PMUT Array Beamforming for Ultrasonic Signal Quality
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Solution Overview
Problem
Conventional piezoelectric ultrasonic transducers face limitations in generating high-frequency acoustic waves with minimal diffraction and spurious reflections, leading to reduced signal quality and increased ring-up/ring-down times, which affect their performance in applications like fingerprint sensing and medical imaging.
Innovation Solution
A Piezoelectric Micromachined Ultrasonic Transducer (PMUT) device with a high-frequency operation, utilizing a substrate, edge support structure, and an interior support structure to minimize acoustic diffraction and spurious reflections, and employing phase delayed transmission in a two-dimensional array configuration for improved beamforming and signal processing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional piezoelectric ultrasonic transducers are used, then they can generate acoustic waves, but they suffer from acoustic diffraction and spurious reflections that reduce signal quality
Solution Approach 1:
The patent segments the ultrasonic transducer into multiple independent piezoelectric elements arranged in a two-dimensional array, allowing individual control of each element's phase and amplitude. This segmentation enables precise beamforming that minimizes acoustic diffraction and spurious reflections by controlling the interference patterns of sound waves from each element, thereby improving signal quality through constructive interference in desired directions and destructive interference in unwanted directions.
Solution Approach 2:
The patent transitions from conventional one-dimensional or single-element transducers to a two-dimensional array of piezoelectric elements. This dimensional expansion provides additional degrees of freedom for beamforming control, enabling more effective suppression of acoustic diffraction and spurious reflections by distributing and coordinating the acoustic output across multiple spatial dimensions, thus enhancing signal quality.
2Measurement precision
If conventional ultrasonic transducers operate at high frequency, then diffraction is reduced, but ring-up and ring-down times increase
Solution Approach 1:
By dividing the transducer into multiple independently controllable piezoelectric elements, the patent can apply different phase delays to each element. This enables the system to operate at high frequencies for reduced diffraction while using phased array beamforming to shorten the effective ring-up and ring-down times through constructive interference, resolving the time-quality tradeoff.
Solution Approach 2:
The patent employs periodic pulsed excitation of the piezoelectric elements with controlled phase relationships. By using short bursts of ultrasonic energy with precise phase timing across multiple elements, the system achieves high-frequency operation with minimized ring-up and ring-down times, as the periodic pulsing allows the acoustic field to build and decay more rapidly through constructive interference.
3Measurement precision
If a two-dimensional array of ultrasonic transducers is used with phase delayed transmission, then beamforming is improved, but device complexity increases
Solution Approach 1:
The patent divides the transducer into a two-dimensional array of segmented piezoelectric elements, each with independent phase and amplitude control. This segmentation enables sophisticated beamforming with phase delays to improve measurement precision, while the modular segmented structure makes the complexity manageable through standardized element designs and systematic control approaches.
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 PMUT device achieves reduced acoustic diffraction, shorter ring-up/ring-down times, and enhanced signal quality by operating at high frequencies and using phase delayed transmission in a two-dimensional array, improving the rejection of spurious reflections and increasing the fill-factor for better transmit and receive signals.
Implementation Method 1
Piezoelectric materials facilitate conversion between mechanical energy and electrical energy. Moreover, a piezoelectric material can generate an electrical signal when subjected to mechanical stress, and can vibrate when subjected to an electrical voltage. Piezoelectric materials are widely utilized in piezoelectric ultrasonic transducers to generate acoustic waves based on an actuation voltage applied to electrodes of the piezoelectric ultrasonic transducer.
Implementation Method 2
Piezoelectric materials facilitate conversion between mechanical energy and electrical energy. Moreover, a piezoelectric material can generate an electrical signal when subjected to mechanical stress
Data Source
AI summary
In a method for transmit beamforming of a two-dimensional array of ultrasonic transducers, a beamforming pattern to apply to a beamforming space of the two-dimensional array of ultrasonic transducers is defined. The beamforming space includes a plurality of elements, where each element of the beamforming space corresponds to an ultrasonic transducer of the two-dimensional array of ultrasonic transducers, where the beamforming pattern identifies which ultrasonic transducers within the beamforming space are activated during a transmit operation of the two-dimensional array of ultrasonic transducers, such that a generated ultrasonic beam is focused for reflecting from an object in contact with a contact surface of a platen overlying the two-dimensional array of ultrasonic transducers. The beamforming pattern is applied to the two-dimensional array of ultrasonic transducers. A transmit operation is performed by activating the ultrasonic transducers of the beamforming space according to the beamforming pattern.