Vortex transmitting device for quickly constructing focused vortex acoustic beam

Abstract

The invention discloses a vortex transmitting device for quickly constructing a focused vortex acoustic beam, which comprises an excitation signal circuit, a circular transducer, a lower discrete acoustic lens and an upper discrete acoustic lens, through the design of the lenses, any order vortex acoustic beam with topological charge of-3 to + 3 can be expected to be generated in an underwater acoustic communication system; the flexibility and adaptability of communication are improved. The invention provides an innovative solution for the development of an underwater acoustic communication technology, has important technical significance and application potential, not only obviously enhances the stability and anti-interference capability of the signal, but also ensures that the signal keeps high integrity during long-distance transmission in a complex underwater environment.

Description

Technical Field

[0001] The invention relates to a vortex launch device for quickly constructing a focused vortex acoustic beam, and belongs to the technical field of underwater data transmission and acoustic vortex communication applications. Background Art

[0002] There are significant differences in the wavefront structure between traditional plane waves and vortex beams. Vortex beams have a spiral phase wavefront with a phase singularity at the center of the vortex and zero field intensity. The phase distribution of this beam can be described by the mathematical expression exp(ilφ), where l represents the topological charge and φ is the azimuth angle. The spiral phase plate (SPP) is a direct and efficient device for converting plane waves into vortex beams. By designing a suitable spiral phase structure, the SPP can introduce the required phase change to the beam, thereby generating a vortex beam of a specific mode. However, each SPP can only generate a vortex beam of one mode, and has strict requirements on processing accuracy, which limits its flexibility and practicality in multi-mode applications. In contrast, reconfigurable diffractive optical elements, such as spatial light modulators and digital micromirrors, provide a more flexible and fast solution for generating vortex beams. These elements can generate vortex beams of different modes by dynamically adjusting the phase and amplitude of the beam, with higher flexibility and adjustability. However, these methods also face the challenges of large device size and difficulty in integration, which limits their widespread promotion in practical applications. Metamaterials and metasurface technologies provide new solutions for the generation of vortex beams. Metamaterials and metasurfaces have extremely high design freedom and excellent optical properties, and can regulate the phase, amplitude, and polarization state of light on a subwavelength scale. Using these properties, researchers can design small, easy-to-integrate devices for efficient generation and manipulation of vortex beams. The application of these new technologies is expected to overcome the limitations of traditional methods and become one of the alternative solutions for generating vortex beams in the future.

[0003] Since sound waves and light waves have similar characteristics in wave transmission, vortex acoustic beams also entered the field of vision of researchers shortly after the vortex beam was proposed. Vortex acoustic beams have a spiral phase wavefront similar to that of vortex beams, can carry orbital angular momentum, and exhibit unique acoustic properties. At present, the generation technology of vortex acoustic beams is mainly divided into two categories: active and passive. Initial studies generated vortex acoustic beams by designing transducers with spiral structures, but this scheme can only generate vortex acoustic beams with a single topological charge at a fixed frequency, and the adjustment ability is limited. To solve this problem, researchers proposed using an array composed of multiple transducers to control the phase difference between adjacent transducers to 2πl / N (N is the number of transducers) to form a vortex acoustic beam with a topological charge of l. With the development of materials and technologies, researchers have proved that incident acoustic beams without orbital angular momentum can be converted into vortex acoustic beams through metasurfaces, spiral diffraction gratings or acoustic lenses. For example, a study proposed a high-refractive-index metasurface for underwater broadband ultrasonic three-dimensional wavefront shaping. When a plane wave passes through the metasurface, its wavefront becomes spiral. Another study constructed an acoustic resonance layer composed of multiple fan-shaped resonators. By adjusting the ratio of the pipe to the cavity height to obtain the same transmission efficiency, the incident plane wave is converted into a vortex acoustic beam after passing through the acoustic resonance layer.

[0004] Considering that orbital angular momentum can effectively improve communication capacity, vortex acoustic beams also have application potential in underwater high-speed communications. Vortex acoustic beams can not only carry more information, but also maintain good stability and anti-interference capabilities in complex underwater environments. In the future, with the continuous advancement of technology, vortex acoustic beams are expected to play an important role in underwater communications, acoustic imaging, and acoustic manipulation. By analyzing the current vortex acoustic beam construction scheme, it is not difficult to find that the use of passive methods to construct vortex acoustic beams often faces a single acoustic phase modulation structure, the topological charge of the constructed vortex acoustic beam is fixed, and the overall system has poor adjustability. The active method often requires a large number of transmitting sources combined with a complex phased array circuit, and each transmitting source needs to be accurately calibrated in amplitude and phase to construct a high-quality vortex acoustic beam. When the number of sound sources is insufficient, the phase continuity of the vortex acoustic beam will be affected, resulting in a discrete sound pressure distribution in the vortex acoustic beam. Summary of the invention

[0005] The present invention aims to solve the deficiencies of the above-mentioned prior art and proposes a vortex emission device for quickly constructing a focused vortex acoustic beam, so as to efficiently generate and manipulate the vortex acoustic beam to improve the flexibility and adaptability of communication.

[0006] In order to achieve the above-mentioned purpose, the present invention adopts the following technical scheme:

[0007] The invention discloses a vortex emission device for rapidly constructing a focused vortex acoustic beam, which comprises: an excitation signal circuit, a circular transducer, a lower discrete acoustic lens and an upper discrete acoustic lens;

[0008] The excitation signal circuit is connected to an external input power supply, and generates a single programmable delayed square wave signal at a fixed frequency, which is then processed by a low-pass filter and a broadband power amplifier in sequence, thereby outputting a single-channel sinusoidal signal with controllable initial amplitude and phase to the circular transducer;

[0009] The circular transducer array is connected to the excitation signal circuit and generates a plane wave target sound beam along the propagation axis according to the received sinusoidal signal;

[0010] The lower discrete acoustic lens is embedded in the surface of the circular sector transducer, and the radii of the lower discrete acoustic lens and the circular transducer are both set to be a;

[0011] The plane wave target acoustic beam is subjected to spiral square phase modulation in the lower discrete acoustic lens, and then outputs a modulated quasi-vortex target acoustic beam, and continues to propagate on the propagation axis;

[0012] The upper discrete acoustic lens is placed at a distance d from the lower discrete acoustic lens in a direction perpendicular to the surface of the circular transducer array, the lower discrete acoustic lens is fixed, and the rotation angle of the upper discrete acoustic lens is [-π / 2, π / 2];

[0013] The quasi-vortex target acoustic beam is modulated with a square spiral phase and a focusing phase in the upper discrete acoustic lens, deflected to the propagation axis at different refraction angles for propagation, and focused at a focal position on the propagation axis to finally output a focused vortex acoustic beam;

[0014] By adjusting the rotation angle of the upper discrete acoustic lens to change the phase modulation effect between the upper discrete acoustic lens and the lower discrete acoustic lens, the topological charge of the focused vortex acoustic beam can be flexibly controlled to achieve vortex emission of the focused vortex acoustic beam.

[0015] The vortex launch device for rapidly constructing a focused vortex acoustic beam according to the present invention is also characterized in that, according to the range of the topological charge of the focused vortex acoustic beam to be used, the phase modulation function of the lower discrete acoustic lens is designed using formula (1): , which is used to perform spiral square phase modulation on the plane wave target acoustic beam:

[0016] (1)

[0017] In formula (1), b is a constant. There is a linear relationship between the range of the topological charge of the focused vortex acoustic beam that can be constructed and b. The value of b can be determined according to the actual use range of the topological charge of the focused vortex acoustic beam. is the distance between any point on the lower discrete acoustic lens and the center of the lens, is the azimuth angle of any point on the lower discrete acoustic lens, is the polar coordinate of any point on the surface of the underlying discrete acoustic lens.

[0018] Further, according to the generalized Fresnel law, the phase modulation function of the upper discrete acoustic lens is designed using equation (2): , and is used to align the vortex target acoustic beam for spiral square phase and focusing phase modulation:

[0019] (2)

[0020] In formula (2), is the focusing phase integrated on the upper discrete acoustic lens, and , k is the wave number, and F is the distance between the focus on the propagation axis and the center of the upper discrete acoustic lens.

[0021] Furthermore, the joint phase modulation function of the lower discrete acoustic lens and the upper discrete acoustic lens is designed according to the following steps: , to change the phase modulation effect between the upper discrete acoustic lens and the upper discrete acoustic lens:

[0022] Step a, fixing the lower discrete acoustic lens;

[0023] Step b: After adjusting the rotation angle of the upper discrete acoustic lens to θ, the phase modulation function of the upper discrete acoustic lens is designed using formula (3): :

[0024] (3)

[0025] Step c: Determine the joint phase modulation effect between the fixed lower discrete acoustic lens and the rotated upper discrete acoustic lens using equation (4) :

[0026] (4).

[0027] Furthermore, the topological charge of the focused vortex acoustic beam ranges from all integers within a range of -3 to +3.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. The present invention overcomes the limitations of conventional technology in generating vortex acoustic beams with a topological charge of -3 to +3 by combining two discrete acoustic lenses with a special phase modulation effect and rotating them at any angle. The method of the present invention not only exhibits excellent flexibility and adjustability, but also can control the characteristics of the vortex acoustic beam with high precision, thereby achieving higher-resolution imaging and positioning in fields such as ocean exploration and underwater navigation. This high-precision phase modulation method makes it possible for the miniaturization and multifunctionality of future acoustic equipment.

[0030] 2. The present invention applies discrete acoustic lens combinations to underwater acoustic vortex communication systems, effectively solving the signal attenuation and interference problems of traditional systems in complex environments. The generated vortex acoustic beam exhibits good stability and anti-interference capabilities, and can maintain high signal integrity during long-distance transmission. This advantage is particularly important in long-distance transmission scenarios such as deep-sea exploration and submarine communications, helping to reduce signal loss and bit error rate, and achieving more reliable communication.

[0031] 3. The present invention simplifies the system design and improves the processing efficiency of the overall system. The discrete acoustic lens design significantly reduces manufacturing and maintenance costs while improving signal processing efficiency by avoiding the complexity of traditional phased array circuits. Unlike traditional phased array systems that require a large number of independent control units, the present invention achieves the same or better effects through simple rotation adjustments, greatly reducing system size and power consumption. This innovation not only enhances the generation and control capabilities of vortex acoustic beams, but also lays a solid foundation for the stable and efficient development of underwater acoustic vortex communication systems, and provides valuable reference for research in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The present invention is a schematic diagram of a complete transmitting system of a vortex transmitting device for rapidly constructing a focused vortex acoustic beam; wherein: 1─excitation signal circuit, 2─flat circular transducer, 3─lower discrete acoustic lens, 4─upper discrete acoustic lens.

[0033] Figure 2 It is the sound field distribution diagram of the integer-order vortex sound beam generated at different angles of the rotating upper discrete sound lens in the present invention; wherein, Figure 2 (a) shows the sound pressure distribution of the focused vortex sound beam with topological charge equal to -1, 0 and 1 from left to right. Figure 2 (b) in the figure shows the phase distribution of the focused vortex acoustic beam with topological charge equal to -1, 0 and 1 from left to right.

[0034] Figure 3 The acoustic field distribution diagram of the fractional-order vortex acoustic beam generated at different angles of the rotating upper discrete acoustic lens in the present invention; Figure 3(a) shows the sound pressure distribution of the focused vortex sound beam with topological charge equal to 0.2, 0.4, 0.6 and 0.8 from left to right. Figure 3 (b) shows the phase distribution of the focused vortex acoustic beam with topological charge equal to 0.2, 0.4, 0.6 and 0.8 from left to right. DETAILED DESCRIPTION

[0035] In this embodiment, a vortex launch device for quickly constructing a focused vortex acoustic beam is provided. Figure 1 As shown, the whole transmitting system includes: an excitation signal circuit, a circular transducer, a lower discrete acoustic lens and an upper discrete acoustic lens;

[0036] The excitation signal circuit is connected to an external input power supply, and a single programmable delayed square wave signal is generated at a fixed frequency, which is then processed by a low-pass filter and a broadband power amplifier in sequence, thereby outputting a single-channel sinusoidal signal with controllable initial amplitude and phase to the circular transducer;

[0037] The circular transducer is connected to the excitation signal circuit and generates a plane wave target sound beam along the propagation axis according to the received sinusoidal signal;

[0038] The lower discrete acoustic lens is nested on the surface of the circular sector transducer. There should be no gap between the lower discrete acoustic lens and the circular transducer. The radius of the lower discrete acoustic lens and the circular transducer are both set to a. To ensure that the plane wave target sound beam emitted by the circular transducer has strong directivity, the value of a should not be less than 25 mm.

[0039] After the plane wave target acoustic beam is subjected to spiral square phase modulation in the lower discrete acoustic lens, the modulated quasi-vortex target acoustic beam is output and continues to propagate on the propagation axis;

[0040] The upper discrete acoustic lens is placed perpendicular to the circular transducer array surface and at a distance d from the lower discrete acoustic lens. The initial value of d is set to 1mm. The distance d is not fixed. Changing the distance d can also adjust the position of the focus. The interval should not be set too large, because the spherical wave will have a divergence effect, which will affect the quality of the vortex target sound beam, make the lower discrete acoustic lens fixed, and make the rotation angle of the upper discrete acoustic lens [-π / 2,π / 2];

[0041] The quasi-vortex target acoustic beam is modulated with square spiral phase and focusing phase in the upper discrete acoustic lens, and then deflected to the propagation axis at different refraction angles for propagation, and then all focused at the focal position on the propagation axis. Finally, a focused vortex acoustic beam is output;

[0042] By adjusting the rotation angle of the upper discrete acoustic lens to change the phase modulation effect between the upper discrete acoustic lens and the lower discrete acoustic lens, the topological charge of the focused vortex acoustic beam can be flexibly controlled to realize the rapid construction of a vortex launching device for the focused vortex acoustic beam.

[0043] In this embodiment, according to the size range of the topological charge of the focused vortex acoustic beam to be used, the phase modulation function of the lower discrete acoustic lens is designed using equation (1): , which is used to perform spiral square phase modulation on the plane wave target acoustic beam:

[0044] (1)

[0045] In formula (1), b is a constant. There is a linear relationship between the range of the topological charge of the focused vortex acoustic beam that can be constructed and b. The value of b can be determined according to the actual use range of the topological charge of the focused vortex acoustic beam. In order to avoid excessive angular phase changes, the value of b should not be too large, otherwise the center of the processed lower discrete acoustic lens will be distorted. is the distance between any point on the lower discrete acoustic lens and the center of the lens, is the azimuth angle of any point on the lower discrete acoustic lens, is the polar coordinate of any point on the surface of the lower discrete acoustic lens. For locations where the lower discrete acoustic lens is thick, the phase compression method is used to compress the thickness of the lower discrete acoustic lens, and the lower discrete acoustic lens is designed as a thin lens. This can reduce the attenuation of the plane wave target sound beam when it propagates in the lower discrete acoustic lens. At the same time, a basic thickness d is added to the sawtooth lens. min =1mm, to avoid the formation of standing waves.

[0046] In this embodiment, according to the generalized Fresnel law, the phase modulation function of the upper discrete acoustic lens is designed using equation (2): , and is used to align the vortex target acoustic beam for spiral square phase and focusing phase modulation:

[0047] (2)

[0048] In formula (2), is the focusing phase integrated on the upper discrete acoustic lens, which can be expressed as , k is the wave number, and F is the distance between the focus on the propagation axis and the center of the upper discrete acoustic lens. The focusing phase must be integrated on the upper discrete acoustic lens. If it is integrated on the lower discrete acoustic lens, the quality of the focused vortex acoustic beam will deteriorate. In the design and processing of the upper discrete acoustic lens, it is also necessary to use the principle of phase compression to compress the thickness of the upper discrete acoustic lens to make it a thin lens, so as to reduce the attenuation of the quasi-vortex target acoustic beam when propagating in the upper discrete acoustic lens.

[0049] In this embodiment, the joint phase modulation function of the lower discrete acoustic lens and the upper discrete acoustic lens can be designed according to the following steps: , to change the phase modulation effect between the upper discrete acoustic lens and the upper discrete acoustic lens:

[0050] Step a: fix the lower discrete acoustic lens so that the phase modulation function of the lower discrete acoustic lens remains as follows: .

[0051] Step b: After adjusting the rotation angle of the upper discrete acoustic lens to θ, the phase modulation function of the upper discrete acoustic lens is designed using equation (3): :

[0052] (3)

[0053] Step c: Determine the joint phase modulation effect of the fixed lower discrete acoustic lens and the rotated upper discrete acoustic lens using equation (4): :

[0054] (4)

[0055] The first term in equation (4) corresponds to a spiral phase modulation effect with a topological charge of l = 2bθφ0, and the second and third terms correspond to a spiral phase modulation effect with a topological charge of The fixed phase shift and a focusing phase effect will not affect the spiral phase modulation effect. Therefore, the joint modulation effect of the lower discrete acoustic lens and the rotated upper discrete acoustic lens is equivalent to a spiral phase plate with a spiral phase size equal to 2bθφ0, and there is a linear relationship between the topological charge size and the rotation angle θ.

[0056] Combined with the rotation angle range of the upper discrete acoustic lens [-π / 2, π / 2], in this embodiment, a vortex launch device for quickly constructing a focused vortex acoustic beam can quickly construct a focused vortex acoustic beam with a topological charge size range of all integers within -3 to +3. The constructed integer-order vortex acoustic beam is as follows: Figure 2 shown.

[0057] According to formula (2), the combination of the lower discrete acoustic lens and the upper discrete acoustic lens can be used to construct not only integer-order vortex sound beams, but also fractional-order vortex sound beams. The constructed fractional-order focused vortex sound beam is as follows: Figure 3 shown.

[0058] In summary, the vortex transmitter of the present invention will significantly enhance the stability and anti-interference ability of the signal, ensuring high signal integrity during long-distance transmission in complex underwater environments. At the same time, the design of the discrete acoustic lens simplifies the system structure and reduces hardware requirements, thereby improving the processing efficiency of the overall system. In general, the present invention provides an innovative solution for the development of underwater communication technology, which has important technical significance and application potential.

Claims

1. A vortex launch device for rapidly constructing a focused vortex acoustic beam, characterized in that: include: An excitation signal circuit, a circular transducer, a lower discrete acoustic lens and an upper discrete acoustic lens; The excitation signal circuit is connected to an external input power supply, and generates a single programmable delayed square wave signal at a fixed frequency, which is then processed by a low-pass filter and a broadband power amplifier in sequence, thereby outputting a single-channel sinusoidal signal with controllable initial amplitude and phase to the circular transducer; The circular transducer array is connected to the excitation signal circuit and generates a plane wave target sound beam along the propagation axis according to the received sinusoidal signal; The lower discrete acoustic lens is embedded in the surface of the circular sector transducer, and the radii of the lower discrete acoustic lens and the circular transducer are both set to be a; The plane wave target acoustic beam is subjected to spiral square phase modulation in the lower discrete acoustic lens, and then outputs a modulated quasi-vortex target acoustic beam, and continues to propagate on the propagation axis; The upper discrete acoustic lens is placed at a distance d from the lower discrete acoustic lens in a direction perpendicular to the surface of the circular transducer array, the lower discrete acoustic lens is fixed, and the rotation angle of the upper discrete acoustic lens is [-π / 2, π / 2]; The quasi-vortex target acoustic beam is modulated with a square spiral phase and a focusing phase in the upper discrete acoustic lens, deflected to the propagation axis at different refraction angles for propagation, and focused at a focal position on the propagation axis to finally output a focused vortex acoustic beam; By adjusting the rotation angle of the upper discrete acoustic lens to change the phase modulation effect between the upper discrete acoustic lens and the lower discrete acoustic lens, the topological charge of the focused vortex acoustic beam can be flexibly controlled to achieve vortex emission of the focused vortex acoustic beam.

2. A vortex emission device for rapidly constructing a focused vortex acoustic beam according to claim 1, characterized in that: According to the range of topological charge of the focused vortex acoustic beam to be used, the phase modulation function of the lower discrete acoustic lens is designed using equation (1): , which is used to perform spiral square phase modulation on the plane wave target acoustic beam: (1) In formula (1), b is a constant. There is a linear relationship between the range of the topological charge of the focused vortex acoustic beam that can be constructed and b. The value of b can be determined according to the actual use range of the topological charge of the focused vortex acoustic beam. is the distance between any point on the lower discrete acoustic lens and the center of the lens, is the azimuth angle of any point on the lower discrete acoustic lens, are the polar coordinates of any point on the surface of the underlying discrete acoustic lens.

3. A vortex emission device for rapidly constructing a focused vortex acoustic beam according to claim 2, characterized in that: According to the generalized Fresnel law, the phase modulation function of the upper discrete acoustic lens is designed using equation (2): , and is used to align the vortex target acoustic beam for spiral square phase and focusing phase modulation: (2) In formula (2), is the focusing phase integrated on the upper discrete acoustic lens, and , k is the wave number, and F is the distance between the focus on the propagation axis and the center of the upper discrete acoustic lens.

4. A vortex emission device for rapidly constructing a focused vortex acoustic beam according to claim 1, characterized in that: The joint phase modulation function of the lower discrete acoustic lens and the upper discrete acoustic lens is designed according to the following steps: , to change the phase modulation effect between the upper discrete acoustic lens and the upper discrete acoustic lens: Step a, fixing the lower discrete acoustic lens; Step b: After adjusting the rotation angle of the upper discrete acoustic lens to θ, the phase modulation function of the upper discrete acoustic lens is designed using formula (3): : (3) Step c: Determine the joint phase modulation effect between the fixed lower discrete acoustic lens and the rotated upper discrete acoustic lens using equation (4) : (4)。 5. A vortex emission device for rapidly constructing a focused vortex acoustic beam according to claim 1, characterized in that: The topological charge of the focused vortex acoustic beam ranges from all integers within a range of -3 to +3.

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