Split Electrode PMUT for Extended Ultrasonic Sensing Range
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Solution Overview
Problem
Conventional air-coupled Piezoelectric Micromachined Ultrasonic Transducers (PMUTs) are limited by their maximum operating range due to the strength of transmitted signals and the ability to resolve received signals, leading to restricted sensing applications.
Innovation Solution
The implementation of a split electrode design, which includes both a center electrode and a ring/outer electrode split into multiple sections, enhancing the signal-to-noise ratio by providing stronger transmission and more sensitive reception.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional single electrode design is used in air-coupled PMUTs, then the device structure is simple, but the maximum operating range is limited due to weak transmitted signals and poor signal resolution
Solution Approach 1:
The electrode is divided into multiple segments (e.g., four segments) arranged in a specific pattern around the membrane aperture. This segmentation allows independent control of each segment, enabling differential drive modes that enhance transmitted signal strength and improve received signal resolution, thereby extending the maximum operating range without requiring a complete redesign of the PMUT structure
2Length of moving object
If the transmitted signal strength is increased to extend operating range, then the sensing range improves, but the signal-to-noise ratio may deteriorate due to increased noise interference
Solution Approach 1:
The segmented electrode design enables selective activation of specific segments during transmission and reception phases. By controlling which segments are active, the system can enhance transmitted signal strength while simultaneously optimizing received signal quality, maintaining a high signal-to-noise ratio across extended sensing ranges
Solution Approach 2:
The system employs periodic switching between different drive modes (e.g., omnidirectional, directional, transmit, receive) by sequentially activating different electrode segment combinations. This periodic action allows the transducer to optimize performance for each function while maintaining overall signal quality and noise rejection
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 design enables longer sensing ranges and improved signal-to-noise ratios, allowing for more effective transmission and reception of ultrasonic signals, thereby expanding the applications of PMUTs.
Implementation Method 1
a piezoelectric layer disposed above the bottom electrode layer
Implementation Method 2
a piezoelectric layer disposed above the bottom electrode layer
Data Source
AI summary
An ultrasonic transducer device comprises a piezoelectric micromachined ultrasonic transducer (PMUT), a transmitter with first and second differential outputs, and a controller. The PMUT includes a membrane layer. A bottom electrode layer, comprising a first bottom electrode and a second bottom electrode, is disposed above the membrane layer. The piezoelectric layer is disposed above the bottom electrode layer. The top electrode layer is disposed above the piezoelectric layer and comprises a segmented center electrode disposed above a center of the membrane layer and a segmented outer electrode spaced apart from the segmented center electrode. The controller, responsive to the PMUT being placed in a transmit mode, is configured to couple the first and second segments of the bottom electrode layer with ground, couple the first output of the transmitter with the segments of the segmented center electrode, and couple the second output with the segments of the segmented outer electrode.