Sound track angular momentum multiplexing communication system and communication method based on rotating Doppler

Abstract

The application provides a sound track angular momentum multiplexing communication system based on a rotating Doppler, which comprises a sound track angular momentum transmitting array and a rotating demultiplexer, wherein the sound track angular momentum transmitting array is used for constructing perfect sound vortexes by using sound track angular momentum signals with different topological orders to be combined into one sound track angular momentum multiplexing signal which is simultaneously transmitted on the same channel; the rotating demultiplexer is used for signal separation of the received sound track angular momentum multiplexing signal which is simultaneously transmitted on the same channel based on a rotating Doppler to extract information carried in each order signal; and a central axis of a sound sensor of the rotating demultiplexer coincides with a preset first axis. The sound track angular momentum multiplexing communication system can improve the communication efficiency based on the sound track angular momentum and reduce the complexity of the sound track angular momentum multiplexing communication system.

Description

Technical Field

[0001] This invention belongs to the field of acoustic communication technology, and particularly relates to a communication system and method based on rotating Doppler acoustic orbital angular momentum multiplexing. Background Technology

[0002] Due to limitations in sound speed and frequency, acoustic communication has a lower data rate compared to electromagnetic communication. However, acoustic communication technology has wide applications in underwater communication and communication in electromagnetically sensitive areas. Therefore, it is crucial to maximize the acoustic communication rate within the limited available bandwidth. The spatial field distribution of orbital angular momentum forms a complete orthogonal basis, with different topological orders being independent and orthogonal to each other. Therefore, the transmitted signal can be multiplexed onto orbital angular momentum of different topological orders. By introducing acoustic orbital angular momentum multiplexing technology, the communication rate can be increased several times over compared to existing communication systems.

[0003] However, current acoustic orbital angular momentum demultiplexers are very complex. Scanning type requires point-by-point scanning of the spatial field distribution and two-dimensional inner product calculation, which is very time-consuming and requires processing a large amount of data. Array type requires a large number of sensors and two-dimensional inner product calculation, and the demultiplexing accuracy is related to the number of sensors. A large number of sensors results in a large amount of signal processing data and complex hardware circuitry with high cost. Passive metamaterial type uses metamaterial demultiplexing, but it has insertion loss, cannot demodulate high-order signals, and cannot demodulate acoustic orbital angular momentum of multiple orders simultaneously. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a communication system and method based on rotating Doppler acoustic orbital angular momentum multiplexing, which can improve the communication efficiency based on acoustic orbital angular momentum while reducing the complexity of the communication system.

[0005] To achieve the above objectives, the technical solution of the present invention is as follows: a rotating Doppler-based acoustic orbital angular momentum multiplexing communication system, comprising: an acoustic orbital angular momentum transmitting array and a rotating demultiplexer, wherein the acoustic orbital angular momentum transmitting array is used to construct perfect acoustic vortices from acoustic orbital angular momentum signals with different topological orders to merge them into a single acoustic orbital angular momentum multiplexed signal transmitted simultaneously on the same channel; the rotating demultiplexer is used to perform signal separation on the received acoustic orbital angular momentum multiplexed signal transmitted simultaneously on the same channel based on rotating Doppler to extract information carried in each order signal; wherein the central axis of rotation of the acoustic sensor of the rotating demultiplexer coincides with a preset first axis.

[0006] Preferably, the acoustic orbit angular momentum emission array includes an acoustic field encoding module, a driving module, and a phased array composed of multiple independently controlled acoustic transducer units. The acoustic field encoding module encodes and multiplexes the information to be emitted onto acoustic orbit angular momentum of different orders and outputs multiple driving signals based on a preset program. The driving module drives multiple acoustic transducer units in the phased array to emit acoustic orbit angular momentum multiplexed signals that satisfy perfect acoustic vortexes.

[0007] Preferably, the sound field encoding module is implemented based on an FPGA. The FPGA receives instructions from the host computer and calculates a driving signal including the transmission amplitude and phase based on an iterative optimization algorithm. The objective function of the iterative optimization algorithm is described by mathematical forms in the spatial and frequency domains. The driving module drives each acoustic transducer unit in the phased array to transmit ultrasonic waves according to their respective required amplitude and phase based on the transmission amplitude and phase to construct a perfect vortex sound field carrying multiplexing information. The driving signal satisfies the helical phase modulation required to construct a perfect acoustic vortex.

[0008] Preferably, the driving signal is superimposed with amplitude, phase, or frequency modulation to achieve acoustic track angular momentum multiplexing communication, and is compatible with time division multiplexing, space division multiplexing, and frequency division multiplexing; or, the driving signal is superimposed with a multiple input multiple output system, and when multiple sets of transmitting arrays, multiple sensors, or multiple sets of rotating devices are used, a multiple input multiple output system is constructed to improve the communication effect.

[0009] Preferably, the FPGA controls each acoustic transducer unit in the phased array according to the driving signal calculated by the iterative optimization algorithm, so as to realize the control of whether the acoustic orbital angular momentum is emitted and the radial intensity, as well as the anti-aliasing optimization between topological orders.

[0010] Preferably, the multiple acoustic transducer units in the phased array are arranged in a concentric ring array, a spiral array, or a uniform square array.

[0011] Preferably, the rotating demultiplexer includes a rotating device and an acoustic sensor mounted on the rotating device. The rotating device controls the acoustic sensor to rotate, thereby introducing the rotating Doppler effect to separate the received acoustic orbital angular momentum in the frequency domain. Then, FFT analysis is performed to obtain the amplitude and phase information of the acoustic vortex in the frequency domain.

[0012] Preferably, the acoustic sensor is connected to the rotary motor on the rotating device via a conductive slip ring, which transmits the signal from the acoustic sensor to the signal processing device; or, the acoustic sensor is equipped with a wireless communication device, which transmits the signal from the acoustic sensor to the signal processing device.

[0013] Based on the same concept, this invention also provides a rotating Doppler-based acoustic orbital angular momentum multiplexing communication method, applied to the aforementioned rotating Doppler-based acoustic orbital angular momentum multiplexing communication system, comprising the following steps: controlling the rotation of the acoustic sensor of the rotating demultiplexer to acquire the acoustic orbital angular momentum multiplexing signal that satisfies the perfect acoustic vortex emitted by the acoustic orbital angular momentum emission array to achieve separation of acoustic orbital angular momentum in the frequency domain; wherein, the acoustic orbital angular momentum multiplexing signal is generated by controlling the phased array emission through a preset gradient optimization algorithm or genetic algorithm based on a preset phased array arrangement and emission performance parameters; rotating and receiving the acoustic orbital angular momentum multiplexing signal, performing Fourier transform on the received signal to obtain the amplitude and phase of the acoustic orbital angular momentum, and decoding based on a preset signal modulation method and encoding rules to obtain communication data.

[0014] Preferably, when the axis of rotation of the acoustic sensor is not aligned with the axis of acoustic orbit angular momentum emission, the midpoint of the emitted acoustic orbit angular momentum is dynamically adjusted in the gradient optimization algorithm or genetic optimization algorithm according to the quality of the received signal to track the rotating multiplexer and thus achieve a good alignment effect.

[0015] Because of the above technical solutions, this invention has the following advantages and positive effects compared with the prior art:

[0016] 1. This invention constructs a perfect vortex sound field, concentrating energy on the same radius, which can avoid energy dispersion, improve reception efficiency, and thus improve communication efficiency based on acoustic orbital angular momentum.

[0017] 2. The rotating demultiplexer in this invention receives orbital angular momentum multiplexed signals while continuously rotating around a preset axis. This introduces a rotating Doppler frequency shift, enabling the separation of orbital angular momentum signals of different topological orders within the composite signal, thereby extracting the information carried by each order signal. This achieves both improved communication efficiency based on acoustic orbital angular momentum and reduced complexity of the acoustic orbital angular momentum multiplexing communication system.

[0018] 3. Based on the construction of a perfect vortex sound field by the acoustic orbit angular momentum emission array and the introduction of rotating Doppler frequency shift by the rotating demultiplexer, this invention can superimpose amplitude, phase or frequency modulation to realize acoustic orbit angular momentum multiplexing communication and is compatible with other multiplexing technologies, such as time division multiplexing, space division multiplexing and frequency division multiplexing. It also improves the system compatibility while simplifying the hardware complexity.

[0019] 4. The FPGA described in this invention can control each acoustic transducer unit in the phased array based on the driving signal generated by the built-in program, thereby realizing the control of whether the acoustic orbital angular momentum is emitted and the radial intensity, as well as the anti-aliasing optimization between topological orders. Attached Figure Description

[0020] The specific embodiments of the present invention will be further described in detail below with reference to the accompanying drawings, wherein:

[0021] Figure 1 This is a diagram of the acoustic orbital angular momentum multiplexing communication system based on rotating Doppler according to the present invention.

[0022] Figure 2 The diagram shows the acoustic field and energy radius distribution of the multiplexed signal emitted by the acoustic orbital angular momentum emission array of this invention. Detailed Implementation

[0023] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of the present invention will become clearer from the following description and claims. It should be noted that the drawings are all in a very simplified form and use non-precise ratios, and are only used to facilitate and clarify the illustration of the embodiments of the present invention.

[0024] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0025] First Embodiment

[0026] This embodiment provides a rotating Doppler-based acoustic orbital angular momentum multiplexing communication system, including: an acoustic orbital angular momentum transmitting array and a rotating demultiplexer. The acoustic orbital angular momentum transmitting array is used to construct perfect acoustic vortices from acoustic orbital angular momentum signals with different topological orders to merge them into a single acoustic orbital angular momentum multiplexed signal transmitted simultaneously on the same channel. The rotating demultiplexer is used to perform signal separation on the received acoustic orbital angular momentum multiplexed signal transmitted simultaneously on the same channel based on rotating Doppler to extract the information carried in each order signal. The central axis of rotation of the acoustic sensor of the rotating demultiplexer coincides with a preset first axis.

[0027] This embodiment constructs a perfect vortex sound field, concentrating energy at the same radius, thus avoiding energy dispersion and improving reception efficiency. Simultaneously, the rotating demultiplexer in this embodiment receives the orbital angular momentum multiplexed signal while continuously rotating around a preset axis. This introduces a rotating Doppler frequency shift, enabling the separation of orbital angular momentum signals of different topological orders within the composite signal, thereby extracting the information carried by each order of signal.

[0028] The communication system in this embodiment can overcome the shortcomings of optical communication and electromagnetic communication in specific scenarios, such as underwater communication and communication in electromagnetically sensitive areas. It has the advantages of high communication efficiency and low system complexity.

[0029] See details Figure 1 The acoustic orbit angular momentum emission array includes an acoustic field encoding module, a driving module, and multiple acoustic transducers.

[0030] Specifically, the acoustic field encoding module encodes and multiplexes the information to be transmitted onto acoustic orbital angular momentum of different orders, and outputs multiple signals capable of driving acoustic transducers to transmit sound waves. The acoustic field encoding module mainly includes a programmable gate array (FPGA) and supporting peripheral circuitry. By receiving instructions from the host computer, the FPGA directly generates drive signals or control signals to cause the chip to generate drive signals. These drive signals satisfy the helical phase modulation required to construct a perfect acoustic vortex, and can also superimpose amplitude, phase, and frequency modulations, supporting time-division multiplexing, space-division multiplexing, and frequency-division multiplexing technologies. The FPGA can integrate more computational functions: directional transmission of acoustic orbital angular momentum while keeping the transmitting equipment stationary, and simultaneous transmission in multiple directions; independent control of the radial intensity distribution of orbital angular momentum of each order; and anti-aliasing optimization between topological orders when the transmission array accuracy is low.

[0031] Based on the construction of a perfect vortex acoustic field by the acoustic orbit angular momentum emission array and the introduction of a rotating Doppler frequency shift by the rotating demultiplexer, amplitude, phase, or frequency modulation can be superimposed to realize acoustic orbit angular momentum multiplexed communication. This also ensures compatibility with other multiplexing technologies, such as time-division multiplexing, space-division multiplexing, and frequency-division multiplexing, simplifying hardware complexity and improving system compatibility. The FPGA controls each acoustic transducer unit in the phased array based on the driving signal calculated by the iterative optimization algorithm, thereby controlling the emission of acoustic orbit angular momentum and its radial intensity, as well as optimizing anti-aliasing between topological orders.

[0032] The sound field encoding module is compatible with the traditional communication module. After the FPGA records the modulation signal output by the traditional communication module, it adjusts the original signal through digital filtering, thereby multiplexing the original signal onto the acoustic track angular momentum.

[0033] The drive module includes power amplification and impedance matching functions. Both the power amplification factor and impedance are adjustable to accommodate different acoustic transducers. It should be noted that the power amplification and impedance matching functions can be implemented using any existing method.

[0034] Multiple acoustic transducers are arranged in an array, which can theoretically have any shape, and the FPGA can implement anti-aliasing optimization for its shape. In this embodiment, they are arranged in concentric ring arrays, spiral arrays, and uniform square arrays to facilitate anti-aliasing optimization.

[0035] Here, the rotary demultiplexer is further described, which includes a rotary motor, an acoustic sensor, a conductive slip ring, or a wireless signal transmitting device.

[0036] The acoustic sensor is used to receive acoustic signals; the rotary motor controls the rotation of the acoustic sensor to trigger the rotational Doppler effect, separating the angular momentum of acoustic vortices of different orders in the frequency domain. Then, by performing FFT (Fast Fourier Transform) analysis on the signals received by the acoustic sensor, the obtained frequency domain amplitude and phase information can be used to inversely determine the amplitude and phase information of the acoustic vortex. A conductive slip ring is used for wired transmission of the acoustic sensor signals. Alternatively, the acoustic sensor signals can be transmitted to a computer via wireless technologies such as Bluetooth or Wi-Fi.

[0037] It should be noted that a perfect acoustic vortex refers to a vortex whose beam radius does not change with the topological order of the acoustic orbital angular momentum; that is, acoustic orbital angular momentum of different topological orders is distributed on the same radius. If the orbital angular momentum of each order is not controlled to the same radius, the multiplexing effect of communication will be reduced, especially when the acoustic beam is coupled into a waveguide for propagation or propagates over long distances, the difference in beam radius will affect the demultiplexing effect.

[0038] Furthermore, the acoustic orbital angular momentum related theory of the present invention will be further explained:

[0039] First, the acoustic orbital angular momentum beam has a vortex wavefront, and the phase of the l-th order acoustic orbital angular momentum has l periodic changes along the circumferential direction. Its sound field can be described as follows:

[0040]

[0041] Where r is the radius, θ is the phase angle, t is the time variable, l is the topological order, and A l The amplitude of the l-th order acoustic orbital angular momentum. The phase of the l-th order acoustic orbital angular momentum. The phase representation in the circumferential direction (e... ilθ The orthogonality is reflected in formula (2), so different information can be loaded into the acoustic orbital angular momentum of different orders.

[0042]

[0043] Due to the multiplexing characteristics of acoustic orbital angular momentum communication, acoustic orbital angular momentum of different topological orders can be regarded as independent signal paths. The host computer distributes the data to be transmitted to different signal paths, and different distribution methods will be used for different application scenarios such as load balancing or parallel communication acceleration. At the same time, according to the data signal modulation method, such as amplitude shift keying (ASK), multilevel quadrature amplitude modulation (mQAM), frequency shift keying (FSK), phase shift keying (PSK), and multiphase phase shift keying (mPSK), the transmission parameters of acoustic orbital angular momentum, that is, the amplitude and phase of acoustic orbital angular momentum of each order, can be determined.

[0044] The acoustic field encoding module calculates the transmission parameters of the phased array (i.e., the transducer array) based on the acoustic trajectory angular momentum transmission parameters required for communication. The acoustic field encoding module calculates the transmission amplitude and phase of each transmitting element in the phased array through an iterative optimization algorithm. Based on the phased array's transmission parameters, the driver drives each element in the phased array to transmit ultrasonic waves with the required amplitude and phase, thereby constructing a perfect vortex acoustic field carrying multiplexing information.

[0045] The sound field encoding module can be a computer, a programmable gate array (FPGA), or other device with computing capabilities. The driver can use a commercial ultrasonic pulse transmitter chip, such as the TI TX7332, to drive the phased array; or it can use an FPGA, utilizing its I / O ports to generate binary encoded pulse signals to drive the transducers, and using MOSFETs to amplify the signals from the I / O ports to meet the backend load requirements. When the number of transmitting units in the phased array exceeds the number of I / O ports on the FPGA, a serial-to-parallel conversion can be performed using a shift register to expand the I / O ports.

[0046] Currently, two schemes are used in the experiment. Scheme 1: A computer is used to perform the calculation of the iterative optimization algorithm, and the phased array transmission parameters are sent to the driver via a universal serial bus (USB). The driver includes an FPGA, shift registers, and MOSFETs. The phased array used consists of 256 elements. The FPGA uses 32 I / O ports to generate binary encoded pulse signals. Each I / O port is connected to an 8-bit shift register. Through serial-to-parallel conversion, independent control of the 256 channels is achieved. 256 MOSFETs are used to independently amplify the signals of each channel to drive the ultrasonic transducers at the back end. Scheme 2: The sound field encoding module is implemented by an FPGA, that is, the FPGA in the driver replaces the computer to perform the calculation of the iterative optimization algorithm. The rest is the same as Scheme 1.

[0047] It should be noted that a phased array (i.e., a transducer array) can be a square array, a ring array, a spiral array, or other surface arrays.

[0048] The iterative optimization algorithm can be based on gradient optimization algorithm or global optimization algorithm such as genetic algorithm, and the objective function of the optimization algorithm is described in frequency domain form.

[0049] See Figure 2 The diagrams show the acoustic field and energy radius distribution of the multiplexed signal emitted by the acoustic orbital angular momentum emission array of this invention. The perfect acoustic fields obtained by the emission array for the second and fourth orders are shown respectively.

[0050] The process of the iterative optimization algorithm is further explained below:

[0051] First, initialize the complex amplitude (amplitude, phase) of the phased array and calculate the radiated sound field of the phased array. Initialization using the theoretical distribution described by the analytical formula is preferred: T(r,θ)=∑ l A l e ilθ The formula describes the superposition of acoustic trajectory angular momentum components of different (l) orders, where T(r,θ) represents the complex amplitude emitted by the transducer at different radii (r) and circumferential directions (θ), and A l The complex amplitude represents the l-th order acoustic trajectory angular momentum required for communication. The calculated radiated sound field is subjected to a Fourier transform in the circumferential direction (θ) to obtain the complex amplitude B(r,l,z) of the (l) order acoustic trajectory angular momentum in the sound field for different radii (r) and propagation distances (z).

[0052]

[0053] The spatial sound field distribution can be transformed from the above formula to the mathematical form of the frequency domain (sound track angular momentum domain) for the calculation of the objective function. Alternatively, additional constraints on the spatial sound field distribution can be added.

[0054] For example, if we want to obtain perfect vortices of order 1 and order 2 at r = r0 and z = z0, then the objective function can be set as:

[0055] MIN{∑ l＝1,2 [B(r0,l,z0)-A l ]},

[0056] The values ​​of r0 and z0 are usually related to the position of the rotation demultiplexer.

[0057] To ensure communication efficiency, suppress sidelobes, and concentrate the acquired energy on the perfect vortex, the objective function can also be described in the frequency domain.

[0058] For example: if we want to reduce interference components other than the first and second orders in a perfect vortex.

[0059] MIN{∑ l≠1,2 B(r0,l,z0)},

[0060] If the goal is to reduce the acoustic orbital angular momentum beyond the radius of the perfect vortex, then...

[0061] MIN{∑ l [B(r≠r0,l,z0)]}

[0062] The examples above are only 1 and 2. In actual use, the reuse order can be freely chosen. For example, a 16x16 array can be used to achieve acoustic orbital angular momentum reuse from -4th to 4th order. Furthermore, the objective function can be adjusted according to the actual situation, and objective functions with different functions can be combined mathematically.

[0063] The rotating demultiplexer separates the acoustic trajectory angular momentum information in the frequency domain of the received signal by introducing the rotating Doppler effect. During communication, the axis of the rotating demultiplexer should be aligned with the axis of the transmitted acoustic trajectory angular momentum. Besides mechanical alignment, the midpoint of the transmitted acoustic trajectory angular momentum can be dynamically adjusted in an iterative optimization algorithm to track the rotating demultiplexer and achieve good alignment. After alignment, the motor is set to rotate at a constant angular velocity Ω (rad / s). The faster the rotation speed, the better the demultiplexing effect theoretically, but this also places higher demands on system accuracy, such as the stability of the mechanical system. The signal received by the rotating sensor is transmitted to a personal computer for further processing via a conductive slip ring (or a wireless signal transmitter). The amplitude and phase of the acoustic trajectory angular momentum are obtained through Fourier transform of the signal. Based on the signal modulation method and encoding rules, the communication data is finally obtained, completing the entire communication process.

[0064] Preferably, the rotating motor in the rotary demultiplexer should be programmable, allowing for dynamic speed adjustment, and also possess a speed stabilization function. High speed stability is essential to ensure effective demultiplexing.

[0065] The principle of the rotating demultiplexer for processing the received signal is as follows: According to formula (1): The sound field distribution described is given by the signal s(t) received by a sensor rotating at a speed of Ω (rad / s):

[0066]

[0067] It can be seen that the angular frequency of the received signal corresponding to order l is ω + lΩ. That is, a Doppler frequency offset of lΩ is generated based on the signal transmission frequency ω. When the rotational speed Ω is constant, there is a one-to-one correspondence between the Doppler frequency offset and the order l. Moreover, the amplitude and phase of the received signal are both consistent with formula (1): p(r,θ,t)= The amplitude and phase of the acoustic orbital angular momentum are consistent. Therefore, Fourier transform can be used to extract the amplitude and phase of the received signal s(t) and invert the amplitude and phase of the acoustic orbital angular momentum.

[0068] The multiplexing characteristic is thus demonstrated: switching the phased array's transmission parameters once allows for the transmission of multiple signals, and the multiplexing performance is related to the number of acoustic orbital angular momentum used. For example, multiplexing 20 orders of acoustic orbital angular momentum (1 to 20) results in a communication system with 20 times the performance of the original system. This is because changing the phased array's transmission parameters once allows for the transmission of 20 signals, leading to high communication efficiency. A single-sensor scheme based on rotating Doppler can simultaneously demultiplex these multiple signals using only one sensor, significantly reducing system complexity compared to traditional array receivers.

[0069] Preferably, based on the single-sensor rotation demultiplexer, it is combined with Multiple-Input Multiple-Output (MIMO) technology. On the one hand, the rotation of a single sensor can be changed to a scheme of coaxial rotation of multiple sensors, that is, a motor drives multiple sensors to rotate. On the other hand, the simultaneous application of multiple sets of rotation communication systems increases the number of signal links, which can effectively improve system capacity, coverage and signal-to-noise ratio, as well as improve the performance of acoustic-orbit angular momentum communication in atmospheric turbulence and underwater turbulence.

[0070] Second Embodiment

[0071] Based on the same concept, this invention also provides a rotating Doppler-based acoustic orbital angular momentum multiplexing communication method, applied to the aforementioned rotating Doppler-based acoustic orbital angular momentum multiplexing communication system, comprising the following steps: controlling the rotation of the acoustic sensor of the rotating demultiplexer to acquire the acoustic orbital angular momentum multiplexing signal that satisfies a perfect acoustic vortex emitted by the acoustic orbital angular momentum emission array to achieve separation of acoustic orbital angular momentum in the frequency domain; wherein, the acoustic orbital angular momentum multiplexing signal is obtained based on preset phased array emission parameters through a preset gradient optimization algorithm or genetic optimization algorithm; performing a Fourier transform on the acoustic orbital angular momentum multiplexing signal to obtain the amplitude and phase of the acoustic orbital angular momentum, and decoding based on a preset signal modulation method and encoding rules to obtain communication data.

[0072] This embodiment constructs a perfect vortex sound field, concentrating energy at a single radius, thus avoiding energy dispersion, improving reception efficiency, and consequently enhancing communication efficiency based on acoustic orbital angular momentum. The rotating demultiplexer in this embodiment receives orbital angular momentum multiplexed signals while continuously rotating around a preset axis. This introduces a rotating Doppler frequency shift, enabling the separation of orbital angular momentum signals of different topological orders within the composite signal, thereby extracting the information carried by each order. This achieves improved communication efficiency based on acoustic orbital angular momentum while reducing the complexity of the acoustic orbital angular momentum multiplexing communication system.

[0073] Preferably, when the axis of rotation of the acoustic sensor is not aligned with the axis of acoustic orbit angular momentum emission, the midpoint of the emitted acoustic orbit angular momentum is dynamically adjusted in the gradient optimization algorithm or genetic optimization algorithm to track the rotating multiplexer and thus achieve a good alignment effect.

[0074] By correcting the direction or position of the rotation axis of the acoustic sensor relative to the axis of acoustic orbit angular momentum emission, the accuracy of the system signal transmission can be further improved.

[0075] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A sound orbital angular momentum multiplexing communication system based on rotational Doppler, characterized in that, It comprises: An acoustic orbital angular momentum transmitting array and a rotation demultiplexer, the acoustic orbital angular momentum transmitting array is used to construct perfect acoustic vortexes with acoustic orbital angular momentum signals with different topological orders to combine into one acoustic orbital angular momentum multiplexing signal transmitted on the same channel at the same time, and the rotation demultiplexer is used to demultiplex the received acoustic orbital angular momentum multiplexing signal transmitted on the same channel at the same time based on the rotational Doppler to extract the information carried in each order signal; wherein the central axis of the acoustic sensor of the rotation demultiplexer coincides with the preset first axis.

2. The rotation-Doppler based acoustic orbital angular momentum multiplexing communication system of claim 1, wherein, The acoustic orbital angular momentum transmitting array comprises a sound field encoding module, a driving module and a phased array composed of a plurality of independently controlled acoustic transducer units, the sound field encoding module encodes and multiplexes the information to be transmitted onto acoustic orbital angular momentum signals with different orders and outputs a plurality of driving signals based on a preset program, and the plurality of acoustic transducer units in the phased array are driven by the driving module to transmit acoustic orbital angular momentum multiplexing signals satisfying perfect acoustic vortexes.

3. The rotation-Doppler based acoustic orbital angular momentum multiplexing communication system of claim 2, wherein, The sound field encoding module is realized based on FPGA, the FPGA receives the host computer instruction and calculates the driving signal including the transmission amplitude and phase based on the iterative optimization algorithm, and the objective function of the iterative optimization algorithm is described by the mathematical form of the spatial domain and the frequency domain; the driving module drives each acoustic transducer unit in the phased array to transmit ultrasonic waves with the required amplitude and phase to construct a perfect vortex sound field carrying multiplexing information based on the transmission amplitude and phase, wherein the driving signal satisfies the spiral phase modulation required for constructing perfect acoustic vortexes.

4. The rotation-Doppler based acoustic orbital angular momentum multiplexing communication system of claim 3, wherein, The driving signal is superimposed with amplitude or phase or frequency modulation to realize acoustic orbital angular momentum multiplexing communication, and is compatible with time division multiplexing, space division multiplexing and frequency division multiplexing; or, the driving signal is superimposed with a multiple-input multiple-output system, when a plurality of transmitting arrays or a plurality of sensors or a plurality of rotating devices are used, a multiple-input multiple-output system is constructed to improve the communication effect.

5. The rotation-Doppler based acoustic orbital angular momentum multiplexing communication system of claim 3, wherein, The FPGA controls each acoustic transducer unit in the phased array according to the driving signal calculated by the iterative optimization algorithm to realize the transmission or not of acoustic orbital angular momentum and the control of radial intensity, and the anti-aliasing optimization between topological orders. 6.The rotational Doppler-based acoustic orbital angular momentum multiplexing communication system of claim 3, wherein, The plurality of acoustic transducer units in the phased array are arranged in concentric circular ring arrays or spiral arrays or uniform square arrays.

7. The rotation-Doppler based acoustic orbital angular momentum multiplexing communication system of claim 1, wherein, The rotation demultiplexer comprises a rotating device and an acoustic sensor mounted on the rotating device, the rotating device controls the rotation of the acoustic sensor to realize the separation of the received acoustic orbital angular momentum in the frequency domain based on the rotational Doppler effect, and then perform FFT analysis to obtain the amplitude and phase information of the frequency domain amplitude and phase inversion acoustic vortex. 8.The rotational Doppler-based acoustic orbital angular momentum multiplexing communication system of claim 1, wherein, The acoustic sensor is connected with the rotating motor on the rotating device through a conductive slip ring, and the conductive slip ring transmits the signal of the acoustic sensor to a signal processing device; or, a wireless communication device is arranged on the acoustic sensor, and the wireless communication device transmits the signal of the acoustic sensor to a signal processing device. 9.A method for acoustic orbital angular momentum multiplexing communication based on rotational Doppler, characterized in that, The application is applied to the acoustic orbital angular momentum multiplexing communication system based on rotational Doppler in any one of claims 1-8, comprising the following steps: The acoustic sensor rotation controls the rotation demultiplexer to obtain the acoustic orbital angular momentum multiplexing signal emitted by the acoustic orbital angular momentum emission array to realize the separation of the acoustic orbital angular momentum in the frequency domain, wherein the acoustic orbital angular momentum multiplexing signal is generated by controlling the phased array emission based on the preset gradient optimization algorithm or genetic algorithm and the arrangement mode and emission performance parameters of the preset phased array; The acoustic orbital angular momentum multiplexing signal is rotated and received, the received signal is subjected to Fourier transform to obtain the amplitude and phase of the acoustic orbital angular momentum, and the communication data is obtained based on the preset signal modulation mode and coding rule decoding.

10. The rotation-Doppler based acoustic orbital angular momentum multiplexing communication method of claim 9, wherein, When the axis of the acoustic sensor rotation is not aligned with the axis of the acoustic orbital angular momentum emission, the midpoint of the emitted acoustic orbital angular momentum is dynamically adjusted in the gradient optimization algorithm or genetic optimization algorithm according to the quality of the received signal to track the rotation multiplexer, thereby realizing good alignment effect.

Images