阅读说明：本技术 基于Helmholtz共振腔的可调频超声传感器阵列 (Frequency-adjustable ultrasonic sensor array based on Helmholtz resonant cavity ) 是由 孙成亮 王磊 吴志鹏 朱伟 胡博豪 林炳辉 周禹 于 2019-08-15 设计创作，主要内容包括：本发明涉及一种基于Helmholtz共振腔的可调频超声传感器阵列,包括基材、布设于所述基材上的超声发射装置和声波接收装置,所述声波接收装置包括声学传感器以及设置在所述声学传感器上的Helmholtz共振腔。本发明将超声发射装置和接收装置布置在同一个晶片上,超声发射装置中的声学传感器和声波接收装置中的Helmholtz共振腔的共振频率一致,声波接收装置中声学传感器的共振频率高于或低于前两者的共振频率,可以避免阵列单元之间的串扰。(The invention relates to a frequency-adjustable ultrasonic sensor array based on a Helmholtz resonant cavity, which comprises a substrate, an ultrasonic transmitting device and a sound wave receiving device, wherein the ultrasonic transmitting device and the sound wave receiving device are arranged on the substrate, and the sound wave receiving device comprises an acoustic sensor and the Helmholtz resonant cavity arranged on the acoustic sensor. According to the invention, the ultrasonic transmitting device and the ultrasonic receiving device are arranged on the same wafer, the resonance frequencies of the acoustic sensor in the ultrasonic transmitting device and the Helmholtz resonant cavity in the acoustic wave receiving device are consistent, and the resonance frequency of the acoustic sensor in the acoustic wave receiving device is higher or lower than the resonance frequencies of the acoustic sensor and the Helmholtz resonant cavity, so that crosstalk between array units can be avoided.)

1. The utility model provides an adjustable frequency ultrasonic sensor array based on Helmholtz resonant cavity which characterized in that, includes the substrate, lays ultrasonic transmitter and sound wave receiving arrangement on the substrate, sound wave receiving arrangement includes acoustic sensor and sets up Helmholtz resonant cavity on the acoustic sensor.

2. The Helmholtz cavity based tunable ultrasonic sensor array as defined in claim 1, wherein said ultrasonic transmitter means has a resonance frequency corresponding to a resonance frequency of said Helmholtz cavity, and said acoustic sensors in said acoustic receiver means have a resonance frequency different from said resonance frequency of said ultrasonic transmitter means and said Helmholtz cavity.

3. The Helmholtz-resonator-based tunable ultrasonic sensor array of claim 1, wherein the Helmholtz resonator comprises a cavity and a through hole communicating with the cavity, the Helmholtz resonator is disposed on the acoustic sensor and the cavity is in contact connection with a surface of the acoustic sensor.

4. The Helmholtz-resonator-based tunable ultrasonic sensor array of claim 3, wherein the cavity is formed by a hollow silicon structure disposed on the surface of the acoustic sensor and enclosing the surface of the acoustic sensor, the through-hole being disposed on the silicon structure.

5. The Helmholtz-resonator-based tunable ultrasonic sensor array of claim 4, wherein the size, number, shape and location of the through holes are determined by the resonant frequency of the Helmholtz resonator.

6. The Helmholtz-resonant-cavity-based adjustable-frequency acoustic wave receiving device of claim 1, wherein said acoustic sensor is a piezoelectric ultrasonic transducer or a capacitive ultrasonic transducer.

7. The Helmholtz resonant cavity-based tunable acoustic wave receiving device as claimed in claim 6, wherein said piezoelectric ultrasonic transducer is of a sandwich structure or a bimorph structure.

Technical Field

The invention relates to the technical field of sensors, in particular to a frequency-adjustable ultrasonic sensor array based on a Helmholtz resonant cavity.

Background

An ultrasonic transducer is a transducing element that can be used to both transmit and receive ultrasonic waves, which is the core of an acoustic sensor. When the transducer works in a transmitting mode, electric energy is converted into vibration of the transducer through electrostatic force or inverse piezoelectric effect so as to radiate sound waves outwards; when the transducer works in a receiving mode, sound pressure acts on the surface of the transducer to enable the transducer to vibrate, and the transducer converts the vibration into an electric signal. At present, the most widely used ultrasonic sensor is mainly based on a piezoelectric transducer, the piezoelectric transducer mainly utilizes a thickness vibration mode of piezoelectric ceramics to generate ultrasonic waves, and because the resonant frequency of the thickness mode is only related to the thickness of the transducer, the ultrasonic transducers with different resonant frequencies are difficult to manufacture on the same plane. When the high-frequency-resistant high-frequency. The ultrasonic transducer (MEMS ultrasonic transducer) manufactured by the micromachining technology vibrates in a bending mode, has a vibrating membrane with lower rigidity, has lower acoustic impedance, and can be better coupled with gas and liquid. And the resonant frequency is controlled by the in-plane dimension, so that the requirement on the machining precision is low. With the gradual maturity of the MEMS ultrasonic transducer technology, the technology of the ultrasonic sensor tends to turn to the MEMS ultrasonic transducer because of its advantages of high performance, low cost and easy realization of mass production. The MEMS ultrasonic transducer mainly comprises two capacitance type (cMUT) and piezoelectric type (pMUT), the sensitivity of the pMUT is slightly lower than that of the cMUT, but the cMUT needs to provide bias voltage and a tiny air gap is arranged between capacitance polar plates, adhesion is easily formed, and the pMUT has the advantages of simple structure and high transduction efficiency of transduction materials, but the manufacture of the pMUT is more complex.

Patent CN109196671A discloses a piezoelectric micromachined ultrasonic transducer (pMUT) that reduces acoustic diffraction by adding a high acoustic velocity material to the transducer to generate high frequencies. The PMUT has a low quality factor, providing shorter start-up and shut-down times, to enable better suppression of spurious reflections through time-gating. Patent CN107394036A discloses an electrode configuration of pMUT and pMUT transducer arrays, which makes the transducer have different modes of action by using a dual electrode or multiple electrodes in the upper electrode, by applying the same or different electrical signals to the different electrodes. Patent CN106660074A discloses a piezoelectric ultrasonic transducer and a process, which uses an anchoring structure and a mechanical layer to form a cavity, adjusts the position of the central axis of the stacked layers through the mechanical layer, thereby allowing the stacked layers to vibrate in bending, and adjusts the parameters of resonance frequency, quality factor Q, etc. through the use of a concave portion. Overall, the current pMUT improvements are mainly directed to the electrode shape thereof, the addition of materials to the outside, and the like, but have a limited effect on improving the pMUT energy conversion efficiency.

Patent CN103240220B discloses a piezoelectric array ultrasonic transducer, which adopts the arrangement of common lower electrode and array upper electrode to make the vibrating membrane and piezoelectric membrane at the bottom of each array element have the same or different thickness, so that the array elements can work under the same or different working frequencies. Patent CN108284054A discloses a piezoelectric ceramic ultrasonic linear phased array transducer and a preparation method thereof, and a transducer array with high resolution and large detection depth is prepared by technologies such as array cutting, thinning, micro-machining electrode deposition, patterning and the like. The existing sensor array has a serious crosstalk problem, and as the resonance frequencies of the sensors at the transmitting end and the receiving end are close, the receiving end inevitably generates interference electric signals when transmitting ultrasonic waves, so that the performance of the sensor array is influenced; in addition, each array element in the array operates at the same operating frequency, the bandwidth is narrow, and the sensitivity of the sensor array needs to be improved.

Generally, the receiving unit of the sensor array has the defects of low sensitivity, low sound-electricity energy conversion efficiency, non-adjustable frequency and the like, and the sensor array has the limitations of serious crosstalk, narrow bandwidth and the like.

disclosure of Invention

the invention aims to provide a frequency-adjustable ultrasonic sensor array based on a Helmholtz resonant cavity, which has high sensitivity and high acoustoelectric energy conversion efficiency and can avoid crosstalk among array units.

The scheme adopted by the invention for solving the technical problems is as follows:

The utility model provides an adjustable frequency ultrasonic sensor array based on Helmholtz resonant cavity, includes the substrate, lays ultrasonic emission device and sound wave receiving arrangement on the substrate, sound wave receiving arrangement includes acoustic sensor and sets up Helmholtz resonant cavity on the acoustic sensor.

further, the resonance frequency of the ultrasonic transmitting device is consistent with the resonance frequency of the Helmholtz resonant cavity, and the resonance frequency of the acoustic sensor in the acoustic wave receiving device is different from the resonance frequencies of the ultrasonic transmitting device and the Helmholtz resonant cavity.

Further, the Helmholtz resonant cavity comprises a cavity and a through hole communicated with the cavity, and is arranged on the acoustic sensor, and the cavity is in contact connection with the surface of the acoustic sensor.

further, the cavity is formed by enclosing a hollow silicon structure arranged on the surface of the acoustic sensor and the surface of the acoustic sensor, and the through hole is arranged on the silicon structure.

Further, the size, number, shape and position of the through holes are determined by the resonance frequency of the Helmholtz resonant cavity.

further, the acoustic sensor is a piezoelectric ultrasonic transducer or a capacitive ultrasonic transducer.

further, the piezoelectric ultrasonic transducer is of a sandwich structure or a bimorph structure.

Compared with the prior art, the invention has at least the following beneficial effects:

1) The MEMS acoustic sensor and the Helmholtz resonant cavity are combined to form an array acoustic wave receiving unit; when the sound wave receiving device receives the emission echo, the frequency of the sound wave can be set to be consistent with the resonance frequency of the Helmholtz resonant cavity in advance, the sound wave is transmitted to the through hole to cause the medium in the cavity to resonate and consume the sound wave energy of the resonance frequency, so that the sound pressure in the cavity is increased, the sound pressure acting on the surface of the MEMS acoustic sensor is improved, and the electric signal generated by the MEMS acoustic sensor is increased;

2) The invention realizes the adjustment of the resonance frequency of the Helmholtz resonant cavity by adjusting the size, shape and position of the through hole formed on the silicon structure;

3) The ultrasonic transmitting device and the sound wave receiving device are arranged on the same wafer, the resonance frequency of the acoustic sensor in the ultrasonic transmitting device is consistent with that of the Helmholtz resonant cavity in the sound wave receiving device, and the resonance frequency of the acoustic sensor in the sound wave receiving device is higher or lower than that of the acoustic sensor in the sound wave receiving device, so that crosstalk between array units can be avoided.

Drawings

FIG. 1 is a cross-sectional view of an array structure in accordance with an embodiment of the present invention, in which only one transmitting unit and only one receiving unit are arranged;

FIG. 2 shows an arrangement of arrays according to an embodiment of the present invention;

FIG. 3 is a cross-sectional view of a receiving unit with a sandwich structure according to an embodiment of the present invention;

FIG. 4 is a cross-sectional view of a receiving unit with an electrode of a sandwich structure according to an embodiment of the present invention;

FIG. 5 is a cross-sectional view of a receiver unit employing bimorph lead-out electrodes in accordance with an embodiment of the present invention;

Fig. 6 is a cross-sectional view of a receiving unit using a capacitive ultrasonic transducer according to an embodiment of the present invention.

Detailed Description

The following examples are provided to further illustrate the present invention for better understanding, but the present invention is not limited to the following examples.

Referring to fig. 1 and 2, the present invention provides a tunable ultrasonic transducer array based on a Helmholtz resonant cavity, which includes a substrate 1, an ultrasonic transmitter 2 disposed on the substrate 1, and a sound receiver 3. In this embodiment, the ultrasonic transmitter 2 and the acoustic wave receiver 3 are disposed on the same wafer, and the two devices may be disposed in any manner, and the number, the spacing, and the arrangement of the two devices may be selected according to specific situations. The ultrasonic emission device 2 is also flexible to select, and can be a piezoelectric ultrasonic transducer or a capacitive ultrasonic transducer. The acoustic wave receiving device 3 includes a MEMS acoustic sensor 30 and a Helmholtz resonator 31 disposed on the MEMS acoustic sensor 30, wherein the MEMS acoustic sensor 30 is for receiving acoustic pressure generated when the Helmholtz resonator 31 resonates. The MEMS acoustic sensor 30 can also take various forms, as shown collectively in fig. 3-6, and the MEMS acoustic sensor 30 can be either a piezoelectric or a capacitive ultrasonic transducer, or any other form of ultrasonic transducer. When the MEMS acoustic sensor 30 is a piezoelectric ultrasonic transducer, it may be a conventional sandwich structure or a bimorph structure. Of course, the shape of the MEMS acoustic sensor 30 can also be in various forms, such as circular, square, rectangular, hexagonal, or other polygonal shapes.

The Helmholtz resonator 31 includes a hollow silicon structure 310 disposed on a surface of the MEMS acoustic sensor 30, a cavity 311 formed by the hollow silicon structure 310 and the surface of the MEMS acoustic sensor 30, and a through hole 312 disposed on the silicon structure 310 and communicating with the cavity 311. The through hole 312 communicates the external atmosphere with the cavity 311, thereby facilitating the propagation and resonance of the acoustic wave. In addition, the cavity 311 is in contact connection with the surface of the MEMS acoustic sensor 30, so that the sound pressure amplified by the Helmholtz resonator 31 can directly act on the MEMS acoustic sensor 30, which is beneficial to improving the acoustoelectric energy conversion efficiency of the acoustic sensor.

in the present invention, in order to avoid crosstalk between array units, the resonance frequencies of the acoustic sensors in the ultrasonic transmission device 2 and the Helmholtz resonator 31 in the acoustic wave receiving device 3 are the same, and the resonance frequency of the MEMS acoustic sensor 30 in the acoustic wave receiving device 3 is higher or lower than the resonance frequencies of the acoustic sensors in the ultrasonic transmission device 2 and the Helmholtz resonator 31, so that crosstalk between array units can be avoided. The MEMS acoustic sensor 30 in the acoustic wave receiving device 3 is configured to receive an acoustic wave in the cavity when the Helmholtz resonant cavity 31 resonates, and when the frequency of the acoustic wave is consistent with the resonant frequency of the Helmholtz resonant cavity 31 when the transmitted ultrasonic echo is received, the acoustic wave propagates to the through hole 312 to cause the medium in the cavity 311 to resonate and consume the acoustic wave energy of the resonant frequency, so as to increase the acoustic pressure in the cavity, and the amplified acoustic pressure acts on the surface of the MEMS acoustic sensor 30 in the receiving device, so as to improve the acoustic-electric energy conversion efficiency of the acoustic sensor.

According to the formula of the resonance frequency of the Helmholtz resonant cavity:

In the formula, c is the sound velocity in the medium, S is the area of the through hole, t is the height of the through hole, d is the diameter of the through hole, and V is the volume of the cavity. Based on the above formula, we can adjust the resonant frequency of the Helmholtz resonant cavity 31 by adjusting the size, number, shape and arrangement position of the through holes 312. That is, in practical use, the size, number, shape and arrangement position of the through holes 312 are determined according to the required resonance frequency of the Helmholtz resonant cavity 31. For example, when the resonance frequency of the Helmholtz resonator 31 is required to coincide with the resonance frequency of the acoustic wave, the size, number, arrangement position, and the like of the through holes 312 may be determined according to the resonance frequency of the acoustic wave.

while the foregoing is directed to the preferred embodiment of the present invention, other and further embodiments of the invention may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.