Dual-Electrode pMUT Membrane Layout for Ultra-Wide Bandwidth
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Solution Overview
Problem
Conventional piezoelectric transducer arrays have limited bandwidth, which affects the axial resolution in applications requiring a wide range of frequencies, such as fetal heart monitoring and arterial monitoring.
Innovation Solution
A piezoelectric micromachined ultrasonic transducer (pMUT) array with dual electrodes, including a first and second drive/sense electrodes, is used to excite and sense both a first and second mode of vibration in the membrane, allowing for improved signal processing capabilities and a wide bandwidth by controlling the relative strength and phase of the electrical signals.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single drive/sense electrode is used in conventional pMUT arrays, then the device structure is simple, but the bandwidth is limited
Solution Approach 1:
The single electrode is segmented into two separate drive/sense electrodes with different geometries. The first electrode has a smaller area and the second electrode has a larger area, allowing each to excite different vibrational modes (first and second modes) in the membrane, thereby expanding the operational bandwidth of the transducer
Solution Approach 2:
The patent transitions from a single-electrode configuration to a multi-electrode configuration, adding dimensional complexity to the electrode structure. This enables independent control of different vibrational modes through separate drive signals, achieving greater than 100% fractional bandwidth
2Measurement precision
If the bandwidth is increased to improve axial resolution, then the imaging capability is enhanced, but the damping requirements become more complex
Solution Approach 1:
The patent employs dynamic control of the two drive/sense electrodes by applying drive signals with different phases. By adjusting the phase relationship between the signals applied to the first and second electrodes, the transducer can dynamically switch between exciting the first vibrational mode, the second vibrational mode, or both simultaneously, achieving wide bandwidth without complex passive damping 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 dual electrode design achieves a greater than 100% fractional bandwidth, enabling high-frequency operation up to 60 MHz, improving image quality and sensitivity in applications like high-frequency intravenous ultrasound devices.
Implementation Method 1
An ultrasonic piezoelectric transducer device typically includes a piezoelectric membrane capable of vibrating in response to a time-varying driving voltage to generate a high frequency pressure wave
Implementation Method 2
The same piezoelectric membrane can also receive reflected pressure waves from the propagation media, and convert the received pressure waves into electrical signals
Data Source
Figure 1A~1B
Figure 1C
Figure 2A~2B
AI summary
An apparatus comprising: a piezoelectric micromachined ultrasonic transducer (100), pMUT, including a piezoelectric membrane (114) disposed on a substrate (101), a reference electrode coupled to the membrane; a first and second drive/sense electrodes (102, 103) coupled to the membrane to drive or sense a first and second modes of vibration in the membrane; wherein the piezoelectric membrane has a circular or spheroidal or ellipsoidal geometry and is anchored to the substrate (101) at a perimeter of the membrane, wherein the first drive/sense electrode (102) has a circular or spheroidal geometry with a diameter smaller than that of the membrane and with a center aligned to a center of the membrane, the second drive/sense electrode (103) has an annular geometry with a center aligned to the center of the membrane, with an outer diameter smaller than that of the membrane and with an inner diameter greater than an outer diameter of the first drive/sense electrode.