Mixing acoustic demodulator based on curling structure and use method thereof

Abstract

The invention discloses a frequency mixing sound demodulator based on a curled structure and a use method thereof in the acoustics field, the demodulator is used for separating frequency mixing sound mixed by a plurality of sound waves with preset frequencies according to respective frequencies, and the demodulator comprises an air waveguide for transmitting the sound waves, and blocking structures arranged on two sides of the air waveguide for blocking the sound waves from penetrating, and a plurality of curled structures that capture corresponding preset frequency sound waves; curled structures are arranged in the barrier structure on at least one side of the air waveguide at intervals, one end of each curled structure is open, and the other side is closed; a plurality of cross beams for blocking penetration of sound waves are arranged in each curled structure, and an internal channel of each curled structure is divided into different lengths to serve as different acoustic resonant cavities so as to capture the sound waves with different frequencies; the closed end of each curled structure is a detection end of each preset frequency sound wave. The invention solves the problem that the existing method is difficult to instantly separate the frequency mixing sound signal and carry out information transmission.

Description

Technical Field

[0001] This invention relates to the field of acoustics, and in particular to a mixer demodulator based on a coiled structure and its usage method. Background Technology

[0002] In recent years, acoustic metamaterials have attracted widespread attention due to their unique ability to manipulate sound waves, particularly in the fields of acoustic signal processing and information transmission, where they have demonstrated enormous potential. Traditional acoustic signal demodulation techniques typically rely on complex electronic devices and digital signal processing algorithms, which not only increases system complexity but also limits their application in real-time processing. Therefore, exploring acoustic signal demodulation methods based on physical structures has become a research hotspot.

[0003] In acoustic signal demodulation, the separation and demodulation of mixed acoustic signals is one of the key challenges. While traditional frequency division multiplexing (FDM) techniques can achieve parallel transmission of multi-frequency signals, their reliance on electronic filters and digital signal processing makes them difficult to meet the demands of compactness and real-time processing. In recent years, the discovery of acoustic rainbow capture has provided a new approach to solving this problem. By designing gradient refractive index structures or resonant units, sound waves of different frequencies can be spatially separated and captured, thus achieving physical spectral separation. Acoustic labyrinth structures, as high-refractive-index acoustic metamaterials, can effectively reduce the group velocity of sound waves and enhance the interaction between sound waves and the structure by extending the sound wave propagation path through spatial curling. This structure not only enables slow-wave propagation of sound waves but also achieves frequency-selective capture through resonance effects. Although existing research has made some progress in acoustic rainbow capture and spectral separation, how to apply these techniques to the real-time demodulation and information transmission of mixed acoustic signals remains an open question. Summary of the Invention

[0004] The purpose of this invention is to provide a mixer demodulator based on a coiled structure and its usage method, which solves the problem that existing methods are difficult to separate and transmit information in real time from the mixer sound signal.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0006] In a first aspect, the present invention provides a mixer demodulator based on a coiled structure for separating a mixed sound of multiple preset frequency sound waves according to their respective frequencies, comprising: an air waveguide for transmitting sound waves, an isolation structure disposed on both sides of the air waveguide to block the penetration of sound waves, and multiple coiled structures for capturing sound waves of corresponding preset frequencies; the air waveguide has at least one isolation structure on one side with coiled structures spaced apart, the end of the coiled structure near the air waveguide being open and the other side away from the air waveguide being closed; each coiled structure has multiple crossbeams built in it to block the penetration of sound waves, which respectively divide the internal channel of each coiled structure into different lengths to serve as different acoustic resonant cavities to capture sound waves of different frequencies; the closed ends of each coiled structure are the detection ends of the sound waves of each preset frequency.

[0007] In the aforementioned mixer demodulator based on a coiled structure, the length of the internal channels of the multiple coiled structures that capture the corresponding preset frequency sound waves is one-quarter of the wavelength of the corresponding preset frequency sound waves; the minimum frequency interval between the preset frequency sound waves is greater than 5 times the bandwidth of each coiled structure; the bandwidth of the coiled structure is obtained by drawing a horizontal line 3dB downward from the peak of the resonant cavity frequency response curve, which intersects the curve at two points f1 and f2, where f1 < f2, and the bandwidth Δf = f2 - f1.

[0008] The aforementioned mixer demodulator based on a coiled structure has a spacing of the coiled structure that is set to a preset sound insulation value according to the lowest preset frequency in the mixer sound.

[0009] In the aforementioned mixer demodulator based on a coiled structure, when the width of the internal channels of each coiled structure is the same and the dimensions of each crossbeam are the same, each coiled structure is arranged in order of high to low frequency of the captured sound wave; when coiled structures are respectively arranged in the barrier structures on both sides of the air waveguide, the coiled structures on one side of the air waveguide are arranged in the forward order of the captured sound wave frequency, and the coiled structures on the other side of the air waveguide are arranged in the reverse order of the captured sound wave frequency.

[0010] In the aforementioned mixer demodulator based on a coiled structure, when coiled structures are respectively installed in the blocking structures on both sides of the air waveguide, the boundaries of the air waveguide adjacent to the blocking structures on both sides are parallel and the spacing distance is greater than one-quarter of the wavelength of the lowest preset frequency sound wave in the mixer.

[0011] The aforementioned mixer demodulator based on a coiled structure is used to preset a first frequency sound wave, a second frequency sound wave, a third frequency sound wave, a fourth frequency sound wave, a fifth frequency sound wave, and a sixth frequency sound wave with sequentially decreasing frequencies. When the mixed sound of the six preset frequency sound waves is separated according to their respective frequencies, a coiled structure is respectively provided in the blocking structure on both sides of the air waveguide; a coiled structure for capturing the first frequency sound wave, a coiled structure for capturing the second frequency sound wave, and a coiled structure for capturing the third frequency sound wave are sequentially provided in the blocking structure on one side of the air waveguide; a coiled structure for capturing the sixth frequency sound wave, a coiled structure for capturing the fifth frequency sound wave, and a coiled structure for capturing the fourth frequency sound wave are sequentially provided in the blocking structure on the other side of the air waveguide.

[0012] The aforementioned mixer demodulator based on a coiled structure, when used to separate the mixed sound from six preset frequency sound waves (4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz, and 9700Hz) according to their respective frequencies, has internal channel lengths of 18.245mm, 15.044mm, and 15.044mm respectively for capturing the preset frequencies of 4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz, and 9700Hz within the coiled structure. The dimensions are 14.057mm, 12.25mm, 10.586mm, and 8.84mm; A coiled structure is set inside the barrier structure on both sides of the air waveguide. The boundaries of the barrier structures on both sides are parallel to the air waveguide and are spaced apart by a distance of 2.67mm. The interval between the coiled structures is 3mm. The coiled structure is a rectangular structure with a width of 0.375mm. The width of the channel inside the coiled structure is 0.025mm, and the width of the crossbeam is 0.025mm and the length is 0.35mm.

[0013] Secondly, the present invention provides a method for using a mixer-demodulator based on a coiled structure, wherein the mixer-demodulator based on a coiled structure described in the first aspect is used for information transmission, including:

[0014] Select the preset frequencies that make up the mixing sound according to the information transmission target and preset the corresponding transmission rules;

[0015] The preset frequency sound wave is input from one end of the air waveguide according to the preset transmission rules, and is detected from the detection end of the preset frequency sound wave through each coil structure, and the corresponding sound pressure amplitude information is output.

[0016] The detected sound pressure level information is converted into target information.

[0017] The aforementioned method for using a converging structure-based mixer demodulator involves transmitting information to a binary sequence and image information based on the binary sequence. When the information transmission target is a binary sequence, 1 indicates the presence of a preset frequency sound wave, and 0 indicates the absence of a preset frequency sound wave. The binary sequence is transmitted unit by unit until the binary sequence transmission is complete. When the information transmission target is image information, the image information is converted into a binary pixel grid, where 1 represents colored pixels and 0 represents colorless pixels. The binary pixel grid is then converted into multiple binary sequences, and each binary sequence is transmitted separately.

[0018] The aforementioned method for using a convoluted structure-based mixer demodulator involves transmitting information using the convoluted structure-based mixer demodulator described in the first aspect. When the information transmission target is one of the six three-bit binary numbers 001, 010, 011, 100, 101, and 110, sound waves at 4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz, and 9700Hz are selected to form the mixer sound, which is then transmitted as 001, 010, 011, 100, 101, and 110, respectively. The transmission rules include: in the first second, Input a mixed sound composed of 7000Hz, 8100Hz and 9700Hz sound waves; at the second second, input a mixed sound composed of 5700Hz, 6200Hz and 9700Hz sound waves; at the third second, input a mixed sound composed of 4700Hz, 6200Hz and 8100Hz sound waves; input the preset frequency sound waves from one end of the air waveguide (1) according to the preset transmission rules, detect the time domain response of the sound pressure signal from the detection end of each preset frequency sound wave, and output the corresponding sound pressure amplitude information; convert the detected sound pressure amplitude information into 6 target three-bit binary numbers.

[0019] Beneficial effects:

[0020] Compared with the prior art, the present invention has the following advantages and advancements:

[0021] This invention relates to a mixer demodulator based on a coiled structure. By designing a coiled structure and utilizing multiple crossbeams inside the coiled structure to block sound wave penetration, the internal channels of each coiled structure are divided into different lengths, resulting in a coiled structure matching a preset frequency as an acoustic resonant cavity. This cavity is used to separate the mixed sound of multiple preset frequency sound waves according to their respective frequencies. Frequency division multiplexing and information transmission of the mixed sound are achieved using only physical structure, solving the problem that existing methods are unable to separate and transmit mixed sound signals in real time.

[0022] The present invention provides a frequency-modulated acoustic mixer based on a coiled structure that demodulates instantly without requiring additional digital signal processing. This "structure as function" design concept breaks through the dependence of traditional signal processing on electronic devices and algorithms, and realizes the instantaneous completion of the entire physical process from sound wave incidence to spectrum separation, which significantly simplifies the signal processing flow and improves demodulation efficiency.

[0023] The present invention relates to a mixer-demodulator based on a coiled structure. By designing a compact spatial arrangement of coiled channels distributed on both sides and selecting six units corresponding to specific frequencies to construct a demodulation array, it achieves spatial separation and information demodulation of multi-frequency sound waves. Analysis of the sound wave dispersion relation shows that this structure extends the sound wave propagation path through a high-refractive-index acoustic metamaterial, significantly reducing the group velocity and enhancing the localization of sound waves. This allows sound waves of different frequencies to be captured at the units corresponding to the cutoff frequencies, thereby achieving physical separation of the spectrum.

[0024] The present invention's coil-structure-based mixer demodulator effectively separates sound waves of six frequencies within the range of 4700Hz to 9700Hz. Each frequency component is precisely confined to its corresponding channel, exhibiting significant energy localization and rainbow capture effects. Time-domain signal excitation further verifies the demodulation capability of this structure for multi-frequency mixed signals, and the performance of the demodulator is highlighted by transmitting an "NJ" signal: each channel responds significantly only to its own resonant frequency, achieving frequency division multiplexing and physical discrimination of signal content, enabling real-time demodulation without relying on external digital processing.

[0025] This invention's coiled structure-based mixer-demodulator achieves parallel processing and transmission of multiple acoustic signals at the subwavelength scale, combining the advantages of compact structure, instantaneous response, and physical demodulation, overcoming the limitations of traditional electronic demodulation methods in terms of complexity and real-time performance. Subwavelength refers to the fact that the size of each coiled structure is smaller than the operating wavelength of the captured frequency sound wave. This coiled structure-based mixer-demodulator provides a new approach for the application of acoustic metamaterials in communication and signal processing, and has particularly broad prospects in acoustic sensing, filtering, and low-power information demodulation systems. Attached Figure Description

[0026] Figure 1 This is a two-dimensional structural schematic diagram of a mixer-demodulator based on a coiled structure according to Embodiment 1 of the present invention;

[0027] Figure 2 This is a schematic diagram of a two-dimensional arrangement of a coiled structure 3 of a mixer-demodulator based on a coiled structure according to Embodiment 1 of the present invention.

[0028] Figure 3 This is a schematic diagram of the dispersion relationship and mixing sound group velocity of the coiled structure under different internal channel lengths of the mixer demodulator based on the coiled structure in Embodiment 1 of the present invention.

[0029] Figure 4 This is a schematic diagram of the normalized amplitude distribution of sound waves of each preset frequency propagating from left to right along the air waveguide in the frequency mixer demodulator based on the curled structure of Embodiment 1 of the present invention.

[0030] Figure 5 This is a schematic diagram of the time-domain signals received by each channel in the method of using the mixer demodulator based on the curled structure according to Embodiment 2 of the present invention;

[0031] Figure 6 A schematic diagram of the output response at the bottom of the six demodulation channels and the demodulated signal image of a method for using a mixer demodulator based on a coiled structure according to Embodiment 2 of the present invention;

[0032] Figure 7 A schematic diagram of the output response at the bottom of the six demodulation channels and the demodulated signal image of a method for using a mixer demodulator based on a coiled structure according to Embodiment 2 of the present invention;

[0033] Explanation of reference numerals in the attached figures:

[0034] 1-Air waveguide; 2-Barrier structure; 3-Rolled structure; 4-Crossbeam. Detailed Implementation

[0035] The technical solutions of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The following description of at least one exemplary embodiment is merely illustrative and is in no way intended to limit the present invention or its application or use.

[0036] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only used to explain the relative positional relationship and movement between components in a specific posture. If the specific posture changes, the directional indication will also change accordingly. These terms are used only for the convenience of describing the invention and for simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limiting the invention. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0037] Example 1

[0038] This embodiment introduces a mixer demodulator based on a coiled structure, used to separate mixed sound from multiple preset frequency sound waves according to their respective frequencies, such as... Figure 1As shown, the device includes an air waveguide 1 for transmitting sound waves, an isolation structure 2 disposed on both sides of the air waveguide 1 to block the penetration of sound waves, and multiple coiled structures 3 for capturing sound waves of corresponding preset frequencies. At least one side of the air waveguide 1 has an isolation structure 2 containing a coiled structure 3. The coiled structure 3 is open at one end near the air waveguide 1 and closed at the other end away from the air waveguide 1. Multiple crossbeams 4, built into each coiled structure 3, block the penetration of sound waves, dividing the internal channels of each coiled structure 3 into different lengths to serve as different acoustic resonant cavities for capturing sound waves of different frequencies. The closed ends of each coiled structure 3 are detection ends for sound waves of each preset frequency.

[0039] The internal channel lengths of the multiple coiled structures 3 that capture sound waves of corresponding preset frequencies are each one-quarter of the wavelength of the sound wave at that preset frequency. For a wave to exist stably within a cavity, its fundamental mode resonance mode must satisfy the following condition: the distance from the entrance (node) to the end (antinode) must be exactly one-quarter of the wavelength (λ / 4). The physical boundary condition of the coiled structure 3, with one end open and the other closed, naturally determines this resonance mode. The coiled structure 3 can most effectively achieve strong acoustic energy localization within a compact size, thereby allowing each channel to produce an extremely high response to a specific frequency. Figure 1 As shown by the black line with arrows in the right sub-figure, the internal channel length of the curled structure 3 refers to the overall channel centerline length formed by connecting the beginning and end of the centerlines at various points within the internal channel.

[0040] The minimum frequency interval between the preset frequency sound waves is greater than 5 times the bandwidth of each curled structure 3; the bandwidth of the curled structure 3 is drawn horizontally 3 dB down from the peak of the resonant cavity frequency response curve, intersecting the curve at two points f1 and f2, where f1 < f2, and the bandwidth Δf = f2 - f1.

[0041] In an acoustic resonant cavity system, the bandwidth Δf of each coiled structure 3 needs to be determined first through calculation or experiment. Then, based on a preset frequency rule that the minimum frequency interval between sound waves of a preset frequency is greater than 5 times the bandwidth of each coiled structure 3, it is verified whether the preset frequencies of all sound waves to be separated conform to the preset frequency rule. Only when the preset frequencies of each sound wave in the mixed sound to be separated conform to the preset frequency rule can it be ensured that each coiled structure 3 responds effectively to only one frequency, thus achieving the separation of sound waves of the preset frequency. The preset frequency rule is used to suppress interference between frequencies and ensure the single-frequency selectivity of each coiled structure 3.

[0042] like Figure 1 As shown, the spacing d2 of the interlaced coiled structures 3 is set according to the lowest preset frequency in the mixing sound to meet the preset sound insulation amount. In this embodiment, the preset sound insulation amount is 30dB. The spacing d2 should ensure that the sound insulation amount of the barrier structure 2 between the two interlaced coiled structures 3 is greater than 30dB, so as to reduce the crosstalk effect of adjacent acoustic resonant cavities. In this embodiment, the volume density ρ of the barrier structure 2 is 7800kg / m³.3 The spacing d2 is 2mm, or 0.002m. The surface density m = ρ × d2, therefore the surface density m of barrier structure 2 is calculated to be 15.6 kg / m³. 2 Minimum sound insulation R min =20lg(mf min )−48,f min In this embodiment, f is the lowest preset frequency in the mixing sound. min =4700Hz, minimum sound insulation R min =20lg(15.6×4700)−48, approximately 49.3 dB, which is greater than 30 dB and meets the design requirements.

[0043] When the width of the internal channels of each coiled structure 3 is the same and the dimensions of each crossbeam 4 are the same, the coiled structures 3 are arranged sequentially according to the preset frequency of the captured sound waves. When coiled structures 3 are respectively arranged in the blocking structures 2 on both sides of the air waveguide 1, the coiled structures 3 on one side of the air waveguide 1 are arranged in ascending order according to the preset frequency of the captured sound waves, and the coiled structures 3 on the other side of the air waveguide 1 are arranged in descending order according to the preset frequency of the captured sound waves. This design makes the mixer demodulator based on the coiled structure in this embodiment compact, stable and orderly.

[0044] like Figure 1 As shown, when the blocking structures 2 on both sides of the air waveguide 1 are respectively provided with coiled structures 3, the boundaries of the air waveguide 1 adjacent to the blocking structures 2 on both sides are parallel and spaced apart, that is, as shown in the figure. Figure 1 The width w2 of the air waveguide 1 shown is greater than one-quarter of the wavelength of the lowest preset frequency sound wave in the mixing sound. This is also to avoid mutual interference between the various coiled structures 3.

[0045] Figure 1 This is only a structural schematic diagram and does not represent the actual number and size of the horizontal plates 4 inside each coiled structure 3; since the width of the internal channels of each coiled structure 3 is the same and the size of each horizontal beam 4 is the same, but the length of the internal channels of each coiled structure is different, then... Figure 2 As shown, the height h of each coiled structure 3 is different; to match the different coiled structure heights, when the air waveguide 1 is horizontal, the boundary where the closed end of the coiled structure 3 is located is inclined; when the air waveguide 1 is inclined, the boundary where the closed end of the coiled structure 3 is located is horizontal; as shown Figure 2 As shown, in order to make the overall structure of the mixer demodulator based on the coiled structure in this embodiment smaller, the air waveguide 1 is inclined while maintaining the width w2. Additionally, Figure 1 and Figure 2This is only a two-dimensional structural diagram. In actual applications, the mixer demodulator based on the curled structure in this embodiment can be transformed into a three-dimensional structure of corresponding thickness (not shown in the figure) according to actual application requirements. This three-dimensional structure can also be built into a corresponding shell (shown in the figure).

[0046] In one specific embodiment, such as Figure 1 As shown, the preset frequencies of the sound waves are sequentially decreasing: a first frequency of 9700Hz, a second frequency of 8100Hz, a third frequency of 7000Hz, a fourth frequency of 6200Hz, a fifth frequency of 5700Hz, and a sixth frequency of 4700Hz. When the mixed sound of the six preset frequency sound waves is separated according to their respective frequencies, a curling structure 3 is respectively provided in the blocking structure 2 on both sides of the air waveguide 1.

[0047] Inside the barrier structure 2 on one side of the air waveguide 1, a coiled structure 3 for capturing the first frequency sound wave 9700Hz is arranged sequentially as channel one, a coiled structure 3 for capturing the second frequency sound wave 8100Hz is arranged as channel two, and a coiled structure 3 for capturing the third frequency sound wave 7000Hz is arranged as channel three.

[0048] On the other side of the air waveguide 1, within the barrier structure 2, a coiled structure 3 is sequentially arranged to capture the sixth frequency sound wave 4700Hz as channel six, a coiled structure 3 to capture the fifth frequency sound wave 5700Hz as channel five, and a coiled structure 3 to capture the fourth frequency sound wave 6200Hz as channel four.

[0049] When the frequency of the sound wave matches the resonant frequency of the channel, a sound pressure antinode is formed at the bottom of the channel and a node is formed at the entrance. The sound wave energy is strongly localized inside the channel, achieving "capture" of specific frequencies. Combined with gradient depth design, the resonant frequencies of the six channels correspond to 4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz and 9700Hz respectively, thereby achieving spatial separation of multi-frequency sound waves.

[0050] like Figure 3 The left sub-figure shows the acoustic dispersion curves of channel elements at different depths, calculated using the finite element method. The horizontal axis represents the normalized wave vector, and the vertical axis represents the frequency. The wave vector kx itself is a physical quantity describing the propagation direction and phase change rate of the sound wave in the structure, and it changes dynamically with frequency and structural parameters. The black line in the figure represents the dispersion curve of air, and the curves from top to bottom represent the dispersion curves of each channel with gradually increasing depth. The analysis results show that all acoustic dispersion curves have similar variation patterns: in the region with a small wave vector, the acoustic dispersion curve almost coincides with the air dispersion curve; as the wave vector increases, the acoustic dispersion curve gradually deviates from the air dispersion line and becomes increasingly flat. When the wave vector approaches the boundary of the Brillouin zone, the dispersion curve tends to be horizontal. Figure 3In this context, π / a refers to the upper limit of the analysis range of the wave vector kx, which is π / a, i.e., the boundary of the first Brillouin zone, where a is the lattice constant. In this embodiment, the lattice constant is 2 cm.

[0051] The expression for the group velocity of sound wave propagation:

[0052]

[0053] In the formula, Angular frequency, , For wave vector, = / λ, λ=c / f, where c is the speed of sound in air, and in this embodiment, the value is taken as 343m / s.

[0054] It is known that for a sound wave of a specific frequency, the group velocity gradually decreases with increasing propagation distance, eventually approaching zero. A horizontal dispersion curve indicates that the group velocity is close to zero, and the sound wave can no longer propagate forward. The frequency corresponding to this point is the sound wave cutoff frequency. Figure 3 As shown in the right sub-figure, the incident wave travels a shorter distance with increasing operating frequency, stopping at a shallower point in the channel. Therefore, the spatial evolution of the group velocity reveals the strong dispersion behavior of the mixer / demodulator based on the coiled structure in this embodiment.

[0055] like Figure 1 As shown, the structural parameters of the mixer demodulator based on the curled structure include: the curled structure 3 is a rectangular structure with a width t = 0.375 mm; the interval distance d2 of the curled structures 3 is set at 3 mm, which is greater than the value of 1.82 mm. As shown in Table 1, the internal channel lengths of the six coiled structures are as follows: Channel 1 internal channel length L1 = 8.84 mm, Channel 2 internal channel length L2 = 10.586 mm, Channel 3 internal channel length L3 = 12.25 mm, Channel 4 internal channel length L4 = 14.057 mm, Channel 5 internal channel length L5 = 15.044 mm, and Channel 6 internal channel length L6 = 18.245 mm; the width of beam 4 is d1 = 0.025 mm; the width of the internal channel of coiled structure 3 is w1 = 0.025 mm; the width of air waveguide 1 is w2 = 2.67 mm, which is greater than the value of 1.82 mm. The density of air is 1.21 kg / m³. 3 The sound velocity is 343 m / s; the barrier structure 2 uses materials with a density of 7800 kg / m³. 3 A rigid material with a sound velocity of 1635 m / s. Rigid materials are those with very high acoustic impedance, which can effectively reflect sound wave energy back while absorbing or transmitting very little sound energy themselves.

[0056] Table 1. Parameter correspondence of the curled structure for capturing preset frequency sound waves.

[0057] aisle Preset frequency f (Hz) Internal channel length L (mm) Operating wavelength (mm) Channel 1 9700 8.84 35.361 Channel Two 8100 10.586 42.346 Channel 3 7000 12.25 49 Channel 4 6200 14.057 56.230 Channel 5 5700 15.044 60.175 Channel Six 4700 18.245 72.979

[0058] In the finite element simulation software, the research frequency is set from 4000Hz to 10000Hz, with a step size of 100Hz, and the sound source is placed at the leftmost end of the air waveguide 1. Figure 4 The amplitude distribution diagrams for six different frequencies (4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz, and 9700Hz) are shown, with all sound field distributions normalized to their maximum values. The sound waves at these three frequencies are all well excited and propagate to the right. Different frequency components eventually stop propagating to the right in regions at different depths, while the sound wave energy reaches its maximum near the corresponding locations. This achieves spatial separation of sound waves of different frequencies, trapping them at different locations within the waveguide, consistent with previous predictions from the dispersion relation diagram.

[0059] Example 2

[0060] This embodiment describes a method for using a frequency mixer demodulator based on a coiled structure. Information transmission is performed using the frequency mixer demodulator based on a coiled structure described in Embodiment 1, including:

[0061] Select the preset frequencies that make up the mixing sound according to the information transmission target and preset the corresponding transmission rules;

[0062] The preset frequency sound wave is input from one end of the air waveguide 1 according to the preset transmission rules, and is detected from the detection end of each preset frequency sound wave through each curling structure 3, and the corresponding sound pressure amplitude information is output.

[0063] The detected sound pressure level information is converted into target information.

[0064] The information transmission targets include binary sequences and image information based on binary sequences;

[0065] When the information transmission target is a binary sequence, 1 indicates that there is a preset frequency sound wave, and 0 indicates that there is no preset frequency sound wave. The binary number is transmitted in sequence until the binary sequence transmission is completed.

[0066] When the information transmission target is image information, the image information is converted into a binary pixel grid, where 1 represents a colored pixel and 0 represents a colorless pixel; the binary pixel grid is then converted into multiple binary sequences, and each binary sequence is transmitted separately.

[0067] In one specific embodiment, when the information transmission target is one of the six three-bit binary numbers: 001, 010, 011, 100, 101, and 110,

[0068] Based on the information transmission target, sound waves of 4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz, and 9700Hz are selected to form a mixed sound, which is used to transmit 001, 010, 011, 100, 101, and 110 respectively. The transmission rules are as follows: in the first second, a mixed sound composed of sound waves of 7000Hz, 8100Hz, and 9700Hz is input; in the second second, a mixed sound composed of sound waves of 5700Hz, 6200Hz, and 9700Hz is input; and in the third second, a mixed sound composed of sound waves of 4700Hz, 6200Hz, and 8100Hz is input.

[0069] The preset frequency sound wave is input from one end of the air waveguide (1) according to the preset transmission rules. The time domain response of the sound pressure signal is detected from the detection end of each preset frequency sound wave, and the corresponding sound pressure amplitude information is output.

[0070] The detected sound pressure level information is converted into six target three-bit binary numbers.

[0071] To further verify the demodulator's ability to separate real-time mixing signals, a time-domain finite element simulation was performed in this embodiment. The device was excited using a time-varying signal. The mixing acoustic signal was input from the left entrance of the air waveguide 1 of the convoluted structure-based mixing acoustic demodulator. The signal consisted of six different frequency components (4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz, and 9700Hz), each independently carrying three bits of binary information ('1' indicates the presence of the frequency component, '0' indicates its absence), namely 001, 010, 011, 100, 101, and 110.

[0072] The time-domain response of the sound pressure signal at the bottom of the six curled channels is detected at the detection end of each preset frequency sound wave. Figure 5 The output waveforms of the six channels are shown under a set of mixed signals as input. It can be clearly observed that only the channel whose resonant frequency matches the frequency component of the input signal produces a significantly high amplitude response, and its waveform is consistent with the input pulse wave; while the output amplitudes of the other channels are close to the background noise level.

[0073] Most importantly, this demodulation process is completed instantaneously by a passive physical structure. A three-second mixing pulse signal is continuously input, and the input mixing sound is switched every second according to a preset rule, such as... Figure 5As shown, once the input pulse signal arrives at the receiver, the responses of each channel are generated synchronously with almost no delay, and the timing of their output signals is perfectly aligned with the input pulse. This indicates that the separation and information extraction of the mixed signal do not rely on any subsequent digital signal processing algorithms, but rather originate from the inherent physical interaction between the sound wave and the metamaterial structure. The working mechanism of the entire system can be summarized as "structure as demodulator"—sound waves of a specific frequency are captured and their energy localized by the corresponding resonant channel, directly mapping the frequency information into spatial location information and energy amplitude information at the physical level, which can then be directly read by a single sensor.

[0074] Because the input mixed acoustic signal contains the resonant frequencies of these channels, the detected signal exhibits significant enhancement and amplitude changes depending on the content of the incident acoustic wave. Therefore, by detecting the amplitude of the signals received in different channels, the frequency components and signal content of the input mixed acoustic signal can be clearly estimated.

[0075] To further highlight the unique advantages of the coil-structure-based mixer demodulator in parallel information transmission, this embodiment designs an image information transmission experiment to verify the use of the coil-structure-based mixer demodulator in image information transmission: directly transmitting and reconstructing simple image information using sound waves. The characters "N" and "J" are selected as the transmission objects, and the two image information are decomposed into a 3×3 binary pixel grid, where "1" represents a colored pixel and "0" represents a colorless pixel.

[0076] Each binary pixel grid is converted into three binary sequences: the character “N” is encoded as: first row “101”, second row “111”, third row “101”; the character “J” is encoded as: first row “111”, second row “010”, third row “110”.

[0077] The core function of the mixer demodulator based on the coiled structure in this embodiment lies in the fact that its six physical channels naturally form a parallel "acoustic data bus". The three rows of pixel information of N and J correspond to the acoustic channels formed by the three coiled structures 3 on both sides of the air wave vector 1, and are transmitted simultaneously through frequency division multiplexing. The transmission of the entire image is completed serially through three sets of continuous time-domain pulse signals.

[0078] Figure 6 The above sub-diagram illustrates the encoding and transmission process described above. Figure 6 The subplot below records the output response at the bottom of the six demodulation channels.

[0079] The simulation results are clear and accurate: the output pulses of the six channels perfectly reproduce the input pixel-coded sequence. For example... Figure 6As shown in the diagram above, when transmitting "N", channel six outputs a high pulse ('1') in the first second, a low level ('0') in the second second, and a high pulse ('1') in the third second, which is completely consistent with the preset "101". Similarly, channel three maintains a high level throughout when transmitting the first line of "J", accurately reproducing "111". This result strongly proves that the demodulator based on the coiled structure can serve as a highly efficient "acoustic information splitter". The mixer demodulator based on the coiled structure in this embodiment spatially demultiplexes the serially input mixer acoustic signal into multiple independent digital signal streams and outputs them directly in a physical manner. The entire demodulation process is completely passive and instantaneous, and requires no analog-to-digital conversion or digital signal processing operations, realizing end-to-end physical layer resolution from sound waves to digital information. The finite element simulation successfully verifies the feasibility of this design in implementing a simple, low-power acoustic communication system with high real-time requirements.

[0080] To provide higher resolution image information transmission for the characters "N" and "J", such as Figure 7 (b) Encode the characters “N” and “J” into a 6×6 binary pixel matrix, where “1” represents a colored pixel and “0” represents a colorless pixel. Based on the information transmission target, select six frequencies of sound waves (4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz, and 9700Hz) to form a mixed sound, transmitting two rows and six columns of image information respectively. The characters “N” and “J” are encoded into three binary sequences respectively; following the encoding rules from top to bottom and left to right, the specific encoding is as follows:

[0081] The character "N" corresponds to three binary sequences: "110011111011", "111111111111", and "110111110011".

[0082] The character "J" corresponds to three binary sequences: "111111111111", "000110100110", and "111110011100".

[0083] Figure 7 (a) illustrates the above encoding and transmission process. Figure 7 (b) records the output response at the bottom of the six demodulation channels. Figure 7 Simulation results in (a) show that the output pulses of the six channels accurately reproduce the input binary encoded sequence. Taking the red 4700Hz sound wave channel six as an example, it outputs a high level ('11') in the first second, a low level ('00') in the second second, and '11', '11', '10', and '11' in the third to sixth seconds respectively, which is completely consistent with the preset sequence "110011111011". The other channels also show the same accuracy.

[0084] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. A mixer-demodulator based on a coiled structure, characterized in that, Mixed sound for mixing multiple preset frequency sound waves is separated according to their respective frequencies, including: an air waveguide (1) for transmitting sound waves, an obstruction structure (2) set on both sides of the air waveguide (1) to block the sound waves from penetrating, and multiple coiled structures (3) for capturing the corresponding preset frequency sound waves. At least one of the blocking structures (2) of the air waveguide (1) is provided with a coiled structure (3) at intervals. The coiled structure (3) is open at one end near the air waveguide (1) and closed at the other end away from the air waveguide (1). Each coiled structure (3) has multiple crossbeams (4) built in to block the penetration of sound waves, which divide the internal channel of each coiled structure (3) into different lengths as different acoustic resonant cavities to capture sound waves of different frequencies. The closed end of each coiled structure (3) is the detection end of the sound wave of each preset frequency.

2. The mixer / demodulator based on a coiled structure according to claim 1, characterized in that, The internal channel lengths of the multiple curled structures (3) that capture the corresponding preset frequency sound waves are each one-quarter of the wavelength of the corresponding preset frequency sound waves. The minimum frequency interval between the preset frequency sound waves is greater than 5 times the bandwidth of each curled structure (3); The bandwidth of the coiled structure (3) is drawn by making a horizontal line 3dB downward from the peak of the resonant cavity frequency response curve, which intersects the curve at two points f1 and f2, where f1 < f2, and the bandwidth Δf = f2 - f1.

3. The mixer / demodulator based on a coiled structure according to claim 1, characterized in that, The spacing of the curled structure (3) is set according to the lowest preset frequency in the mixed sound to meet the preset sound insulation amount.

4. The mixer / demodulator based on a coiled structure according to claim 1, characterized in that, When the width of the internal channels of each coil structure (3) is the same and the size of each crossbeam (4) is the same, each coil structure (3) is set in order of high and low according to the preset frequency of the captured sound wave; When the blocking structures (2) on both sides of the air waveguide (1) are respectively provided with the curled structures (3), the curled structures (3) on one side of the air waveguide (1) are set in the forward order of the preset frequency of the captured sound waves, and the curled structures (3) on the other side of the air waveguide (1) are set in the reverse order of the preset frequency of the captured sound waves.

5. The mixer / demodulator based on a coiled structure according to claim 4, characterized in that, When the blocking structures (2) on both sides of the air waveguide (1) are respectively provided with the curled structure (3), the boundaries of the blocking structures (2) on both sides adjacent to the air waveguide (1) are parallel and the spacing distance is greater than one-quarter of the wavelength of the lowest preset frequency sound wave in the mixing sound.

6. The mixer / demodulator based on a coiled structure according to claim 4, characterized in that, When the mixed sound of the six preset frequency sound waves, which are sequentially decreasing in frequency, is separated according to their respective frequencies, a coiled structure (3) is provided in the blocking structure (2) on both sides of the air waveguide (1). A coiled structure (3) for capturing the first frequency sound wave, a coiled structure (3) for capturing the second frequency sound wave, and a coiled structure (3) for capturing the third frequency sound wave are sequentially arranged in the blocking structure (2) on one side of the air waveguide (1). The air waveguide (1) has a coiled structure (3) for capturing the sixth frequency sound wave, a coiled structure (3) for capturing the fifth frequency sound wave, and a coiled structure (3) for capturing the fourth frequency sound wave in sequence inside the barrier structure (2) on the other side.

7. The mixer / demodulator based on a coiled structure according to claim 1, characterized in that, When the mixed sound of six preset frequency sound waves (4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz and 9700Hz) is separated according to its respective frequency, the internal channel lengths of the curled structure (3) corresponding to the preset frequencies of 4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz and 9700Hz are 18.245mm, 15.044mm, 14.057mm, 12.25mm and 10mm respectively. 0.586mm and 8.84mm; The blocking structures (2) on both sides of the air waveguide (1) are respectively provided with a curled structure (3). The two blocking structures (2) are parallel to the boundary of the air waveguide (1) and the interval distance is 2.67mm. The interval distance of the curled structures (3) is 3mm. The curled structure (3) is a rectangular structure with a width of 0.375mm. The width of the channel inside the curled structure (3) is 0.025mm. The width of the crossbeam (4) is 0.025mm and the length is 0.35mm.

8. A method for using a mixer demodulator based on a coiled structure, characterized in that, Information transmission using the mixer demodulator based on the coiled structure as described in claim 1 includes: Select the preset frequencies that make up the mixing sound according to the information transmission target and preset the corresponding transmission rules; The preset frequency sound wave is input from one end of the air waveguide (1) according to the preset transmission rules, and is detected from the detection end of the preset frequency sound wave through each curled structure (3), and the corresponding sound pressure amplitude information is output. The detected sound pressure level information is converted into target information.

9. The method of using the mixer demodulator based on the coiled structure according to claim 8, characterized in that, The information transmission targets include binary sequences and image information based on binary sequences; When the information transmission target is a binary sequence, 1 indicates that there is a preset frequency sound wave, and 0 indicates that there is no preset frequency sound wave. The binary number is transmitted in sequence until the binary sequence transmission is completed. When the information transmission target is image information, the image information is converted into a binary pixel grid, where 1 represents a colored pixel and 0 represents a colorless pixel; the binary pixel grid is then converted into multiple binary sequences, and each binary sequence is transmitted separately.

10. The method of using the mixer demodulator based on the coiled structure according to claim 8, characterized in that, When using the frequency mixer demodulator based on a coiled structure as described in claim 6 or 7 for information transmission, and the information transmission target is one of the six three-bit binary numbers 001, 010, 011, 100, 101, and 110, Based on the information transmission target, sound waves of 4700Hz, 5700Hz, 6200Hz, 7000Hz, 8100Hz, and 9700Hz are selected to form a mixed sound, which is used to transmit 001, 010, 011, 100, 101, and 110 respectively. The transmission rules are as follows: in the first second, a mixed sound composed of sound waves of 7000Hz, 8100Hz, and 9700Hz is input; in the second second, a mixed sound composed of sound waves of 5700Hz, 6200Hz, and 9700Hz is input; and in the third second, a mixed sound composed of sound waves of 4700Hz, 6200Hz, and 8100Hz is input. The preset frequency sound wave is input from one end of the air waveguide (1) according to the preset transmission rules. The time domain response of the sound pressure signal is detected from the detection end of each preset frequency sound wave, and the corresponding sound pressure amplitude information is output. The detected sound pressure level information is converted into six target three-bit binary numbers.

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