Three-dimensional omnidirectional transmitting device for acoustic vortex signals

Abstract

The invention discloses a three-dimensional omni-directional transmitting device for acoustic vortex signals, which comprises an acoustic phased array circuit, a planar fan-shaped transducer array, a lower-layer gradient lens, a middle-layer synthesis lens and an upper-layer focusing lens, and is characterized in that an active array phase control method and a passive lens phase modulation method are combined, and a cascade lens design is adopted, so that the three-dimensional omni-directional transmitting device for the acoustic vortex signals is realized. Acoustic waves can be gathered at any position in a three-dimensional space, and acoustic vortex signals with controllable topological charges are generated at any position in the radial direction and the angular direction by means of relative rotation of the lower-layer gradient lens and the middle-layer composite lens. And by utilizing the relative rotation of the middle-layer synthesis lens and the upper-layer focusing lens, an acoustic vortex signal with controllable topological charge is further generated at any position in a three-dimensional space. According to the method, the acoustic vortex signal can be generated quickly and conveniently, so that better signal transmission performance can be provided in acoustic vortex engineering, and the method has obvious advantages in the aspects of complex sound field regulation and flexibility.

Description

Technical Field

[0001] This invention relates to a three-dimensional omnidirectional transmitting device for acoustic vortex signals, belonging to the field of underwater signal transmission and sound field control technology. Background Technology

[0002] Unlike plane waves, vortex sound beams are a special type of sound beam with a helical phase wavefront, a phase singularity at the center of the vortex, and a zero field strength. Mathematically, the unique phase distribution of a vortex sound beam can be expressed as exp( ilφ ) Description, in which l Represents topological loads, φ The azimuth angle is indicated. The concept of vortex beams has provided a completely new research direction for current fields such as sound field manipulation and wave control. Because sound waves involve particle vibration and pressure distribution during propagation through a medium, the energy flow rotation and angular momentum carrying characteristics of vortex beams make it possible to manipulate complex sound field structures. In recent years, with the continuous development of wavefront amplitude and phase manipulation techniques, researchers have deepened their understanding of acoustic vortices. Current theoretical analyses and experimental results both indicate that vortex beams have enormous potential application value in information transmission, non-contact actuation, particle manipulation, and target detection and recognition. These potentials suggest that vortex beams are not only a natural extension of vortex beam theory in the acoustic field, but also a key starting point for promoting modern acoustic research towards high-dimensional manipulation and intelligent acoustics.

[0003] However, the current research on acoustic vortex beams is mainly focused on coaxial transmission, but in practical applications, the transmission center and the vortex center are often not on the same axis, so it is necessary to effectively transmit the energy-concentrated signal to a specific location and adjust the transmission direction freely to construct a safe, flexible and controllable underwater acoustic vortex directional transmission system. Some researchers combined the iterative back propagation algorithm with a transmitter array composed of two 256-element arrays to construct a corresponding vortex acoustic beam at any two-dimensional location in space. However, the large number of array elements will inevitably lead to an increase in cost, and the flexibility of the entire system is poor. To solve this problem, some people proposed introducing additional phase delays into the traditional planar sensor ring array to construct a directional off-axis acoustic vortex by pre-allocating the vortex center position. This method greatly reduces the complexity of the system, but each change in the vortex center requires a recalculation of the phase of the sound source array, and the adjustability and flexibility are poor. Some researchers proposed using a planar reflective phase plate engraved with a spiral groove to convert a normally incident plane wave into a focused vortex acoustic beam. By changing the center of the spiral groove, off-axis directional operation of the focused vortex acoustic beam can also be achieved. By analyzing the main construction methods of the current focused vortex acoustic beam, it can be seen that the construction scheme based on a two-dimensional array usually requires a large number of transducer units, which leads to the need to design a complex phased array circuit structure, resulting in a significant increase in system cost. In addition, when the topological charge of the vortex acoustic beam needs to be changed or the focal point position needs to be adjusted, the phase of all units in the transmitting array needs to be recalibrated, thereby reducing the overall efficiency. In contrast, the construction method based on phase modulation structure does not require a large number of transmitting units, but each phase modulation structure can only generate a single topological charge, and the focal point position is fixed and cannot be adjusted. When the focal point or topological charge needs to be changed, a new structure must be additionally processed, resulting in poor flexibility and adjustability of the overall transmission system. SUMMARY

[0004] The present application is to solve the above-mentioned deficiencies in the prior art, and proposes a three-dimensional omnidirectional acoustic vortex signal transmission device, in order to realize fast and accurate acoustic vortex signal generation, thereby providing a better signal transmission system in the field of underwater acoustic vortex engineering.

[0005] In order to achieve the above-mentioned application purposes, the present application adopts the following technical solutions: The three-dimensional omnidirectional acoustic vortex signal transmission device of the present application is characterized in that it comprises an acoustic phased array circuit, a planar fan-shaped transducer array, a lower gradient lens, a middle layer synthetic lens and an upper layer focusing lens. The acoustic phased array circuit generates N-path programmable delay square wave signals at a fixed operating frequency; after the N-path square wave signals pass through a low-pass filter to filter out high-frequency components, N-path smooth waveform signals are output; after the N-path waveform signals pass through the amplification processing of a wideband power amplifier, N-path sinusoidal signals with adjustable amplitude and phase are output; The planar sector transducer array synthesizes the received N-path sinusoidal signals in the propagation direction along the propagation axis, and radiates target acoustic vortex signals with adjustable topological order; The lower layer gradient lens is nested in the exit surface of the planar sector transducer array, and after the target acoustic vortex signal is subjected to deflection phase modulation, the modulated target acoustic vortex signal is output, and the refractive angle β The modulated target acoustic vortex signal is deflected to one side of the propagation axis for propagation, so as to control the propagation direction of the target acoustic vortex signal; The middle layer synthesis lens is placed at a position with a distance d from the lower layer gradient lens in the direction perpendicular to the exit surface of the planar sector transducer array; after the target acoustic vortex signal propagating on one side of the propagation axis is subjected to phase modulation in the middle layer synthesis lens, the target acoustic vortex signal propagates along another deflection angle β’ away from the propagation axis; The upper layer focusing lens is placed at a position with a distance d from the middle layer synthesis lens in the direction perpendicular to the surface of the middle layer synthesis lens; after the target acoustic vortex signal propagating away from the propagation axis is subjected to phase modulation in the upper layer focusing lens, the target acoustic vortex signal is focused at a fixed focal point position, and the final target acoustic vortex signal is output; The rotation angle of the lower layer gradient lens and the middle layer synthesis lens is in the range of [-π, π]; by adjusting the rotation angle of the lower layer gradient lens and the middle layer synthesis lens, the phase modulation effect between the lower layer gradient lens and the middle layer synthesis lens is changed, and the refractive angle β and the deflection angle of the middle layer synthesis lens are changed β’ , so as to control the propagation direction of the final target acoustic vortex signal; The rotation angle of the middle layer synthesis lens and the upper layer focusing lens is in the range of [-π, π]; by adjusting the rotation angle of the middle layer synthesis lens and the upper layer focusing lens, the phase modulation effect between the middle layer synthesis lens and the upper layer focusing lens is changed, so as to control the focusing direction of the target acoustic vortex signal, and change the focal point position of the final target acoustic vortex signal.

[0006] The three-dimensional omnidirectional emission device for acoustic vortex signals also has the characteristics that: According to the bottom angle α of the lower layer gradient lens and the refractive angle βa linear relationship between the two, the range of the base angle α of the lower gradient lens is determined to be π / 8-π / 6.

[0007] Further, according to the generalized Snell's law of refraction, the phase modulation function of the lower gradient lens is designed by using formula (1) , so as to deflect the phase modulation of the target acoustic vortex signal; (1) In formula (1), b is the gradient phase change rate of the lower gradient lens, and b ∈[25π, 100π]; is the distance between any point on the lower gradient lens and the center of the lower gradient lens, is the azimuth angle of any point on the lower gradient lens, is the polar coordinate of the position of any point on the surface of the lower gradient lens.

[0008] Further, the phase modulation function of the middle synthetic lens is designed by using formula (2) , and is used for phase modulation of the target acoustic vortex signal; (2) In formula (2), represents the imaginary unit, represents the rounding operation, k is the wave number, F 0 is the preset focal length of the middle synthetic lens, and F 0∈[100, 200].

[0009] Further, the phase modulation function of the upper focusing lens is designed by using formula (3) , and is used for phase modulation of the target acoustic vortex signal; (3) Further, the combined phase modulation function of the lower gradient lens and the middle synthetic lens is designed as follows to change the phase modulation effect between the lower gradient lens and the middle synthetic lens: Step a, adjust the rotation angle of the lower gradient lens to After that, the phase modulation function of the lower gradient lens is designed by using formula (4) : (4) Step b, adjust the rotation angle of the middle synthetic lens to After that, the phase modulation function of the middle synthetic lens is designed by using formula (2) : (5) Step c, determine the combined phase modulation effect of the rotated lower layer gradient lens and the middle layer synthetic lens using formula (5) : (6).

[0010] Further, the combined phase modulation function of the middle layer synthetic lens and the upper layer focusing lens is designed as follows to change the phase modulation effect between the middle layer synthetic lens and the upper layer focusing lens: Step a, adjust the rotation angle of the middle layer gradient lens to After that, the phase modulation function of the middle layer synthetic lens is designed using formula (2) : (7) Step b, adjust the rotation angle of the upper layer focusing lens to After that, the phase modulation function of the upper layer focusing lens is designed using formula (3) : (8) Step c, determine the combined phase modulation effect of the rotated middle layer synthetic lens and the upper layer focusing lens using formula (8) : (9).

[0011] Further, the coverage range of the acoustic vortex signal is: a truncated cone with one vertex pointing to the planar fan transducer array, the radius of the small circular face of the truncated cone is R1, and the radius of the large circular face is R2.

[0012] Compared with the prior art, the beneficial effects of the present application are: 1. The present application realizes flexible adjustment of the focal point in the axial, radial and angular directions through the relative rotation between multiple layers of discrete acoustic lenses. Only mechanical adjustment of the angle between different lenses is needed to realize arbitrary positioning of the focal point in a limited three-dimensional space without the need to replace the lenses or adjust the structure of the emission array, significantly improving the flexibility of focal point control and system response speed.

[0013] 2. The present application realizes real-time switching of the topological charge of acoustic vortex signals by combining the real-time adjustable phase characteristics of the planar fan transducer array. This design can change the topological charge value of the acoustic vortex simultaneously during the movement of the focal point, realizing the output of controllable topological charge sequence focusing acoustic vortex signals, and providing a more flexible technical means for acoustic vortex communication and multi-particle manipulation.

[0014] 3. The application only uses a limited number of passive lenses and a simplified planar fan-shaped transducer array to achieve complex sound field regulation. Compared with traditional multi-array systems, the application significantly reduces hardware complexity and manufacturing cost, has a more compact structure, and is easy to adjust. It has excellent scalability and potential for practical engineering applications.

[0015] 4. The application can achieve higher signal transmission efficiency and longer transmission distance, solving the problem of serious signal attenuation in the prior art, thereby improving the reliability and stability of underwater acoustic communication. This provides important technical support for the development of future underwater detection, monitoring and communication systems. BRIEF DESCRIPTION OF DRAWINGS

[0016] Figure 1 A three-dimensional omnidirectional emission device for acoustic vortex signals of the application, wherein: 1 is an acoustic phased array circuit, 2 is a planar fan-shaped transducer array, 3 is a lower gradient lens, 4 is a middle synthetic lens, and 5 is an upper focusing lens.

[0017] Figure 2 A radial position regulation diagram for acoustic vortex signals of the application. Wherein, Figure 2 (a) in FIG. 1, from left to right, are the focal plane sound pressure distributions of acoustic vortex signals at radial positions 1, 2, 3 and 4, Figure 2 (b) in FIG. 1, from left to right, are the focal plane phase distributions of acoustic vortex signals at radial positions 1, 2, 3 and 4.

[0018] Figure 3 An axial position regulation diagram for acoustic vortex signals of the application. Wherein, Figure 3 (a) in FIG. 2, from left to right, are the axial cross-sectional sound pressure distributions of acoustic vortex signals at focal point positions 1, 2 and 3, Figure 3 (b) in FIG. 2, from left to right, are the focal plane sound pressure distributions of acoustic vortex signals at axial focal point positions 1, 2 and 3, Figure 3 (c) in FIG. 2, from left to right, are the focal plane phase distributions of acoustic vortex signals at axial focal point positions 1, 2 and 3.

[0019] Figure 4 An angular position regulation diagram for acoustic vortex signals of the application. Wherein, Figure 4 (a) in FIG. 3, from left to right, are the focal plane sound pressure distributions of acoustic vortex signals at angular positions 1, 2, 3 and 4, Figure 4 (b) in FIG. 3, from left to right, are the focal plane phase distributions of acoustic vortex signals at angular positions 1, 2, 3 and 4. DETAILED DESCRIPTION

[0020] In the embodiment, a three-dimensional omnidirectional emission device of acoustic vortex signals is provided, as shown in the figure Figure 1 The whole emission system comprises an acoustic phased array circuit, a planar fan-shaped transducer array, a lower layer gradient lens, a middle layer synthetic lens and an upper layer focusing lens. The acoustic phased array circuit generates N=16 programmable delay square wave signals at a fixed operating frequency; after the N square wave signals are filtered by a low-pass filter to remove high-frequency components, N smooth waveform signals are output; after the N waveform signals are amplified by a wideband power amplifier, N sinusoidal signals with adjustable amplitude and phase are output.

[0021] The number of fan-shaped transducers is M , and the fan angle of each fan-shaped transducer is . According to the phase encoding principle, in order to generate an acoustic vortex signal with a topological charge of l , the initial phase of the sinusoidal signal exciting the m th fan-shaped transducer is . The planar fan-shaped transducer array synthesizes the received N sinusoidal signals in the propagation direction along the propagation axis, and radiates the target acoustic vortex signal with adjustable topological charge order.

[0022] The lower layer gradient lens is nested in the exit surface of the planar fan-shaped transducer array, and there is no gap between the lower layer gradient lens and the planar fan-shaped transducer array. The lower layer gradient lens outputs the modulated target acoustic vortex signal after phase deflection modulation of the target acoustic vortex signal, and deflects the modulated target acoustic vortex signal to one side of the propagation axis for propagation, thereby controlling the propagation direction of the target acoustic vortex signal; the diameters of the lower layer gradient lens and the planar fan-shaped transducer array are both set as a. In the embodiment, according to the linear relationship between the bottom angle α of the lower layer gradient lens and the refraction angle β , the range of the bottom angle α of the lower layer gradient lens is determined as π / 8-π / 6. β

[0023] In specific implementation, according to the generalized Snell's law, the phase modulation function of the lower layer gradient lens is designed by formula (1) , so as to be used for phase deflection modulation of the target acoustic vortex signal. (1) In formula (1), b is the gradient phase change rate of the lower layer gradient lens, and b ∈[25π, 100π]; is the distance between any point on the lower layer gradient lens and the center of the lower layer gradient lens, is the azimuth angle of any point on the lower layer gradient lens, ​Let be the polar coordinates of any point on the surface of the lower gradient lens. For locations with a large thickness in the lower gradient lens, a phase compression method is used to compress the lower gradient lens, designing it as a thin lens. This reduces the attenuation of the target acoustic vortex signal propagating within the lower gradient lens. Simultaneously, a base thickness d is added to the lower gradient lens. min =1mm, to avoid the formation of standing waves.

[0024] A middle-layer synthesizing lens is placed at a distance *d* from the lower-layer gradient lens, perpendicular to the exit surface of the planar sector transducer array. Due to the divergence effect of spherical waves, an excessively large spacing will affect the beam quality of the acoustic vortex signal, while an excessively small spacing will increase the reflection and refraction effects between the lower-layer gradient lens and the middle-layer synthesizing lens. Therefore, *d* is set to 1 mm. The target acoustic vortex signal propagating on one side of the propagation axis undergoes phase modulation in the middle-layer synthesizing lens before being deflected along another angle. β’ It propagates in a direction away from the propagation axis.

[0025] In this embodiment, the phase modulation function of the intermediate layer synthetic lens is designed using equation (2). And used to phase modulate the target acoustic vortex signal; (2) In equation (2), Represents the imaginary unit. This indicates a rounding operation to the nearest integer. k For wave number, F 0 is the preset focal length of the intermediate layer synthetic lens, and F 0∈[100, 200]. The design and fabrication of the intermediate layer synthesizing lens also requires utilizing the principle of phase compression to reduce its thickness, making it a thinner lens and minimizing sound wave attenuation during propagation. Simultaneously, a basic thickness d is added to the intermediate layer synthesizing lens. min =1mm.

[0026] An upper focusing lens is placed in a direction perpendicular to the surface of the middle layer synthesizing lens and at a distance d from the middle layer synthesizing lens. The target acoustic vortex signal, which propagates away from the propagation axis, is phase-modulated in the upper focusing lens and then focused at a fixed focal position to output the final target acoustic vortex signal.

[0027] In practical implementation, the phase modulation function of the upper focusing lens is designed using equation (3). And used to phase modulate the target acoustic vortex signal; (3) The design and fabrication of the upper focusing lens also utilizes the principle of phase compression to reduce its thickness, making it a thinner lens and minimizing sound wave attenuation during propagation. Simultaneously, a base thickness d is added to the upper focusing lens. min =1mm.

[0028] The rotation angles of the lower gradient lens and the middle composite lens are both set to the range of [-π, π]. By adjusting the rotation angles of the lower gradient lens and the middle composite lens, the phase modulation effect between them is changed, thereby altering the refraction angle of the lower gradient lens. β and the deflection angle of the middle layer composite lens β’ This allows for the control of the propagation direction of the final target acoustic vortex signal; In practice, the joint phase modulation function of the lower gradient lens and the middle composite lens is designed according to the following steps. This is to alter the phase modulation effect between the lower gradient lens and the middle synthetic lens. Step a: Adjust the rotation angle of the lower gradient lens to... Then, the phase modulation function of the lower gradient lens is designed using equation (4). : (4) Step b: Adjust the rotation angle of the middle layer synthesizing lens to... Then, the phase modulation function of the intermediate layer synthesizing lens is designed using equation (2). : (5) Step c: Use equation (5) to determine the combined phase modulation effect of the rotated lower gradient lens and middle composite lens. : (6).

[0029] In equation (6), the combined modulation effect obtained after rotating the lower gradient lens and the middle composite lens is equivalent to a gradient phase magnitude equal to Gradient lens, gradient magnitude and rotation angle There exists a cosine function relationship between them.

[0030] The range is [0, 2]. b ],Change The distance between the acoustic vortex signal and the center of the observation surface can be adjusted, such as... Figure 2 As shown.

[0031] The rotation angles of the middle layer synthesizing lens and the upper layer focusing lens are both set to the range of [-π, π]. By adjusting the rotation angles of the middle layer synthesizing lens and the upper layer focusing lens, the phase modulation effect between the middle layer synthesizing lens and the upper layer focusing lens is changed, thereby controlling the focusing direction of the target acoustic vortex signal and changing the final focal point position of the target acoustic vortex signal.

[0032] In practice, the joint phase modulation function of the middle synthesizing lens and the upper focusing lens is designed according to the following steps. This is to alter the phase modulation effect between the middle synthesizing lens and the upper focusing lens. Step a: Adjust the rotation angle of the middle gradient lens to... Then, the phase modulation function of the intermediate layer synthesizing lens is designed using equation (2). : (7) Step b: Adjust the rotation angle of the upper focusing lens to... Then, the phase modulation function of the upper focusing lens is designed using equation (3). : (8) Step c: Use equation (8) to determine the combined phase modulation effect of the rotated middle synthesizing lens and the upper focusing lens. : (9).

[0033] In equation (9), the combined modulation effect obtained by rotating the middle layer synthesizing lens and the upper layer focusing lens is equivalent to a focal length equal to The focusing lens, focal length and rotation angle There exists an inverse proportional function relationship between them. (Change) The axial focal position of the acoustic vortex signal can be adjusted, such as... Figure 3 As shown.

[0034] After adjusting the axial focal position and radial position of the acoustic vortex signal, the angular position of the acoustic vortex signal can be further adjusted by rotating the entire cascaded acoustic lens system by any combined angle, such as... Figure 4 As shown.

[0035] In this embodiment, the coverage area of ​​the acoustic vortex signal is: a truncated cone with its vertex facing the planar sector transducer array, the radius of the small circular surface of the truncated cone is R1, and the radius of the large circular surface is R2, at any position within it.

[0036] In summary, the three-dimensional omnidirectional acoustic vortex signal transmitting device of this invention combines active phase control with passive phase modulation, integrating a special phase distribution into three cascaded acoustic lenses. By adjusting the relative rotation angle between the middle synthesizing lens and the lower gradient lens, the radial position of the focal point can be adjusted on any focal plane. Similarly, by adjusting the relative rotation angle between the upper focusing lens and the middle synthesizing lens, the position of the focal point (vortex center) along the propagation axis can be controlled. Furthermore, by rotating the entire cascaded acoustic lens system by any combined angle, the focal point can be freely adjusted to any position within a finite three-dimensional space. In addition, combined with a simplified planar fan-shaped transducer array, not only can the focal point position be changed in real time, but the topological charge of the emitted focused vortex sound beam can also be freely switched. The method of this invention avoids the need to manufacture a large number of emission sources or multiple sets of different lenses, exhibiting lower cost and higher flexibility, and has broad application potential in underwater acoustic vortex communication and particle manipulation.

Claims

1. A three-dimensional omnidirectional transmitting device for acoustic vortex signals, characterized in that, include: Acoustic phased array circuit, planar sector transducer array, lower gradient lens, middle synthesis lens and upper focusing lens; The acoustic phased array circuit generates N programmable delayed square wave signals at a fixed operating frequency; after the N square wave signals are filtered out by a low-pass filter to remove high-frequency components, N smooth waveform signals are output. After the N waveform signals are amplified by a broadband power amplifier, the output consists of N sine signals with adjustable amplitude and phase. The planar sector transducer array synthesizes the received N sinusoidal signals along the propagation direction of the propagation axis and radiates a target acoustic vortex signal with an adjustable topological charge order. The lower gradient lens is nested on the exit surface of the planar fan-shaped transducer array. After deflecting and modulating the target acoustic vortex signal, it outputs the modulated target acoustic vortex signal, and then refracts it at an angle. β The modulated target acoustic vortex signal is deflected to one side of the propagation axis for propagation, thereby controlling the propagation direction of the target acoustic vortex signal; The intermediate synthesizing lens is placed at a position perpendicular to the exit surface of the planar fan-shaped transducer array and at a distance d from the lower gradient lens; the target acoustic vortex signal propagating on one side of the propagation axis is phase-modulated in the intermediate synthesizing lens and then deflected along another angle. β’ Propagate in a direction away from the propagation axis; The upper focusing lens is placed in a direction perpendicular to the surface of the middle layer synthesizing lens, at a distance d from the middle layer synthesizing lens; After the target acoustic vortex signal propagating away from the propagation axis is phase-modulated in the upper focusing lens, it is focused at a fixed focal position to output the final target acoustic vortex signal. The rotation angles of the lower gradient lens and the middle composite lens are both set to the range of [-π, π]. By adjusting the rotation angles of the lower gradient lens and the middle composite lens, the phase modulation effect between them is changed, thereby altering the refraction angle of the lower gradient lens. β and the deflection angle of the middle layer composite lens β’ This allows for the control of the propagation direction of the final target acoustic vortex signal; The rotation angles of the middle layer synthesizing lens and the upper layer focusing lens are both set to the range of [-π, π]. By adjusting the rotation angles of the middle layer synthesizing lens and the upper layer focusing lens, the phase modulation effect between the middle layer synthesizing lens and the upper layer focusing lens is changed, thereby controlling the focusing direction of the target acoustic vortex signal and changing the final focal point position of the target acoustic vortex signal.

2. The three-dimensional omnidirectional transmitting device for acoustic vortex signals according to claim 1, characterized in that: Based on the base angle α of the lower gradient lens and the refraction angle β The linear relationship between them determines that the range of the bottom angle α of the lower gradient lens is π / 8-π / 6.

3. The three-dimensional omnidirectional transmitting device for acoustic vortex signals according to claim 1, characterized in that: Based on the generalized Snell's law of refraction, the phase modulation function of the lower gradient lens is designed using equation (1). This is used to deflect the phase of the target acoustic vortex signal; (1) In equation (1), b The gradient phase change rate of the lower gradient lens, and b ∈[25π, 100π]; Let be the distance between any point on the lower gradient lens and the center of the lower gradient lens. Let be the azimuth angle of any point above the lower gradient lens. Let be the polar coordinates of any point on the surface of the lower gradient lens.

4. The three-dimensional omnidirectional transmitting device for acoustic vortex signals according to claim 3, characterized in that: The phase modulation function of the intermediate layer synthesis lens is designed using equation (2). And used to phase modulate the target acoustic vortex signal; (2) In equation (2), Represents the imaginary unit. This indicates a rounding operation to the nearest integer. k For wave number, F 0 is the preset focal length of the intermediate layer synthetic lens, and F 0∈[100, 200].

5. A three-dimensional omnidirectional transmitting device for acoustic vortex signals according to claim 4, characterized in that: The phase modulation function of the upper focusing lens is designed using equation (3). And used to phase modulate the target acoustic vortex signal; (3)。 6. A three-dimensional omnidirectional transmitting device for acoustic vortex signals according to claim 4, characterized in that, The joint phase modulation function of the lower gradient lens and the middle composite lens is designed according to the following steps. This is to alter the phase modulation effect between the lower gradient lens and the middle synthetic lens. Step a: Adjust the rotation angle of the lower gradient lens to... Then, the phase modulation function of the lower gradient lens is designed using equation (4). : (4) Step b: Adjust the rotation angle of the middle layer synthesizing lens to... Then, the phase modulation function of the intermediate layer synthesizing lens is designed using equation (2). : (5) Step c: Use equation (5) to determine the combined phase modulation effect of the rotated lower gradient lens and middle composite lens. : (6)。 7. A three-dimensional omnidirectional transmitting device for acoustic vortex signals according to claim 5, characterized in that, The joint phase modulation function of the middle synthesizing lens and the upper focusing lens is designed according to the following steps. This is to alter the phase modulation effect between the middle synthesizing lens and the upper focusing lens. Step a: Adjust the rotation angle of the middle gradient lens to... Then, the phase modulation function of the intermediate layer synthesizing lens is designed using equation (2). : (7) Step b: Adjust the rotation angle of the upper focusing lens to... Then, the phase modulation function of the upper focusing lens is designed using equation (3). : (8) Step c: Use equation (8) to determine the combined phase modulation effect of the rotated middle synthesizing lens and the upper focusing lens. : (9)。 8. The design method for three-dimensional omnidirectional emission of acoustic vortex signals according to claim 1, characterized in that: The coverage area of ​​the acoustic vortex signal is: any position within a truncated cone whose apex faces the planar fan-shaped transducer array, where the radius of the small circular surface of the truncated cone is R1 and the radius of the large circular surface is R2.

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