CN117665828A

CN117665828A - Transducer and imaging system

Info

Publication number: CN117665828A
Application number: CN202211029594.XA
Authority: CN
Inventors: 陈旭颖; 于媛媛; 徐景辉; 谢金; 屈梦娇
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-08-25
Filing date: 2022-08-25
Publication date: 2024-03-08
Also published as: WO2024041179A1

Abstract

The utility model provides a transducer and imaging system, array that forms through the coupling of the transduction unit of equidimension can realize the transmission and the receipt of fundamental frequency section and harmonic wave band in same transduction unit to increase fundamental frequency transmission and receiving bandwidth, and realize harmonic imaging simultaneously. The transducer array includes: a plurality of transduction units arranged in an array on a substrate; the vibrating diaphragm of each transduction unit comprises a structural layer, an upper electrode, a piezoelectric layer and a lower electrode; the plurality of transduction units are divided into at least one reference subunit and at least one compensation subunit, the length-to-width ratio of the reference subunit is not smaller than that of the compensation subunit, the reference subunit is used for generating resonance in a fundamental frequency band and a harmonic band, the compensation subunit generates resonance in the fundamental frequency band or the harmonic band at the same time, and the resonance frequency of the compensation subunit in the fundamental frequency is different from that of the reference subunit in the fundamental frequency, so that the transceiving bandwidth of the fundamental frequency is widened.

Description

Transducer and imaging system

Technical Field

The present application relates to the field of ultrasound imaging, and more particularly to a transducer and an imaging system.

Background

Transducers are used in a variety of situations where energy conversion is required, such as ultrasonic transducers, where conversion of mechanical signals, i.e., acoustic signals and electrical signals, is achieved. Taking a micromechanical piezoelectric ultrasonic transducer (Piezoelectric micromachined ultrasonic transducer, PMUT) as an example, PMUT realizes mutual conversion of an acoustic wave signal and an electric signal based on a positive and negative voltage effect. When transmitting sound waves, the piezoelectric material drives the vibrating diaphragm to vibrate under the inverse piezoelectric effect by applying alternating signals between the upper electrode and the lower electrode so as to generate the sound waves; when receiving sound waves, the vibrating diaphragm vibrates under the driving of the external sound waves, the piezoelectric material generates charges through the piezoelectric effect and reads electric signals through the upper electrode and the lower electrode, and the electric signals can be used for imaging, such as imaging targets reflecting the sound waves.

In general, the imaging resolution of a PMUT is related to the bandwidth of the PMUT, the greater the bandwidth, the higher the axial resolution. Therefore, how to improve the imaging resolution of the transducer is a problem to be solved.

Disclosure of Invention

The utility model provides a transducer and imaging system, array that forms through the coupling of the transduction unit of equidimension can realize the transmission and the receipt of fundamental frequency section and harmonic wave band in same transduction unit to increase the transmission and the receipt bandwidth of fundamental frequency, and can realize harmonic imaging's demand.

In a first aspect, the present application provides a transducer comprising: a plurality of transduction units and a substrate, the plurality of transduction units being arranged in an array on the substrate;

specifically, each of the transduction units includes an upper electrode and a lower electrode, when an acoustic wave is emitted, an excitation electric signal is applied to the upper electrode and the lower electrode to vibrate the diaphragm to generate the acoustic wave, and when the acoustic wave is received, the transduction unit is deformed to generate electric charges between the upper electrode and the lower electrode, and a reception electric signal is output through the upper electrode and the lower electrode, the reception electric signal being used to generate an output image;

the plurality of transduction units can be divided into at least one reference subunit and at least one compensation subunit, the length-to-width ratio of the reference subunit is not smaller than the length-to-width ratio of the compensation subunit, the length-to-width ratio of the reference subunit is not smaller than a first threshold value, so that the reference subunit is used for generating resonance in a fundamental frequency band and a harmonic band, the compensation subunit generates resonance in the fundamental frequency band, the first threshold value is calculated according to the fundamental frequency band and the harmonic band, and the size of the transduction unit is calculated according to the resonance frequency of the transduction unit; in addition, the sizes of the compensation subunit and the reference subunit are not identical with the side length or the length-width ratio of the reference subunit, so that the resonance peak of the compensation subunit at the base frequency band is different from the resonance peak of the reference subunit at the base frequency band, the resonance peak of the compensation subunit and the reference subunit in the base frequency band are coupled, and the resonance bandwidth of the transducer at the base frequency band is increased. And the harmonic band is the frequency multiplication of N of the fundamental frequency, N is a positive integer greater than 1, the harmonic band can be the frequency multiplication of the fundamental frequency, the frequency multiplication of three times, etc., namely the harmonic band can include the frequency point that the resonance peak of third order resonance, fifth order resonance, etc. corresponds.

The aspect ratio of the reference subunit and the compensation subunit is the aspect ratio of the cross-section of the reference subunit and the compensation subunit in the direction perpendicular to the substrate, or the aspect ratio of the cross-section in the direction toward the substrate, and the cross-section is understood to be at least two symmetry axes perpendicular to each other, i.e. the ratio between the two symmetry axes perpendicular to each other.

Therefore, in the embodiment of the application, the surface of the substrate is provided with the transduction units with different sizes arranged according to the array, the transduction units with different sizes can receive the received waves with different frequency bands, and the staggered coupling of the resonance peaks of different subunits in the fundamental frequency band achieves the complementary effect of the wave peaks and the wave troughs, so that the effect of large bandwidth of the fundamental frequency is obtained through the coupling of multiple resonance peaks; and the high-order mode of each transduction unit is designed to be near the frequency doubling of the fundamental frequency center frequency, so that the function of harmonic wave receiving is realized, the harmonic wave imaging is further realized, and the imaging resolution is improved.

In one possible embodiment, the first threshold may be calculated according to the condition that the reference subunit needs to resonate in the fundamental frequency band and the harmonic bandI.e. the aspect ratio of the reference subunit is usually not less than +. >The harmonic receiving function can be ensured, the third-order mode of the reference subunit is at least positioned at the frequency doubling position of the first-order mode, and the receiving of the base band and the harmonic band is realized.

In one possible embodiment, the compensation subunit also resonates in the harmonic section. The size of the compensation subunit can be adjusted, so that the compensation subunit can realize harmonic wave segment receiving and harmonic wave imaging while the fundamental frequency resonates to widen the bandwidth of the base band.

In one possible embodiment, at least one reference subunit and at least one compensation subunit are arranged in a central symmetry on the substrate, so as to realize a symmetrical vibration mode, and the receiving of the fundamental frequency band and each harmonic band can be realized, so that the increase of the receiving bandwidth is realized.

In one possible embodiment, the upper electrode includes a plurality of segmented electrodes, and the received electrical signal is acquired through a center electrode of the plurality of segmented electrodes when the charge is generated between the upper electrode and the lower electrode, and the center electrode may include at least one electrode nearest to a geometric center point of the upper electrode. Therefore, the upper electrode of the transduction unit can be divided into a plurality of segmented electrodes, when signals are transmitted, different transmission modes and receiving frequency bands can be realized by exciting different segmented electrodes, and when the signals are transmitted and received, large-bandwidth transmission and reception can be realized.

In one possible embodiment, when emitting sound waves, each of the plurality of segmented electrodes is excited; when receiving signals, the central electrode is used for acquiring the received electric signals, namely, the area with the largest stress amplitude and consistent sign of each order of modes is used as the receiving electrode, so that the receiving of multiple modes can be considered, and meanwhile, the receiving sensitivity of the central electrode is higher than that of the electrode design corresponding to the stress distribution of each order of modes only because the electrode position is the largest stress part of each mode.

In one possible embodiment, the plurality of segmented electrodes may be divided into at least one inner electrode and at least one outer electrode, the at least one outer electrode surrounding the at least one inner electrode; when transmitting sound waves, adopting inverse excitation to at least one external electrode and at least one internal electrode; when receiving sound waves, differential receiving can be adopted for at least one external electrode and at least one internal electrode, so that inverse excitation and differential receiving are realized through the internal electrode and the external electrode, the receiving capacitance can be further increased, and the parasitic interference resistance is improved.

In one possible embodiment, the plurality of segmented electrodes are arranged symmetrically. Therefore, the reception sensitivity of modes such as one, three, and five steps can be considered by using the center electrode for reception when the center electrode is used for receiving signals by the symmetrically arranged segmented electrodes.

In one possible implementation, the plurality of segmented electrodes of each transduction unit are asymmetrically arranged, so that an asymmetric electrode design is adopted to excite an asymmetric vibration mode of the vibrating diaphragm, generation of even-order modes (namely wave troughs) is restrained, sensitivity difference between odd-order modes (such as 1, 3 orders and the like) is reduced, and accordingly bandwidth is increased.

In one possible embodiment, the distance between adjacent transducer elements is no more than 1.5 times the fundamental wavelength, thereby ensuring that grating lobes do not appear in the transducer array radiated sound field.

In one possible embodiment, the transduction unit comprises micromechanical piezoelectric ultrasonic transducer PMUT cells, and a piezoelectric sensing layer is further disposed between the upper electrode and the lower electrode in each PMUT cell.

In a possible embodiment, the transduction unit comprises a micromechanical capacitive ultrasound transducer CMUT unit, the upper electrode and the lower electrode comprising an insulating layer between them, a cavity being provided in the insulating layer.

In one possible embodiment, the shape of the plurality of transducing element surfaces may comprise at least one of an ellipse or a polygon (e.g. rectangle or square, etc.) having at least two central symmetry axes, and the aspect ratio of the reference subunit is greater than 1.

In one possible embodiment, the shape of the at least one reference subunit surface is at least one of a rectangular ellipse or a polygon with at least two central symmetry axes, and the shape of the at least one compensation subunit surface is a circle or a regular polygon.

In one possible implementation, the width of the array is less than 1.5 times the operating wavelength of the transducer.

In a second aspect, the present application provides a transducer comprising: a substrate and a plurality of transduction units arranged on the substrate; each of the transduction units includes an upper electrode and a lower electrode, when emitting sound waves, an excitation electric signal is applied to the upper electrode and the lower electrode to vibrate the diaphragm to generate sound waves, when receiving the sound waves, the transduction unit generates deformation when transmitting the sound waves to the transduction unit to generate charges between the upper electrode and the lower electrode, and the upper electrode and the lower electrode output receiving electric signals, which are used for generating output images; wherein the aspect ratio of each of the transduction units is greater than 1, and the upper electrode of each of the transduction units includes a plurality of segmented electrodes asymmetrically arranged along a central axis parallel to the short sides of the substrate.

In the embodiment of the application, the asymmetric electrode design is adopted to excite the asymmetric vibration mode of the vibrating diaphragm, so that the generation of the asymmetric mode of even order is excited, and the sensitivity difference between the modes of odd order (such as 1, 3 order and the like) is reduced, thereby increasing the transceiving bandwidth.

In one possible implementation manner, the number of the segmented electrodes in the upper electrode is related to the required highest order mode, for example, the number of the electrodes can be (n+1)/2 blocks, and the required highest order level is the n-order mode, so that the number of the segmented electrodes can be adjusted according to the actual application scene, thereby meeting the requirement of the actual scene and having strong generalization.

In one possible embodiment, the first threshold value may be calculated according to the condition that the transducer unit needs to resonate in the fundamental frequency band and the harmonic bandI.e. the aspect ratio of the reference subunit is usually not less than +.>The harmonic receiving function can be ensured, the third-order mode of the reference subunit is at least positioned at the frequency doubling position of the first-order mode, and the receiving of the base band and the harmonic band is realized.

In one possible implementation, the first threshold may be calculated according to the frequency of the basebandI.e. the aspect ratio of the reference subunit is usually not less than +.>The harmonic receiving function can be ensured, the third-order mode of the reference subunit is at least positioned at the frequency doubling position of the first-order mode, and the receiving of the base band and the harmonic band is realized.

In one possible embodiment, when emitting sound waves, each of the plurality of segmented electrodes is excited; when receiving sound waves, the receiving electric signals are acquired through the central electrode, wherein the central electrode is at least one electrode closest to the central point of the upper electrode, namely, the area with the largest stress amplitude of each mode and consistent sign is used as the receiving electrode, so that the receiving of multiple modes can be considered, and meanwhile, the receiving sensitivity of the central electrode is higher than that of the electrode design corresponding to the stress distribution of each mode only because the electrode position is the largest stress part of each mode.

In one possible embodiment, the shape of the plurality of transducing element surfaces may include at least one of an ellipse or a polygon (e.g., rectangle or square, etc.) having at least two central symmetry axes, increasing the manufacturability of the transducers provided herein.

In one possible implementation, the transduction unit includes micromechanical piezoelectric ultrasonic transducer PMUT units, and a piezoelectric sensing layer is further disposed between the upper electrode and the lower electrode in each PMUT unit, and is configured to collect a charge signal generated based on a mechanical signal.

In a third aspect, the present application provides an imaging system comprising: a probe and a processor;

providing a transducer as mentioned in any of the alternative embodiments of the first or second aspects in the probe;

the probe is used for transmitting ultrasonic waves to the target area and receiving ultrasonic echoes returned by the target area so as to obtain ultrasonic echo data;

the processor is configured to generate an ultrasound image from the ultrasound echo data.

Optionally, the imaging system may further include: and a display for displaying the ultrasound image.

In one possible embodiment, a plurality of transducers are provided in the probe, the plurality of transducers being arranged in an array. The plurality of transducers form a plurality of channels, such as one channel per column in an array, for acquiring echo signals to enable high resolution ultrasound imaging as well as harmonic imaging.

Drawings

FIG. 1 is a schematic diagram of an imaging system provided herein;

FIG. 2 is a schematic view of a probe structure provided in the present application;

fig. 3 is a schematic structural diagram of a PMUT provided in the present application;

FIG. 4 is a schematic diagram of a transducer according to the present application;

fig. 5 is a schematic structural diagram of another PMUT cell provided herein;

fig. 6 is a schematic structural diagram of a CMUT cell provided in the present application;

FIG. 7 is a schematic diagram of another transducer provided herein;

FIG. 8 is a schematic diagram of another transducer provided herein;

FIG. 9 is a schematic diagram of a receiving effect of a transducer according to the present application;

FIG. 10 is a schematic diagram of the receiving effect of another transducer provided herein;

FIG. 11 is a schematic diagram of another transducer provided herein;

FIG. 12 is a schematic diagram of the receiving effect of another transducer provided herein;

FIG. 13 is a schematic diagram of the receiving effect of another transducer provided herein;

FIG. 14 is a schematic view of another transducer provided herein;

FIG. 15 is a schematic view of the receiving effect of another transducer provided herein;

FIG. 16 is a schematic view of the receiving effect of another transducer provided herein;

FIG. 17 is a schematic diagram of another transducer provided herein;

fig. 18 is a schematic structural diagram of another transducer provided herein.

Detailed Description

The following description of the technical solutions in the embodiments of the present application will be made with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are only some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

The terms "first," "second," "third," "fourth" and the like in the description and in the claims of this application and in the above-described figures, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments described herein may be implemented in other sequences than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

The transducer provided by the application can be applied to various scenes of mechanical signal and electric signal conversion, such as wearing equipment, ultrasonic imaging scenes, ultrasonic ranging or communication scenes and the like. Specifically, the present invention relates to a method for manufacturing a semiconductor device. For example, the method can be used for tissue imaging of users and also can be applied to detection and flaw detection of industrial devices aiming at the requirements of large bandwidth and harmonic imaging in the ultrasonic imaging field. For another example, the transducers provided herein may be provided in a flexible substrate for real-time imaging of a user's tissue.

Illustratively, the imaging system provided herein may be as shown in fig. 1. The imaging system may include a probe that may transmit ultrasound waves to a target tissue and receive echo signals returned from the target tissue, a processor that may process the echo signals to generate an ultrasound image, and a display device.

It will be understood that the imaging probe emits sound waves to the human body, the imaging tissue reflects the sound waves and is received by the imaging probe, the imaging probe processes the signals through internal circuits and algorithms, and then the processed signals are transmitted to the display device in a cable or wireless (not shown in fig. 1) manner, and the APP for data processing is built in the display device, so that the received signals can be converted into picture signals and displayed in real time.

Specifically, the transducer provided by the application can be arranged in the probe, when the acoustic wave signal is sent, the transducer provided by the application converts the electrical signal into the acoustic wave signal and radiates outwards, and when the acoustic wave signal is received, the transducer provided by the application converts the acoustic wave signal into the electrical signal.

The display device is an optional device and can be used for displaying the ultrasonic image, so that a user can observe the specific condition of the target tissue conveniently. Of course, in some scenarios, it may not be necessary to display the ultrasound image in a display device.

Illustratively, a probe structure is taken as an example, as shown in FIG. 2. The probe may include a control circuit, an Analog Front End (AFE) circuit, a transducer, or the like. A selector switch may be provided between the transducer and the AFE circuitry for switching between transmitting and receiving signals.

Optionally, a protective layer or an acoustic lens structure may be disposed at the front end of the probe, where the protective layer is typically a polymer material and may function to protect the circuit structure inside the probe from physical impact and chemical corrosion. The acoustic lens may be used to converge acoustic waves.

The transducer is arranged at the front end of the probe, and when the protective layer is arranged at the same time, the transducer is tightly attached to the protective layer, the transducer is used for transmitting and receiving ultrasound, and the transducer can be provided by the following embodiments of the application.

An AFE circuit is arranged at the rear end of the transducer, and a transmitting excitation channel and an echo receiving channel are selected through a switch, wherein the transmitting excitation channel comprises a pulse transmitter for generating a pulse excitation waveform with a certain frequency and replication. The echo receiving circuit may include one or more of a time gain compensation circuit (time gain compensation, TGC), a low noise amplification circuit (low noise amplifier, LNA), a filtering circuit, an analog-to-digital conversion circuit (analog to digital converter, ADC), etc., for compensating, amplifying, filtering, and analog-to-digital converting the received echo signal.

The back end of the AFE circuit may be provided with a control chip, as shown in fig. 2, which is exemplified by a programmable logic gate (field programmable gate array, FPGA), and may be used for signal control and processing.

Specifically, the transducer may convert electrical energy into acoustic signals for transmission into a target object, for example, a PMUT device that converts electrical energy into acoustic energy for transmission to an imaging object via an inverse piezoelectric effect and converts echo acoustic energy of the imaging object into electrical signals via a positive piezoelectric effect. The PMUT unit structure main body comprises a basal layer (containing a cavity, wherein the plane size of the cavity determines the area of the vibrating diaphragm), a bottom electrode, a piezoelectric layer and an upper electrode. Obviously, the transducer is critical for the reception of acoustic signals.

Taking PMUT as an example, the PMUT structure can be as shown in fig. 3.

The PMUT can be used for ultrasonic imaging as an ultrasonic transceiver, and the principle of ultrasonic imaging is that acoustic reflection is generated at each tissue interface by utilizing acoustic impedance difference of different imaging tissues, and imaging can be realized by receiving reflected sound waves and performing signal processing. To achieve high resolution ultrasound imaging, the bandwidth of the PMUT needs to be optimized from the device side: longitudinal resolution R of ultrasound imaging _ax C/2 Δf, C is the speed of sound in the medium, typically affected by the material, Δf is the bandwidth, and obviously the bandwidth size directly affects the size of the resolution. In addition, the harmonic imaging function can also greatly improve the contrast and the transverse resolution of ultrasonic imaging. The working principle is as follows: by receiving the harmonic frequency band generated by the nonlinear effect of the transmitted sound wave in the medium propagation process, the sound wave with frequency doubling is usually mainly imaged, so that the harmonic imaging requires the transducer to have a receiving function at the frequency doubling of the fundamental frequency.

Some commonly used PMUTs typically achieve inadequate bandwidth, resulting in poor ultrasound imaging.

For example, some conventional PMUT devices, including a plurality of PMUT cells, the shape of the upper electrode may be rectangular or elliptical in shape, and the rectangular (or elliptical) PMUT cells may excite a plurality of modes within the fundamental frequency bandwidth. By adjusting the resonance characteristics of different rectangular PMUT units, complementary compensation of peaks and troughs is achieved, so that large bandwidth is achieved, and the rectangular PMUT units are additionally introduced for harmonic wave segment reception. However, the additional introduction of PMUT cells for harmonic reception only reduces the sensitivity of the array, and the fundamental frequency transmitting and harmonic receiving cells do not overlap in spatial location, affecting harmonic imaging performance.

For another example, for a segmented electrode design of a rectangular PMUT, the electrode segmented design excites different PMUT modes by adopting different excitation electrode configurations according to the stress distribution of first, third and fifth order modes, thereby realizing a multi-frequency PMUT. However, only one mode can be excited under one electrode configuration, that is, excitation of different modes cannot be simultaneously realized, so that the scheme can only realize multifrequency PMUT, but each mode cannot be coupled within a bandwidth, and cannot realize a large bandwidth. And the electrode blocks are more, and the lead wires and the excitation mode are complex.

For example, the multimode coupling PMUT unit structure adopts an asymmetric electrode design to excite an asymmetric vibration mode of the PMUT vibrating diaphragm, inhibit the generation of even-order modes (wave troughs), reduce the sensitivity difference between odd-order modes (such as 1 and 3 orders), and realize mode coupling within the bandwidth range of-3 dB. However, the PMUT cell bandwidth gain is limited. Only the modal coupling of the emission performance is considered, the increase of the emission bandwidth is realized, the receiving performance is not considered, the receiving bandwidth is reduced, the PMUT comprehensive bandwidth is not increased, and therefore, the imaging effect is not enhanced.

Therefore, the transducer is provided, and the array formed by coupling the transduction units with different sizes can realize the receiving and transmitting of the fundamental frequency band with large bandwidth and the receiving of the harmonic wave band in the same transduction unit, so that the bandwidth of the fundamental frequency receiving and transmitting is increased, the imaging resolution is improved, and the requirement of harmonic imaging can be met.

The structure of the transducer provided in the present application is described below.

Referring to fig. 4, a schematic structural diagram of a transducer is provided.

The transducer may include a plurality of transducing units 401 arranged in an array on a substrate 402.

Specifically, each of the transduction units includes a diaphragm, which may include a structural layer, an upper electrode, and a lower electrode, and upon transmitting an acoustic wave, an excitation electric signal is applied to the upper and lower electrodes to vibrate the diaphragm to generate the acoustic wave, and upon receiving the acoustic wave, the diaphragm is deformed to generate electric charges between the upper and lower electrodes and output a reception electric signal through the upper and lower electrodes, the reception electric signal being used to generate an output image.

The plurality of transducer units can be divided into at least one reference subunit and at least one compensation subunit based on the size, namely, the at least one reference subunit and the at least one compensation subunit are arranged on a substrate according to an array, the length-to-width ratio of the reference subunit is not smaller than the length-to-width ratio of the compensation subunit, and the length-to-width ratio of the reference subunit is not smaller than a first threshold value, so that the reference subunit can be used for generating resonance in both a fundamental frequency band and a harmonic band, the compensation subunit can generate resonance in the fundamental frequency band, the first threshold value can be calculated according to the fundamental frequency band and the harmonic frequency band of the reference subunit, which are required to be subjected to resonance, even though the fundamental frequency band and the harmonic frequency band of the reference subunit are simultaneously generated, the size of each transducer unit can be calculated according to the frequency characteristics of resonance required, and generally different sizes, such as different length-to-width ratios or different side lengths, can realize transmission and reception of sound wave signals of different frequency bands, so that the coupling of the reference subunit and the compensation subunit in the fundamental frequency band can be widened through coupling of the transducer units of different sizes to the base frequency band and the harmonic frequency band.

Therefore, in the embodiment of the application, the surface of the substrate is provided with the transduction units with different sizes arranged according to the array, the transduction units with different sizes can receive the received waves with different frequency bands, and the staggered coupling of the resonance peaks of different subunits in the fundamental frequency band achieves the complementary effect of the wave peaks and the wave troughs, so that the effect of large bandwidth of the fundamental frequency is obtained through the coupling of multiple resonance peaks; and the high-order mode of each transduction unit can be designed to be near the frequency doubling of the fundamental frequency center frequency, so that the function of harmonic wave receiving is realized, the harmonic wave imaging is further realized, and the imaging resolution is improved.

It should be noted that, in the fundamental frequency band mentioned in the present application, for the frequency required for ultrasonic imaging, each transducer unit generally resonates one frequency point in the fundamental frequency band, and the compensation subunit and the reference subunit generally resonates different frequency points in the fundamental frequency band, so that each resonance peak of different subunits is coupled in a staggered manner in the fundamental frequency band to achieve the complementary effect of the peak and the trough, and the transceiving bandwidth of the fundamental frequency is increased.

And typically the frequency of the output received electrical signal is related to the resonant frequency of the transducing unit. Such as the frequency at which the electrical signal is received, includes the resonant frequency of the transducing unit or a frequency adjacent to the resonant frequency.

In addition, in order to make the reference subunit and the compensation subunit resonate at different frequency points of the base band, different sizes, such as different length-width ratios and/or different side lengths, can be set for the reference subunit and the compensation subunit, so that the resonance peaks of the reference subunit and the compensation subunit are different frequency points, and the staggered coupling of the resonance peaks of different subunits is realized to achieve the complementary effect of the wave crest and the wave trough. The detailed calculation process of the dimension of the transducer unit can refer to the calculation process in scenario one mentioned below, and will not be described herein.

In one possible embodiment, the first threshold value may be calculated according to the frequency of the fundamental frequency band to be resonated and the harmonic frequency of the reference subunitI.e. the aspect ratio of the reference subunit is usually not less than +.>The harmonic receiving function can be ensured, the third-order mode of the reference subunit is at least positioned at the frequency doubling position of the first-order mode, and the receiving of the base band and the harmonic band is realized. In general, in order to ensure the receiving of the harmonic by the transduction unit, at least the third order mode of the reference subunit is required to be located at the frequency doubling of the first order mode, and the normal +.>

In one possible embodiment, the compensation subunit may also resonate in the harmonic section. The size of the compensation subunit can be adjusted, so that the compensation subunit can realize harmonic wave segment receiving and harmonic wave imaging while the fundamental frequency resonates to widen the bandwidth of the base band.

Of course, in some scenarios, the compensation subunit may only resonate the harmonic segment, so as to enhance harmonic imaging, and may specifically be adjusted according to the actual application scenario.

Optionally, the at least one reference subunit and the at least one compensation subunit may be arranged in a central symmetry manner on the substrate, so as to implement a symmetrical radiation sound field, radiate acoustic signals outwards perpendicular or close to perpendicular to the substrate, and implement transmission and reception of the fundamental frequency band and each harmonic band.

Alternatively, the upper electrode includes a plurality of segmented electrodes through the center electrode of which the reception electric signal is acquired when electric charges are generated between the upper electrode and the lower electrode, and the center electrode may be understood as one or more electrodes closest to a center point in the upper electrode. Therefore, the upper electrode of the transduction unit can be divided into a plurality of segmented electrodes, when signals are transmitted, different transmission modes and receiving frequency bands can be realized by exciting different segmented electrodes, and when the signals are transmitted and received, the large-bandwidth transmission and receiving can be realized, so that the large-bandwidth imaging can be realized.

Specifically, when the acoustic wave is transmitted, the plurality of partial quick electrodes can be excited, when the acoustic wave is received, the acoustic wave can be received through the central electrode, namely, the area with the largest stress amplitude of each order mode and consistent sign is used as the receiving electrode, so that the receiving of multiple modes can be considered, and meanwhile, the receiving sensitivity of the central electrode is higher than the receiving sensitivity designed according to the stress distribution of each order mode only because the electrode position is the largest stress part of each mode.

Alternatively, the plurality of electrodes may be divided into at least one inner electrode and at least one outer electrode, the at least one outer electrode surrounds the inner electrode, reverse excitation may be applied to the inner electrode and the outer electrode when transmitting sound waves, differential reception may be performed through the center electrode when receiving sound waves, that is, the phases of the reception signals of the inner electrode and the outer electrode are opposite, and the center electrode may include the inner electrode and the outer electrode disposed on the central axis, so that differential reception may be achieved through the inner electrode and the outer electrode, and reception capacitance may be further increased, and parasitic interference resistance may be improved.

In one possible scenario, the individual segmented electrodes in the transduction unit are arranged symmetrically and are generally symmetrical along a central axis parallel to the broadside. Therefore, the reception sensitivity of modes such as one, three, and five steps can be considered by using the center electrode for reception when the center electrode is used for receiving signals by the symmetrically arranged segmented electrodes.

In another possible scenario, the plurality of segmented electrodes in the transduction unit may also be arranged asymmetrically, so that an asymmetric electrode design is used to excite an asymmetric vibration mode of the diaphragm, excite the generation of an even-order asymmetric mode, reduce the sensitivity difference between odd-order modes (such as 1, 3, etc.), and increase the bandwidth.

Alternatively, the present application also provides a transducer, which is different from the transducer shown in fig. 4 in that the upper electrode of the transducer may include a plurality of segmented electrodes arranged asymmetrically on the substrate along a central axis parallel to the short sides of the substrate.

It is to be understood that the present application also provides a transducer comprising: a substrate and a plurality of transduction units arranged on the substrate; each of the transducer units includes an upper electrode and a lower electrode, when transmitting sound waves, an excitation electric signal is applied to the upper electrode and the lower electrode to vibrate the diaphragm to generate sound waves, when receiving the sound waves, the transducer units deform to generate charges between the upper electrode and the lower electrode, and the upper electrode and the lower electrode output a receiving electric signal, the frequency of the receiving electric signal is related to the frequency of resonance generated by each transducer unit, and the receiving electric signal is used for generating an output image; wherein the aspect ratio of each of the transduction units is greater than 1, and the upper electrode of each of the transduction units includes a plurality of segmented electrodes asymmetrically arranged along a central axis parallel to the short sides of the substrate.

In the case of an asymmetric arrangement of segmented electrodes, the dimensional structure of the individual transducer elements can be referred to in the foregoing description of the reference subunits, and will not be described here for the same.

For example, for a high-frequency scene, in general, no harmonic wave is required to be received at this time, a plurality of block electrodes in the transduction unit may be arranged in an asymmetric manner, for example, the sizes of the block electrodes are different, so that the reception of a base band is mainly achieved, or the reception of a low-order mode may also be considered, so that the reception of waves of each band is achieved through the block electrodes with different sizes, and the bandwidth can be widened.

Typically, the distance between adjacent transducer elements is no more than 1.5 times the fundamental wavelength, thereby ensuring that the radiated sound field of the array does not exhibit grating lobes.

In one possible scenario, the foregoing transduction unit may comprise a PMUT unit. The diaphragm in each PMUT cell may include an upper electrode, a lower electrode, and a piezoelectric sensing layer disposed between the upper electrode and the lower electrode, the upper electrode and the piezoelectric sensing layer being operable to collect a charge signal generated based on the acoustic wave signal.

For example, the structure of the PMUT cell may be as shown in fig. 5, and the membrane of the PMUT cell may include an upper electrode 501, a piezoelectric sensing layer 502, a lower electrode 503, and a structural layer 504, and the PMUT cell may further include a substrate 505, in which a cavity is disposed in the substrate 505, and the piezoelectric sensing layer 502 is disposed between the upper electrode 501 and the lower electrode 503.

When the PMUT unit is in a transmitting mode, alternating signals can be applied between the upper electrode and the lower electrode, the piezoelectric induction layer drives the vibrating diaphragm to vibrate wholly under the inverse piezoelectric effect so as to generate sound waves, the sound waves are transmitted outwards, and when the sound waves reach target tissues, the target tissues reflect the ultrasonic waves, so that the ultrasonic waves are reflected back to the PMUT unit.

When the PMUT unit is in a receiving mode, and echoes reflected by target tissues are transmitted to the vibrating diaphragm, the vibrating diaphragm vibrates under the driving of the echoes, the piezoelectric sensing layer generates charges less than the generated charges through piezoelectricity and transmits the charges to the upper electrode and the lower electrode, and the received electric signals can be read through the upper electrode and the lower electrode.

Therefore, the transduction unit provided by the application can adopt a PMUT structure, so that the conversion of mechanical signals and electric signals is realized, and the transmission and the reception of the mechanical signals are realized.

In another possible scenario, the aforementioned transduction unit may comprise a micromechanical capacitive ultrasound transducer (Capacitive micromachined ultrasonic transducer, CMUT) unit. An insulating layer is arranged between the upper electrode and the lower electrode, and a cavity is arranged in the insulating layer.

For example, the structure of the CMUT cell may be as shown in fig. 6, the CMUT cell may comprise a diaphragm, which may comprise an upper electrode 601, an insulating layer 602, a lower electrode 603, and a structural layer 604, the CMUT cell may further comprise a substrate 605, a cavity is provided in the insulating layer 602, and the insulating layer 602 is provided between the upper electrode 601 and the lower electrode 603.

When the CMUT cell is in the transmitting mode, a voltage can be applied between the upper electrode and the lower electrode, and the vibrating diaphragm is bent and deformed under the action of electrostatic force, so that the vibrating diaphragm is excited to reciprocate by applying alternating voltage with a required frequency to the upper electrode and the lower electrode, the electric energy is converted into mechanical energy, and the energy is radiated outwards, so that ultrasonic waves are generated.

When the CMUT unit is in a receiving mode, direct-current bias voltage is loaded between the upper electrode and the lower electrode, the vibrating diaphragm achieves static balance under the action of electrostatic force and vibrating diaphragm restoring force, when echoes reflected by target tissues are transmitted to the vibrating diaphragm, the vibrating diaphragm is excited to vibrate, the space between the upper electrode and the lower electrode is changed, and capacitance between the upper electrode and the lower electrode is changed, so that receiving electric signals are output.

Therefore, in the embodiment of the application, the transduction unit provided by the application can adopt a CMUT structure, so that the conversion of a mechanical signal and an electric signal is realized, and the transmission and the reception of an acoustic wave signal are realized.

Alternatively, the shape of the surface of the transduction unit, i.e., the shape formed by the surface structural layer or the base layer, may include at least one of a rectangle, an ellipse, or a polygon in particular. It is understood that the shape of the surface of the transducing element may comprise at least one of an ellipse or a polygon with at least two perpendicular symmetry axes.

In one possible implementation manner, the shape of the surface of the reference subunit is at least one of ellipse or polygon with at least two central symmetry axes, the shape of the surface of the compensation subunit may be circular or regular polygon, etc., and the compensation subunit may be used to resonate the fundamental frequency band, so that the reference subunit may resonate both the fundamental frequency band and the harmonic band, and the bandwidth of the transceiver signal is improved.

In one possible implementation, the width of the array is less than 1.5 times the operating wavelength of the transducer. Thereby enabling the array to receive signals in the fundamental frequency band and the harmonic band. The width is understood to be the width of the substrate of the transducer, typically the side parallel to the shorter axis of symmetry, and typically the width of the array of upper electrodes is as close as possible to the width of the substrate when the upper electrodes are fabricated, to increase the sensitivity of the array that the substrate can accommodate and to avoid wasting area of the substrate.

For ease of understanding, the specific structure of the various transducers provided herein is exemplified below by a PMUT (the transducers may be referred to as PMUT transducers), and the PMUTs referred to below may be replaced by CMUTs or other transducer elements.

Scene one, symmetrically arranged PMUT transducer

By way of example, another transducer configuration provided herein may be as shown in fig. 7.

First, the present application provides a transducer that can include multiple sized PMUT cells coupled in an array arrangement on a substrate. As shown in fig. 7, the PMUT cells may be divided into a reference subcell 701 and a compensation subcell 702, arranged in an array on a substrate 703.

Specifically, the PMUT transducer monolithic structure provided by the present application may include four portions of a substrate, a bottom electrode (lower electrode), a piezoelectric layer, and an upper electrode. The cross section of each PMUT cell along the x-axis and y-axis can be seen in fig. 8, where the upper electrode of each cell is divided into two parts, i.e., an inner electrode and an outer electrode, and the inner electrode and the outer electrode are segmented electrodes.

The substrate material can be silicon or glass or organic polymer, and the substrate is etched to generate a cavity structure, so that the structure at the upper part of the cavity can vibrate conveniently; the lower electrode and the upper electrode are used for providing an excitation signal for the piezoelectric layer or collecting a charge signal generated by the stress action of the piezoelectric layer, and the materials of the lower electrode and the upper electrode can be various conductive materials including a metal material Al, au, ag, pt, cu, mo, ti and the like or some conductive polymer materials and the like; the piezoelectric layer material mainly comprises AlN and an alloy material (Sc) _x Al _1-x N), znO and alloy material (V) _x Zn _1-x O), PZT, and alloy materials (PLZT, PNZT), KNN (K) _x Na _1-x NbO ₃ ) The PMN-PT, PVDF or PVDF-TRFE and the like can be specifically selected according to the actual application scene.

The PMUT unit can be divided into a reference subunit and a compensation subunit according to the size, the reference subunit and the compensation subunit are required to be arranged in a central symmetry manner, the intervals between the boundaries of the subunits are possibly close (such as the nearest distance according to the manufacturing process), and the upper limit is generally 1.5 times of fundamental frequency wavelength; the overall size of the array is such that it is less than 1.5 wavelengths in the x-axis or y-axis direction.

The PMUT unit coupling structures with different sizes can achieve the effects of fundamental frequency large bandwidth and harmonic reception simultaneously. For example, as a result of simulation of PMUT cell geometry in fig. 9. Obviously, by coupling PMUT units with different sizes, the staggered coupling of each resonance peak of different subunits is realized in a fundamental frequency section to achieve the complementary effect of the peak and the trough, so that the effect of large bandwidth of the fundamental frequency is obtained by coupling multiple resonance peaks; meanwhile, the high-order modes of each subunit are designed to be near the frequency doubling of the fundamental frequency center frequency, so that the function of harmonic wave receiving is realized.

Specifically, taking a rectangular PMUT cell as an example, each of the rectangular PMUT cells may be referred to asThe geometric structure characteristics are summarized by a characteristic frequency calculation formula of the order mode. In the following formula, f ₀ Is the characteristic frequency of the first-order mode, f _m,1 The characteristic frequency of the m-order mode along the long side direction is L, k, the length-width ratio, T, the bending rigidity of the diaphragm and sigma, the surface density.

/>

Starting from the resonance coupling effect of each subunit, one type of subunit needs to have at least one resonance peak, namely a reference subunit, in the fundamental frequency section and the harmonic wave section respectively, and the other type of subunit needs to have at least one resonance peak, namely a compensation subunit, in the fundamental frequency section and/or the harmonic wave section respectively. As can be seen from equation 2, the larger the aspect ratio k, the closer the characteristic frequency of the higher order mode is to the characteristic frequency of the first order mode, so as to ensure that the reference subunit has more modes in the fundamental frequency and harmonic band than the compensation subunit, and the aspect ratio of the reference subunit is not smaller than the aspect ratio of the compensation subunit.

In general, to ensure harmonic reception, at least the third order mode of the reference subunit is required to be located at the frequency doubling of the first order mode, i.e. f _3,1 ＝2f ₀ Can be obtainedTherefore the aspect ratio of the reference subunit>

In addition, to achieve effective coupling between the reference subunit and the compensation subunit, the first-order resonance peak of the compensation subunit should be located near the first-order resonance peak of the reference subunit, as can be obtained by equation 1, where the first-order resonance frequency of the rectangular PMUT unit is mainly determined by the length (i.e., width) of the short side under the condition that the types and thicknesses of the materials of the layers of the PMUT are determined (i.e., T and σ are fixed), the first-order resonance frequency of the compensation subunit is set to be located between the first-order and third-order frequencies of the reference subunit, and k=1 is taken, where the width of the available compensation subunit is close to the width of the reference subunit, for example, the difference is within ±45%.

Thus, the geometry of the PMUT cell surface provided herein is characterized by: the PMUT units with different sizes are divided into a reference subunit and a compensation subunit, wherein the aspect ratio of the reference subunit is larger than that of the compensation subunitAnd the length-width ratio of the reference subunit is more than or equal to that of the compensation subunit, and the width of the compensation subunit is similar to that of the reference subunit (within +/-45%).

In addition, in order to ensure the z-axis symmetric directivity of the PMUT array radiation sound field, the arrangement of the reference subunit and the compensation subunit needs to meet the central symmetric distribution condition. In addition, in order to improve the utilization of the whole area of the array (i.e. the diaphragm area/the whole area of the array), the spacing between the different PMUT cells needs to be as small as possible, and the specific range can be determined according to the process error.

And under the condition that the whole size of the array is smaller than 1.5 times of wavelength in one direction of x or y, the number of the reference subunits can be increased, namely a plurality of reference subunits can be arranged, and the compensation subunit can also comprise a plurality of PMUT units with different length-width ratios or different widths.

Secondly, the upper electrode of the PMUT unit provided by the application can be arranged into a plurality of block electrodes and can be divided into an inner electrode and an outer electrode, so that the multi-mode PMUT unit has higher receiving sensitivity in all modes. For example, the effect of simulating the stress distribution of different modes of the PMUT cell provided in the present application may refer to fig. 10.

Specifically, during the vibration process of the PMUT diaphragm, two areas of tensile (such as positive stress) stress and compressive (such as negative stress) stress exist on the diaphragm. The polarities of the charges generated in the two types of areas are opposite, and if one electrode covers the tensile stress area and the compressive stress area at the same time, the charges generated by the piezoelectric material can cancel each other, so that the receiving sensitivity is sacrificed. Therefore, the segmented electrode is divided into the inner electrode and the outer electrode, and compared with a whole block of received signals, the inner and outer segmented electrodes provided by the application can be expanded to give consideration to multiple modes only aiming at a single mode, as shown in fig. 10, the stress distribution of the rectangular PMUT in one, three and five modes is large (only one, three and five modes are taken as an example here and can be replaced by other modes), and the electrode is designed according to the stress distribution of each mode, so that the receiving sensitivity of the corresponding mode can be generally guaranteed only while the receiving sensitivity of the other modes is sacrificed.

And the area with the largest modal stress amplitude and consistent sign of each order is taken as a receiving electrode, namely a central part (called a central electrode). The receiving sensitivity of the first, third and fifth modes can be considered by adopting the central electrode as the receiving electrode, and meanwhile, the receiving sensitivity of the central electrode is higher than the receiving sensitivity designed according to the stress distribution of each mode because the electrode position is the stress maximum part of each mode.

In addition, the stress distribution of each order mode can find that the stress of the central part of the external electrode is also consistent, so that the external electrode distribution design is additionally introduced, and the receiving capacitance can be further increased through differential receiving of the internal electrode and the external electrode, and the parasitic interference resistance is improved.

As shown in fig. 10, the difference in resonant peak frequencies between the center electrode and the bulk electrode is typically caused by the fact that the center electrode and the edge electrode are not uniformly affected by the modal stresses of one, three and five orders.

Specifically, for example, as shown in fig. 11, the transceiver setting circuit for the inner and outer electrodes may need to excite the whole electrode in the transmitting mode, and at the receiving time, the center electrode is adopted for receiving, and the switching of the transmitting and receiving electrodes is realized by the transceiver switching switch as shown in fig. 11, and the inner and outer electrodes adopt the inverse excitation and the differential reception. The upper electrode can be divided into an inner electrode and an outer electrode according to the tensile stress and compressive stress distribution of the PMUT first-order mode; the inner electrode and the outer electrode are respectively provided with a geometric center part as a receiving area, wherein the length of the center electrode of the inner electrode is 1/9-1/3 of the whole length of the inner electrode, and the length of the center electrode can be generally determined according to a mode, for example, the center electrode of a fifth-order mode is 1/5; the center electrode of the outer electrode is equal in length to the center electrode of the inner electrode. The PMUT unit provided by the application is excited by the whole electrode during transmitting, and the resonance peak frequency of the PMUT unit is consistent with that of the whole electrode, so that the transmitting resonance peak and the receiving resonance peak can be avoided by adopting the central electrode for receiving, and the complementation of transmitting and receiving frequency bands can be realized, so that the receiving and transmitting comprehensive bandwidth is increased.

Scene two, elliptic transducer

The shapes of the PMUT cells may include, among others, some shapes having an aspect ratio, i.e., having a long axis and a short axis, such as ellipses, polygons (diamond to n-sided), and irregular geometries where the long and short axes are formed by arbitrary curves.

In this embodiment, taking an ellipse as an example, the comparison of the reception bands of an elliptical PMUT cell and a rectangular PMUT cell may be as shown in fig. 12. Obviously, the elliptical structure is similar to the rectangular structure and also has a multi-modal character. Further, the length-width ratio characteristic of each order mode of the elliptical PMUT can be adjusted, so that the elliptical structure can achieve the same or similar effect in the rectangular PMUT through size adjustment.

In addition, since the frequency difference between the modes of each order of the ellipse is larger than that of the rectangular structure (i.e. the ellipse has only two modes in the frequency sweep range of 2-8MHz and the rectangle has three modes under the same aspect ratio in fig. 10), the size characteristic points (such as the aspect ratio is larger than that of the rectangular structure) of the rectangular PMUT cell) Elliptical structural features are contemplated. Other dimensional feature points related to the rectangular PMUT structure are also applicable to ellipses, including intervals and numbers among units, central symmetry arrangement modes, block internal and external electrode designs and the like, and are not repeated here.

Scene three, circular compensation subunit

In an alternative embodiment, the reference subunit may be a PMUT having a shape with an aspect ratio, and the compensation subunit may be a geometric structure without aspect ratio structural features, such as a circle, square, or regular polygon.

Taking the circular compensation subunit as an example, the structure of coupling the circular compensation subunit and the rectangular reference subunit and its simulation effect can be referred to fig. 13. The rectangular PMUT may be considered a reference subunit and the circular PMUT may be considered a compensation subunit. Trough compensation between first-order modes and third-order modes of the rectangular PMUT can be realized through circular PMUT units with different sizes, but because the high-order modes of the circular PMUT are far away from the fundamental frequency mode and are not adjustable, the frequency ratio of the first two-order modes is 3.9 according to a calculation formula of resonance frequencies of different modes of the circular PMUT. Circular PMUT cells can only be used to receive fundamental frequency band waves, but not harmonics. Therefore, in the embodiment of the application, the fundamental frequency large bandwidth can be realized through the reference subunit and the compensation subunit, and the harmonic receiving function is realized only through the reference subunit.

Scene four, upper electrode asymmetric arrangement

In one of the foregoing scenarios, the block design of the upper electrode is based on maximizing the receiving sensitivity of each mode, and is mainly aimed at the low-order modes, such as the first, third and fifth modes, and the embodiment further expands the block design of the electrode from the viewpoint of integrating the receiving sensitivity and the bandwidth.

The embodiment of the application further provides another transducer, wherein the upper electrode of the PMUT cell in the transducer can be divided into a plurality of segmented electrodes, the plurality of segmented electrodes are arranged asymmetrically, and the number of the segmented electrodes of each PMUT cell is related to the required receiving mode, if the required mode is higher, the number of the segmented electrodes is larger.

For example, referring to fig. 14, a schematic structural diagram of another transducer provided herein, fig. 15 and 16 are effects of transmit sensitivity and receive sensitivity based on asymmetrically arranged PMUT cells.

The difference from the transducer unit mentioned in scenario one above is that the upper electrodes are arranged asymmetrically along a central axis parallel to the broadside. By asymmetrically blocking electrodes, a large bandwidth can be formed in a single size PMUT cell or an array of PMUT cells.

In this embodiment, taking a ninth-order mode as an example, the segmented electrode may be set according to stress distribution of the ninth-order mode, so as to increase transmit-receive sensitivity of the ninth-order mode, thereby solving the problem that the transmit-receive sensitivity of the ninth-order mode is lower and cannot be coupled with the third, fifth and seventh-order modes at-6 dB under the condition of excitation and reception of the traditional monolithic electrode structure.

First, the number of segmented electrodes depends on the required optimized mode order n=9, i.e. the number of segmented electrodes is equal to (n+1)/2=5 blocks. The width of each electrode is consistent or close to that of the previous scene along the width direction, and the dimension of each electrode is taken as the boundary between the internal stress and the external stress of the first-order mode. In the length direction, if the design is completely according to the stress distribution of the nine-order modes, the length of each electrode is 1/9 of the whole length of the inner electrode, which improves the sensitivity of the nine-order modes but sacrifices the sensitivity of other modes (three, five and seven), so that the whole area of the segmented electrode is selected to be basically consistent with or close to the whole electrode area without sacrificing the sensitivity of the other modes. Wherein the gap between the segmented electrodes is taken to minimize the difference from the area of the whole electrode. For the size of each electrode, based on the optimization result of simulation, the size b of the center electrode is generally selected to be near the optimal size a of the nine-order mode (1/n of the inner electrode size) (b=a-1.8 a), the electrode size (b-2 b) adjacent to the center electrode is larger than the center electrode size, and the peripheral electrode size (< b) is smaller than the center electrode size.

In order to improve the sensitivity of the receiving sensitivity at the trough position between the resonance peaks of each order in the arrangement of the segmented electrodes so as to realize better coupling of each order mode within the range of-6 dB, the embodiment proposes that the segmented electrodes are asymmetrically arranged along the central axis parallel to the width. As shown in fig. 15, the common segmented electrodes are symmetrically distributed along the central axes x and y, while the asymmetric electrodes of the present embodiment are symmetrically distributed along the x-axis only and asymmetrically distributed along the y-axis, the implementation effect can refer to the receiving sensitivity curve diagram on the right side in fig. 15, and the asymmetric electrode design can improve the sensitivity between the third fifth order and the fifth seventh order. In terms of implementation, the asymmetric electrode of this embodiment is implemented on the basis of the above-mentioned segmented electrodes, that is, the positions of the segmented electrodes 1 and 2 in fig. 16 are exchanged to implement asymmetric arrangement.

In the working mode, the segmented asymmetric electrode of the embodiment is similar to the segmented electrode in the first scene, and is transmitted by a whole electrode and received by a central electrode. For example, the center 3 electrodes may be selected for receiving, and in this embodiment, the center 3 electrodes are shorted by the pad connection line for convenience of wire leading, where the width of the pad connection line should be reduced as much as possible, so as to reduce the area of the pad connection line as much as possible.

Thus, in the present embodiment, electrode segmentation divides the electrode into (n+1)/2 blocks according to the highest order (as represented by n order, n is typically an odd number) modality utilized; the sizes of the segmented electrodes are different, wherein the area of the central electrode is smaller than the area of an electrode adjacent to the central electrode, the area of the central electrode is larger than the area of the edge electrode, and the whole area and the coverage area of the segmented electrode are basically close to those of the whole electrode (based on the first-order modal stress distribution); the segmented electrodes are asymmetrically distributed along a central axis parallel to the short sides; when excited, all the block electrodes work simultaneously, and when received, only the middle part of the electrodes work. The method can reduce the receiving sensitivity difference of the odd-order and even-order modes of the multimode PMUT, and is convenient for coupling a plurality of modes within-6 dB, thereby realizing large bandwidth.

Scene five and large-scale array

Various structures of the PMUT transducer provided in the present application have been described, and on the basis of these, a larger-scale array structure can be implemented, as shown in fig. 17. In fig. 17, (a), (b) and (c) are array expansion forms of the first embodiment, specifically, in fig. 17, (a) is expansion of the first embodiment along the y direction, and of course, the expansion direction may also be the x direction, provided that the feature size of the expansion direction is smaller than 1.5 times of wavelength, and the number of the repeating units in the expansion direction may be set according to the limitation of the actual application scene on the overall size of the device. Fig. 17 (b) and (c) are derivative and array expansion in the direction of cell arrangement in the first embodiment, the limitation of the arrangement mode in the first embodiment is center symmetry, fig. 17 (b) and (c) are another center symmetry arrangement mode, namely, the orthogonal arrangement of the reference subunit and the compensation subunit is changed into parallel arrangement, and the difference between fig. 17 (b) and (c) is that the compensation subunit and the reference subunit in the fig. b are aligned in the center and the fig. 17 (c) is staggered arrangement. In fig. 17, (d) and (e) are array expansion forms of the third and fourth embodiments, respectively, and of course, similar to the first scenario, the arrangement of the units may be other centrosymmetric forms, which are not described herein again. In fig. 17 (f), the expansion form of the PMUT array in the fourth scenario is shown in the foregoing, and after the segmented asymmetric electrode is adopted, the PMUT array may be formed by PMUT cells with a single size to achieve a large bandwidth effect, and in addition, the arrangement form of the array is symmetrical along the geometric center, and may also be expanded into an axisymmetric structure.

For example, in the imaging system provided in the present application, a plurality of transducers are provided in a probe, as shown in fig. 18, the plurality of transducers being arranged in an array. The plurality of transducers form a plurality of channels for transmitting and acquiring echo signals, thereby increasing the imaging area.

Therefore, the transducer provided by the embodiment of the application can be applied to a scene needing large-scale detection, can realize detection with high sensitivity and large area, and can generate an ultrasonic image with higher resolution through the large-bandwidth transducer provided by the application when being applied to an ultrasonic imaging scene.

The foregoing description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, since it is intended that all modifications, equivalents, improvements, etc. that fall within the spirit and scope of the invention.

Claims

1. A transducer, comprising: a substrate and a plurality of transduction units arranged in an array on the substrate;

each of the transduction units includes an upper electrode and a lower electrode, upon emitting an acoustic wave, an excitation electric signal is applied to the upper electrode and the lower electrode to vibrate a diaphragm to generate an acoustic wave, upon receiving the acoustic wave, the transduction unit is deformed to generate an electric charge between the upper electrode and the lower electrode, and a reception electric signal for generating an output image is outputted through the upper electrode and the lower electrode;

The plurality of transduction units are divided into at least one reference subunit and at least one compensation subunit, the length-to-width ratio of the reference subunit is not smaller than that of the compensation subunit, the length-to-width ratio of the reference subunit is not smaller than a first threshold, so that the reference subunit is used for generating resonance in a fundamental frequency section and a harmonic wave section, the compensation subunit generates resonance in the fundamental frequency section, the first threshold is obtained according to the fundamental frequency section and the harmonic wave section, and the dimension of the transduction unit is calculated according to the frequency for generating resonance.

2. The transducer according to claim 1, wherein the first threshold is

3. The transducer according to claim 1 or 2, wherein the compensation subunit is also resonating in the harmonic section.

4. A transducer according to any of claims 1-3, wherein the upper electrode comprises a plurality of segmented electrodes, the received electrical signal being acquired by a central electrode of the plurality of segmented electrodes when an electrical charge is generated between the upper electrode and the lower electrode, the central electrode comprising at least one segmented electrode closest to a center point of the upper electrode.

5. The transducer of claim 4, wherein the transducer comprises a transducer body,

exciting each of the plurality of segmented electrodes when transmitting sound waves;

when receiving an acoustic wave, the received electrical signal is acquired through the center electrode.

6. Transducer according to claim 4 or 5, wherein the plurality of segmented electrodes is divided into at least one inner electrode and/or at least one outer electrode, the at least one outer electrode surrounding the at least one inner electrode;

when transmitting sound waves, adopting inverse excitation to the at least one external electrode and the at least one internal electrode;

when receiving sound waves, differential reception is adopted for the center electrode in the at least one outer electrode and the center electrode in the at least one inner electrode.

7. The transducer of any of claims 4-6, wherein the plurality of segmented electrodes are symmetrically arranged.

8. The transducer of any of claims 1-7, wherein the transducer comprises a transducer array,

the plurality of transducers are arranged in a central symmetry on the substrate.

9. The transducer of any of claims 1-8, wherein the distance between adjacent transducing elements is no more than 1.5 times the fundamental wavelength.

10. The transducer of any of claims 1-9, wherein the transduction unit comprises a micromechanical piezoelectric ultrasonic transducer PMUT cell, and a piezoelectric sensing layer is further disposed between the upper electrode and the lower electrode in each PMUT cell.

11. The transducer according to any of claims 1-9, wherein the transduction unit comprises a micromechanical capacitive ultrasound transducer CMUT unit, wherein an insulating layer is comprised between the upper electrode and the lower electrode, and wherein a cavity structure is further provided between the upper electrode and the lower electrode.

12. The transducer of any of claims 1-11, wherein the shape of the plurality of transducing cells includes at least one of a rectangle, an ellipse, or a polygon having at least two central symmetry axes, and the aspect ratio of the reference subunit is greater than 1.

13. The transducer of claim 12, wherein the shape of the at least one compensation subunit surface comprises a circle or regular polygon having an aspect ratio equal to 1.

14. The transducer of any of claims 1-13, wherein the width of the array is less than 1.5 times the operating wavelength of the transducer.

15. A transducer, comprising: a substrate and a plurality of transduction units arranged on the substrate;

the aspect ratio of each transduction unit is larger than 1, and the upper electrode of each transduction unit comprises a plurality of segmented electrodes which are asymmetrically arranged.

16. The transducer of claim 15, wherein the transducer comprises a transducer,

when receiving sound waves, the received electric signals are acquired through a central electrode arranged on the transducer, wherein the central electrode comprises at least one segmented electrode closest to the central point of the upper electrode.

17. An imaging system, comprising: a probe and a processor;

providing at least one transducer according to any one of claims 1-16 in the probe;

the probe is used for transmitting ultrasonic waves to a target area and receiving ultrasonic echoes returned by the target area so as to obtain ultrasonic echo data;

the processor is used for generating an ultrasonic image according to the ultrasonic echo data.

18. The imaging system of claim 17, wherein the imaging system further comprises:

and the display is used for displaying the ultrasonic image.

19. An imaging system according to claim 17 or 18, wherein a plurality of transducers are provided in the probe, the plurality of transducers being arranged in an array.