electrically isolated electrode segments of the first electrode structure is, in conjunction with the second electrode structure, operable as an ultrasonic or audio receiver.