A vortex launch device for rapidly constructing a focused vortex acoustic beam

Abstract

This invention discloses a vortex emission device for rapidly constructing a focused vortex acoustic beam. The device comprises an excitation signal circuit, a circular transducer, a lower discrete acoustic lens, and an upper discrete acoustic lens. This lens design is expected to generate vortex acoustic beams of any order, with a topological charge ranging from -3 to +3, in underwater acoustic communication systems, thereby improving communication flexibility and adaptability. This invention provides an innovative solution for the development of underwater acoustic communication technology and has significant technical significance and application potential. It not only significantly enhances signal stability and anti-interference capabilities, but also ensures high signal integrity during long-distance transmission in complex underwater environments.

Description

Technical Field

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

[0002] Traditional plane waves and vortex beams differ significantly in their wavefront structures. A vortex beam has a spiral phase wavefront with a phase singularity at the vortex center and zero field intensity. The phase distribution of such a beam can be described by the mathematical expression exp(ilφ), where l represents the topological charge and φ is the azimuthal angle. A spiral phase plate (SPP) is a direct and efficient device for converting plane waves into vortex beams. By designing a suitable spiral phase structure, an SPP can introduce a desired phase shift into the beam, thereby generating a vortex beam with a specific mode. However, each SPP can only generate a single vortex beam mode and requires stringent fabrication precision, limiting its flexibility and practicality in multimodal applications. In contrast, reconfigurable diffractive optical elements, such as spatial light modulators and digital micromirrors, offer more flexible and rapid solutions for generating vortex beams. These elements can generate vortex beams of different modes by dynamically adjusting the phase and amplitude of the beam, offering greater flexibility and tunability. However, these approaches also face the challenges of large device size and difficulty in integration, limiting their widespread adoption in practical applications. Metamaterials and metasurfaces offer new solutions for generating vortex beams. They offer exceptional design freedom and superior optical properties, enabling manipulation of the phase, amplitude, and polarization of light on a subwavelength scale. Leveraging these properties, researchers can design compact, easily integrated devices for efficient generation and manipulation of vortex beams. These new technologies are expected to overcome the limitations of traditional methods and become a promising alternative for generating vortex beams in the future.

[0003] Since sound waves and light waves have similar properties in wave propagation, vortex acoustic beams also came into the attention of researchers shortly after the concept of vortex beams 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. Currently, technologies for generating vortex acoustic beams are mainly divided into two categories: active and passive. Initial research used spiral transducers to generate vortex acoustic beams, but this approach can only produce vortex acoustic beams with a single topological charge at a fixed frequency and has limited adjustability. To address this problem, researchers proposed using an array of multiple transducers, controlling 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 demonstrated that an incident acoustic beam without orbital angular momentum can be converted into a vortex acoustic beam using metasurfaces, spiral diffraction gratings, or acoustic lenses. For example, one study proposed a high-refractive-index metasurface for underwater broadband ultrasonic three-dimensional wavefront shaping. When a plane wave passes through this metasurface, its wavefront becomes spiral-shaped. 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 achieve 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 the problem of a single acoustic phase modulation structure, the topological charge of the constructed vortex acoustic beam is fixed, and the overall system has poor adjustability. Active methods often require a large number of transmitting sources combined with a complex phased array circuit. 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 address the deficiencies of the above-mentioned prior art and proposes a vortex emission device for rapidly 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 object, the present invention adopts the following technical solutions:

[0007] The invention provides 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 square wave signal with a programmable delay at a fixed frequency, which is then processed by a low-pass filter and a broadband power amplifier in sequence, thereby outputting a single 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 nested on the surface of the circular sector transducer, and the radius of the lower discrete acoustic lens and the circular transducer are both set to 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, which continues to propagate along the propagation axis;

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

[0013] The quasi-vortex target acoustic beam is modulated with a square spiral phase and a focus 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 lower discrete acoustic lens.

[0018] Furthermore, according to the generalized Fresnel law, the phase modulation function of the upper discrete acoustic lens is designed using formula (2): , and is used to align the vortex target acoustic beam for spiral square phase and focus 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: Use equation (4) to determine the joint phase modulation effect between the fixed lower discrete acoustic lens and the rotated upper discrete acoustic lens. :

[0026] (4).

[0027] Furthermore, the topological charge of the focused vortex acoustic beam ranges from integers between -3 and +3.

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

[0029] 1. This invention overcomes the limitations of conventional techniques in generating vortex beams with topological charges ranging from -3 to +3 by combining two discrete acoustic lenses with a unique phase modulation effect and rotating them at arbitrary angles. This method not only demonstrates remarkable flexibility and adjustability but also enables high-precision control of vortex beam characteristics, enabling higher-resolution imaging and positioning in fields such as ocean exploration and underwater navigation. This high-precision phase modulation method opens the door to the miniaturization and multifunctionality of future acoustic devices.

[0030] 2. This invention applies a combination of discrete acoustic lenses to an underwater acoustic vortex communication system, effectively addressing the signal attenuation and interference issues faced by traditional systems in complex environments. The resulting vortex acoustic beam exhibits excellent stability and anti-interference capabilities, maintaining high signal integrity over 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 rates, achieving more reliable communication.

[0031] 3. This invention simplifies system design and improves overall system processing efficiency. This discrete acoustic lens design significantly reduces manufacturing and maintenance costs by avoiding the complexity of traditional phased array circuits, while also improving signal processing efficiency. Unlike traditional phased array systems that require a large number of independent control units, this invention achieves the same or better results through simple rotational adjustments, significantly 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 a valuable reference for research in related fields. BRIEF DESCRIPTION OF THE DRAWINGS

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

[0033] Figure 2 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) in the figure 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 vortex acoustic beam generated by the rotating upper discrete acoustic lens at different angles in the present invention; Figure 3(a) in the figure 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) in the figure 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 emission device for rapidly constructing a focused vortex acoustic beam is provided. Figure 1 As shown, the entire 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 generates a single square wave signal with programmable delay at a fixed frequency. After being processed by a low-pass filter and a broadband power amplifier, a single sinusoidal signal with controllable initial amplitude and phase is output 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 must 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 must not be less than 25mm.

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

[0040] Place the upper discrete acoustic lens perpendicular to the surface of the circular transducer array 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, and changing the distance d can also adjust the position of the focus. The spacing should not be set too large, because the spherical wave will have a divergent effect, which will affect the quality of the vortex target acoustic beam. The lower discrete acoustic lens is fixed and the rotation angle of the upper discrete acoustic lens is set to [-π / 2,π / 2].

[0041] The quasi-vortex target acoustic beam undergoes square spiral phase and focus phase modulation in the upper discrete acoustic lens, and is deflected to the propagation axis at different refraction angles for propagation, and then all are 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 emission 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 formula (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 formula (2): , and is used to align the vortex target acoustic beam for spiral square phase and focus 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 focal point on the propagation axis and the center of the upper discrete acoustic lens. The focused 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. The principle of phase compression should also be utilized in the design and processing of the upper discrete acoustic lens. The thickness of the upper discrete acoustic lens should be compressed to form a thin lens, thereby reducing the attenuation of the quasi-vortex target acoustic beam as it propagates through 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: The lower discrete acoustic lens is fixed, so the phase modulation function of the lower discrete acoustic lens remains as .

[0051] Step b: After adjusting the rotation angle of the upper discrete acoustic lens to θ, use formula (3) to design the phase modulation function of the upper discrete acoustic lens: :

[0052] (3)

[0053] Step c: Use formula (4) to determine the joint phase modulation effect of the fixed lower discrete acoustic lens and the rotated upper discrete acoustic lens. :

[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 topological charge of The fixed phase shift and a focusing phase effect do not affect the spiral phase modulation effect. Therefore, the combined 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 equal to 2bθφ0. There is a linear relationship between the topological charge 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 rapidly constructing a focused vortex acoustic beam can rapidly construct a focused vortex acoustic beam with a topological charge size ranging from -3 to +3 for all integers. 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 this invention significantly enhances signal stability and anti-interference capabilities, ensuring high signal integrity during long-distance transmission in complex underwater environments. Furthermore, the discrete acoustic lens design simplifies the system architecture and reduces hardware requirements, thereby improving overall system processing efficiency. Overall, this invention provides an innovative solution for the development of underwater communication technology, with significant technical significance and application potential.

Claims

1. A vortex emission 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 square wave signal with a programmable delay at a fixed frequency, which is then processed by a low-pass filter and a broadband power amplifier in sequence, thereby outputting a single 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 nested on the surface of the circular transducer, and the radius of the lower discrete acoustic lens and the circular transducer are both set to 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, which continues to propagate along the propagation axis; The upper discrete acoustic lens is placed in a direction perpendicular to the surface of the circular transducer array and at a distance d from the lower discrete acoustic lens, the lower discrete acoustic lens is fixed, and the rotation angle of the upper discrete acoustic lens is set to [-π / 2, π / 2]; The quasi-vortex target acoustic beam is modulated with a square spiral phase and a focus 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 the topological charge of the focused vortex acoustic beam required 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: (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, is the polar coordinate of any point on the surface of the lower 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 formula (2): , and is used to align the vortex target acoustic beam for spiral square phase and focus 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: Use equation (4) to determine the joint phase modulation effect between the fixed lower discrete acoustic lens and the rotated upper discrete acoustic lens. : (4)。 5. The 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 integers within a range of -3 to +3.

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