CN114070408B - Method for designing acoustic communication waveform of ice-crossing medium - Google Patents
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Abstract
The invention discloses a method for designing acoustic communication waveforms across ice media, which comprises the steps of obtaining sea ice acoustic parameters, establishing a dispersion equation describing the characteristics of an ice layer elastic waveguide according to an elastic fluctuation theory, and solving the dispersion equation to obtain a phase velocity dispersion function c p According to c p Obtaining a group velocity dispersion function, and further obtaining a group velocity dispersion curve; determining sound source excitation parameters serving as a signal source, wherein the sound source excitation parameters comprise an excitation frequency range and an acoustic energy incidence angle range, and selecting a corresponding group velocity dispersion function in a dispersion curve according to the sound source excitation parameters; calculating a system transfer function according to the distance between the receiving end and the transmitting end based on the obtained frequency dispersion function; obtaining a system frequency domain response function based on the system transfer function and the expected pulse signal frequency domain waveform; and converting the frequency domain response function into a time domain, and inverting the time domain waveform to obtain a transmitting end waveform. The invention greatly increases the communication concealment while improving the communication distance and the communication reliability, and realizes the high-efficiency, stable and concealed ice-crossing fixed-point acoustic communication.
Description
Technical Field
The invention belongs to the technical field of polar region acoustics, and relates to a method for designing an acoustic communication waveform of a cross-ice medium.
Background
The arctic region is the focus of international social attention, serves as the basic guarantee of scientific cognition of the polar region and reasonable development and utilization of the polar region resources, the polar region equipment and technology are in urgent need of being supported by the global communication and perception capability integrated with sea, ice and heaven, and the arctic region is covered by the ice and snow layer throughout the year, so that the realization of a stable, remote and efficient ice medium-crossing communication technology is significant for forming polar region cross-domain perception and communication networks.
The basic technical route for acquiring the ice-crossing medium information comprises two major categories of equipment ice-crossing and energy ice-crossing, wherein the transmission of the ice-crossing medium information is realized by taking sound waves as a carrier, so that the problems of cost burden, construction risk, application environment limitation and the like brought by ice breaking and ice-penetrating deployment equipment can be avoided, and the method is an important potential means for realizing high-efficiency ice-crossing communication. The ice cover area of the North sea reaches hundreds to tens of millions of square kilometers, the average thickness is only 3-4 meters, and the macroscopic configuration of the thin plate causes the acoustic wave guide phenomenon of the ice layer: when the sound wave propagates in the ice, the wave is overlapped by interference, reflection and other phenomena at the upper and lower interfaces to form a traveling wave which stably propagates along the extending direction of the ice layer, namely a guided wave. The energy attenuation caused by spatial diffusion in the guided wave transmission process is obviously smaller than that of bulk waves, which is beneficial to long-distance sound propagation, but the complex sound propagation characteristic of the bulk waves brings challenges to the sound communication technology taking the bulk waves as carriers.
The widely applied coding technology in the field of underwater acoustic communication in the ice-free sea area is realized by transmitting pulse signals and controlling the transmission interval, and the communication distance and the communication reliability of the coding technology are highly dependent on the detection capability of the pulse signals and the accurate estimation of the arrival time of the pulse signals. When the technology is applied to polar sea areas to realize cross-ice medium acoustic communication, the multimode propagation and dispersion phenomenon brought by the ice layer acoustic waveguide causes the time domain broadening of acoustic energy, and the communication effect is seriously affected. On one hand, the time domain broadening of acoustic energy enables instantaneous and high-amplitude pulse signals to become long-trailing signals after long-range propagation, the detection difficulty of a receiving end is increased due to the reduction of the signal amplitude, and the communication concealment is seriously reduced and the information source transmitting end equipment is difficult to support due to the fact that the receiving signal amplitude can be improved due to the enhancement of the acoustic source energy; on the other hand, nonlinear time domain stretching increases signal arrival time judgment errors, and deteriorates communication efficiency.
Disclosure of Invention
Aiming at the prior art, the invention aims to provide the ice medium-crossing acoustic communication waveform design method based on the ice layer waveguide, so that the efficiency, stability and concealment of ice medium-crossing acoustic communication are improved.
In order to solve the technical problems, the invention relates to a method for designing an acoustic communication waveform of a cross-ice medium, which comprises the following steps:
step 1: acquiring sea ice sound parameters, establishing a dispersion characteristic equation describing the characteristics of the ice layer elastic waveguide according to an elastic fluctuation theory, and solving the dispersion characteristic equation to obtain a phase velocity dispersion function c of all modes of the ice layer acoustic waveguide in a target communication frequency band p And group velocity dispersion function c g ；
Step 2: determining sound source excitation parameters as information sources, including excitation frequency range and sound energy incidence angle range, and selecting group velocity dispersion function c corresponding to the mode with highest excitation efficiency according to the sound source excitation parameters g ′；
Step 3: based on the dispersion function c obtained in step 2 g ' calculating a system transfer function H (omega) according to the distance between the receiving end and the transmitting end;
step 4: obtaining a system frequency domain response function G (omega) based on the system transfer function H (omega) and the expected pulse signal frequency domain waveform in the step 3;
step 5: and converting the frequency domain response function G (omega) into a time domain, and inverting the time domain waveform to obtain a transmitting end waveform.
Further, in the step 1, the intermediate frequency equation is specifically:
wherein ,
in the formula ,ρ1 、c l 、c t The density, longitudinal wave velocity and transverse wave velocity of sea ice are respectively, h is the thickness of sea ice, ρ 2 C is the density of seawater and the wave velocity of longitudinal wave, k is the wave number of traveling wave, and p, q and r are coefficients related to the wave velocity and wave number, specifically:
further, in step 1, the group velocity dispersion function c g The method comprises the following steps:
c g ＝dω/dk
where ω is angular frequency, ω=k/c p 。
Further, in step 3, the system transfer function H (ω) is specifically:
wherein ,τg (omega) is the group delay,omega is angular frequency, d is propagation distance of guided wave, t 0 For the moment of excitation at the transmitting end, ψ H (0) The initial value is integrated for the phase frequency characteristic of H (omega).
Further, in step 4, the system frequency domain response function G (ω) is specifically:
G(ω)＝F(ω)H(ω)
where F (ω) is an excitation signal, and F (ω) is set as a pulse signal desired to be obtained at the receiving end.
The invention has the beneficial effects that: the invention provides a method for designing acoustic communication waveforms of a cross-ice medium, which changes the tradition that pulse signals are mostly and directly used as code element waveforms of a transmitting end in the existing method for acoustic communication of the cross-ice medium, calculates ice layer guided wave simulation signals through a system transfer function and expected pulse signal frequency domain waveforms, and performs time domain inversion on the ice layer guided wave simulation signals to complete the design of the waveforms of the transmitting end. And encoding the communication information into a designed transmitting waveform, and obtaining a pulse signal at an ice receiving end. Compared with the prior art, the method has the advantages that the preservation of acoustic signal energy along with propagation in the space dimension and the compression in the time dimension are realized through designing the code element waveform, the communication concealment is greatly improved while the communication distance and the communication reliability are improved, and the efficient, stable and concealed ice-crossing fixed-point acoustic communication is realized.
(1) And (3) improving the communication distance:
the maximum communication distance of a communication system is determined by the detectability of its receiving end to a given carrier signal, subject to signal amplitude under the same noise level and device detection capability conditions. When the existing ice-sound-crossing communication method mostly directly uses pulse signals as the code element waveforms of a transmitting end, on the basis of energy attenuation, the time domain broadening of the pulse signals caused by dispersion greatly reduces the signal amplitude, and the detectability of the ice-sound-crossing communication method is reduced. The method is characterized in that a transmitting signal waveform is designed based on the characteristic of the acoustic waveguide of the ice layer, the time domain widening process of the ice layer to the pulse signal is reversed, the pulsing of the ice layer at the receiving end is realized, the signal detectability of the receiving end is improved on the premise that the load power of the transmitting end is not increased, and the communication distance is expanded.
(2) Communication reliability is improved:
the common acoustic communication coding system takes the time delay of adjacent code element signals as an information carrier, and the communication reliability is highly correlated with the evaluation accuracy of the arrival time of carrier signals. The instantaneous excitation of the acoustic energy can be realized at the transmitting end by using the pulse signal, but under the action of the ice layer waveguide, the acoustic energy propagation speed of the broadband pulse signal changes along with the frequency, so that scattered arrival is formed at the receiving end. Therefore, this increases the estimation error of the signal arrival time, and affects the communication reliability, while making the energy detector-based signal recognition method difficult to apply. By redesigning the code element waveform, the acoustic signal energy is gradually compressed along with the propagation in the time dimension, so that the instantaneous arrival of the acoustic signal at the receiving end is realized, and the estimation accuracy and the communication reliability of the arrival time of the code element signal are improved.
(3) Increase communication concealment:
communication system concealment is represented by the possibility that communication behavior is found by non-target users, and is determined by signal detectability at a physical level, thus being closely related to signal amplitude intensity. When a pulse signal is directly used as an ice-crossing communication symbol, the signal amplitude monotonically decreases with increasing propagation distance under the dual influence of spatial diffusion and time domain broadening. Therefore, under the condition of the same detection capability, signals are easily intercepted by non-target users in the propagation process, and the dual requirements of long-range propagation and hidden communication are difficult to be met. When the code element waveform designed based on the ice layer waveguide characteristic is used, the convergence of acoustic energy corresponding to different frequencies at a designated distance from a receiving end is realized by reversely utilizing the time domain widening process of signals, so that the radiation power of a transmitting end can be reduced on the premise of ensuring the signal detectability of the receiving end, more targeted acoustic signal transmission is realized, and the communication concealment is improved.
Drawings
FIG. 1 is a schematic diagram of a scenario in which cross-icing acoustic communications are implemented in an embodiment of the present invention;
FIG. 2 is a flow chart of a waveform design method based on an ice layer waveguide in an embodiment of the invention;
FIG. 3 is a schematic diagram of a waveform design method based on an ice layer waveguide in an embodiment of the present invention;
FIG. 4 is a graph showing the group velocity dispersion of a sheet-like ice layer in an embodiment of the present invention;
FIG. 5 is a schematic diagram of time delay difference encoding based on a manual source in an embodiment of the invention;
FIG. 6 is a graph showing the dispersion of the phase velocity of a free steel plate model according to an embodiment of the present invention;
FIG. 7 is a waveform diagram of emissions based on a free steel plate model design in an embodiment of the present invention;
FIG. 8 is a waveform diagram of a free steel plate model receiving end in an embodiment of the invention.
Detailed Description
The invention is further described below with reference to the drawings and specific examples.
The invention relates to a method for designing acoustic communication waveforms of a cross-ice medium, which utilizes a polar ice layer as a main propagation medium to construct a stable cross-ice acoustic communication channel, wherein a communication scene is shown as a figure 1, the reciprocity of acoustic propagation of the ice layer channel is fully utilized, and by designing a signal waveform of a transmitting end, the time domain widening process of a pulse signal caused by dispersion is reversed, so that the pulsing of the acoustic signal at a receiving end is realized, and the invention is specifically as follows in combination with figures 2 and 3:
step 1: sea ice acoustic parameters (thickness, density and sound velocity) are obtained, a dispersion characteristic equation describing the characteristics of the ice layer elastic waveguide is established according to an elastic fluctuation theory, and the dispersion characteristic equation is solved to obtain phase velocity and group velocity dispersion function c of all modes of the ice layer acoustic waveguide in a target communication frequency band p And c g ；
The dispersion characteristic equation determines that the ice layer guided wave is multi-modal and dispersive, namely the relationship between the phase velocity, the group velocity and the frequency of the guided wave along the propagation direction is not linear, and the nonlinear relationship between different modes is different and is expressed as a phase velocity and group velocity dispersion curve.
Step 2: determining sound source excitation parameters as information sources, including excitation frequency range and sound energy incidence angle range, and selecting group velocity dispersion function c corresponding to efficient excitation mode according to the sound source excitation parameters g ′；
Wherein the system dispersion function is determined by a dispersion curve, which can be expressed as a function of modal velocity as a function of frequency. From the signal angle, the dispersion function can be understood as a phenomenon that different frequency components generate different time delays after a certain excitation signal passes through the transmission system. And selecting proper sound source excitation parameters, defining an excitation frequency range and an acoustic energy incidence angle range, and determining a corresponding dispersion function based on a dispersion curve conforming to the preset condition.
Step 3: calculating a system transfer function by counting the distance between the receiving end and the transmitting end based on the frequency dispersion function obtained in the step 2;
wherein the ice layer guided wave dispersion system transfer function is a function of the group delay between the transmitted signal and the received signal. Based on the dispersion function, the distance between the receiving end and the transmitting end is introduced, so that the group delay between the transmitting end and the receiving end can be calculated, and the system transfer function can be obtained. Which may be used to characterize the communication channel, establishing a connection between the output and input of the communication system. The transfer function is known, i.e. the output can be found from the input, or the input can be determined from the desired output.
Step 4: acquiring a system frequency domain response function based on the system transfer function and the expected pulse signal frequency domain waveform in the step 3;
the system frequency domain response function can be obtained by multiplying the system transfer function obtained in the step 3 and the expected pulse signal frequency domain waveform. Which is used to represent the response of the ice layer guided wave system to the input pulse signal.
Step 5: the frequency domain response is converted into the time domain, and the time domain waveform is inverted to complete the design of the transmitting end waveform.
The designed transmitting signal waveform is an ice layer guided wave dispersion signal. Different from the existing ice-sound-crossing communication method which mostly uses pulse signals as the code element waveforms of the transmitting end, the method converts the frequency domain response function of the system into time domain to obtain time domain dispersion carrier waves, and inverts the time domain to complete the design of the waveforms of the transmitting end. The design is based on the reciprocity of acoustic propagation of the ice layer communication channel. Because the acoustic propagation process in the ideal ice layer waveguide is reversible, the acoustic signal propagation after the input of the designed time reversal dispersion waveform can be understood as the inverse process of the dispersion process, and the channel output is a pulse signal. The process can realize energy conservation of signals in the space dimension and energy compression of signals in the time dimension, complete conversion from common receiving end dispersion tailing signals to pulse signals, increase the amplitude of the received signals, and therefore improve communication distance and communication reliability and communication concealment.
Examples are given below in connection with specific parameters:
embodiment one:
step 1: based on sea ice sound parameters (thickness, density and sound velocity), a corresponding ice layer sound waveguide theoretical model is established by combining an elastic fluctuation theory, and a dispersion equation is solved to obtain a group velocity dispersion curve.
The ice layer acoustic waveguide dispersion curve is obtained by solving a dispersion equation describing the fluctuation characteristics of the ice layer elastic guided wave, and the floating ice waveguide dispersion equation is as follows, and is related to sea ice acoustic parameters (thickness, density and sound velocity):
wherein ,
in the formula ,ρ1 、c l 、c t The density, longitudinal wave velocity and transverse wave velocity of sea ice are respectively, h is the thickness of sea ice, ρ 2 C is the density of seawater, the longitudinal wave velocity, k is the wave number of travelling wave, c p For phase velocity, p, q, r are all coefficients related to wave velocity and wave number, i.e
When p=0 and q=0, the above equations correspond to symmetric and antisymmetric modal dispersion equations, respectively, for a sheet in vacuum, as compared to the free sheet characteristic equation given by Lamb.
The dispersion equation determines that the guided wave of the ice layer is multi-modal and dispersive, namely the relationship between the phase velocity of the guided wave along the propagation direction and the frequency is not linear, and the nonlinear relationship between different modes is different and is expressed as a phase velocity dispersion curve. The group velocity is the velocity of the propagation of acoustic energy, and the group velocity dispersion curve can be obtained by calculating the relationship between the phase velocity and the group velocity.
Since the average sea depth in arctic regions is about 1200 m, the thickness of sea ice in large area observed in recent years is more than 2m, the difference between the sea ice and the ice is about three orders of magnitude, and the area of sea area reaches kilometer level, the sea depth and the area of sea area can be both approximate to infinity, and the thickness of ice layer is 1m and the density is 917kg/m 3 The longitudinal wave velocity is 3300m/s and the transverse wave velocity is 1913m/s. It is noted that the sea ice thickness and the sound velocity in the ice both appear with the change of seasons and air temperatureThe parameters need to be corrected for the environmental information during the actual application process because of the large variation.
On the premise that the information source meets the limited amplitude wave and the channel information is kept unchanged, the elastic wave propagation process has reciprocity, namely, the waveform is unchanged under the condition that the transmitting position and the receiving position are exchanged under the condition that the signal of the transmitting source is unchanged. Establishing an elastic wave propagation dispersion equation and passing through c g ＝dω/dk 0 The group velocity is calculated and the thin-plate ice layer group velocity dispersion curve is obtained as shown in figure 4.
Step 2, 3: and selecting a sound source excitation parameter (an excitation frequency range and an incidence angle range) as a source, determining a frequency dispersion function based on a frequency dispersion curve, and calculating a transfer function of the system by taking into account the distance between a receiving end and a transmitting end.
From the signal point of view, the dispersion function can be understood as a phenomenon that different frequency components generate different time delays after a certain excitation signal passes through the transmission system. Selecting a sound source excitation parameter as a source, determining an excitation frequency range and an acoustic energy incidence angle range, and determining a specific dispersion function c based on a dispersion curve g (omega) group delays between the transmitted and received signals of different frequencies can be calculated from the group velocity dispersion curve. I.e.
wherein ,t0 And d is the propagation distance of the guided wave at the moment of excitation of the transmitting end.
Assuming that the propagation attenuation in the ice layer is not considered, that is, the mode of H (ω) is constant 1, the transfer function of the ice layer waveguide dispersion system is H (ω), and there are:
wherein ψH (0) The initial value is integrated for the phase frequency characteristic of H (omega). Group delay τ g And (omega) is substituted into the above formula to obtain a transfer function H (omega).
Step 4: acquiring a system frequency domain response function based on the system transfer function and the expected pulse signal frequency domain waveform in the step 3;
setting the excitation signal as F (omega), the frequency spectrum of the receiving signal as G (omega), setting the excitation signal as F (omega) as a pulse signal expected to be obtained at the receiving end, and multiplying the pulse signal by a system transfer function H (omega) to obtain a theoretical output dispersion signal G (omega) of the ice layer waveguide dispersion system, namely
G(ω)＝F(ω)H(ω)
Step 5: the frequency domain response is converted into the time domain, and the time domain waveform is inverted to complete the design of the transmitting end waveform.
And converting the time domain dispersion waveform into a time domain to obtain a corresponding ice layer guided wave simulation dispersion signal, and reversing the corresponding ice layer guided wave simulation dispersion signal in the time domain to complete the design of the waveform of the transmitting end. And writing the target communication information into a carrier signal by taking the designed transmitting waveform as an information carrier through modes of delay difference coding, differential delay difference coding and the like. Taking delay difference encoding as an example, the instruction information transmitted by each symbol is modulated in the delay value of the dispersive signal in the symbol window, and the width of each symbol window is fixed. τ in FIG. 5 i (i=1, 2,3, …) represents the delay value of the pulse code at each symbol window; t (T) P The time width of the pulse code; the width of each symbol is fixed to T 0 ＝T P +T c ，T c Is the encoding time. If the information carried by each code element is nbit, the coding time T is obtained c Is equally divided into (2) n -1) parts, Δτ=t c /(2 n -1) for the coding quantization interval, then there are:
τ i ＝k i Δτ，k＝0,1，...，2 n -1
in the above, τ i The value of (2) determines the information it represents, assuming n=4, if k=0, then represents information "0000", the position of the pulse code is τ=0; if k=4, the information "0100" is represented, and the position of the pulse code in the symbol window is τ=4Δτ. The communication rate of the system is as follows:
then selecting a manual point source to excite the coded signal under water. Because the acoustic propagation process in the ideal ice layer waveguide is reversible, the acoustic signal propagation after the designed time reversal dispersion waveform is input can be understood as the inverse process of the dispersion process, and the theoretical transfer function can be understood as the inverse system of the dispersion transfer function, namely:
the mode of H (ω) is set to be constant 1, so that the amplitude of each frequency component is kept constant before and after the waveform design.
And finally, decoding the pulse signal obtained by the ice receiving end to obtain the communication information. The process can realize energy conservation of signals in the space dimension and energy compression of signals in the time dimension, complete conversion from common receiving end dispersion tailing signals to pulse signals, improve the detectability of the signals and the accuracy of time-in judgment, and further improve the communication distance and the communication reliability of the system. When the code element waveform designed based on the ice layer waveguide characteristic is used, the convergence of acoustic energy corresponding to different frequencies at a receiving end is realized by reversely utilizing the time domain widening process of signals, so that the signal amplitude of a transmitting end can be reduced on the premise of ensuring the signal detectability of the receiving end, the communication concealment is improved, and the high-efficiency, stable and concealed ice-crossing medium acoustic communication is realized.
In order to further verify the feasibility of the ice layer waveguide-based cross-ice acoustic communication waveform design method, a COMSOL numerical simulation method is utilized to construct a free steel plate model, a transmitting waveform is designed based on reciprocity of communication channel acoustic propagation, and the pulsing effect of acoustic signals is observed at a receiving end.
The steel plate had a thickness of 0.2m and a density of 7855kg/m 3 And constructing an acoustic model of the infinite-length free steel plate, wherein the longitudinal wave speed is 5943m/s, the transverse wave speed is 3238 m/s. And establishing an elastic wave propagation dispersion equation based on the model, solving to obtain a steel plate phase velocity dispersion curve as shown in fig. 6, and realizing modal separation. Bending waves, compared to other guided wave modesIn the propagation process, the energy amplitude is higher and is easier to be detected at the receiving end, but the frequency of a common transmitting signal for the ice-sound communication is 1-2kHz, and as can be known from fig. 6, the bending wave mode in the steel plate structure has serious dispersion in the frequency band, and the communication reliability and the communication distance are influenced. Therefore, the emission waveform is redesigned based on the bending wave of the low frequency band (1-3 kHz) so as to avoid the defect caused by the dispersion phenomenon.
According to the technical scheme, the transmitting waveforms are designed according to the steps 2 to 5, as shown in fig. 7, and are input into a steel plate acoustic propagation model, and waveforms are obtained at a receiving end, as shown in fig. 8. Therefore, the dispersion phenomenon is basically eliminated, the pulsing of the signal at the receiving end is realized, the energy amplitude of the signal is not reduced and increased under the influence of energy attenuation caused by space diffusion in the transmission process, the space energy of the low dimension of the steel plate waveguide is more fully exerted, and the communication distance is improved. In addition, the code element waveform enables the acoustic signal energy to be gradually compressed along with the propagation in the time dimension, so that the instantaneous arrival of the acoustic signal at the receiving end is realized, and the estimation accuracy and the communication reliability of the arrival time of the code element signal are expected to be improved. Further, by applying the method, the amplitude of the signal of the transmitting end can be reduced on the premise of ensuring the detectability of the signal of the receiving end, so that the communication concealment is improved.
Therefore, the waveform design method has the advantages that the improvement effect of the acoustic communication quality in the elastic medium is verified, and the waveform design method is also effective in the application to the cross-ice medium acoustic communication based on the ice layer acoustic waveguide.
Claims (3)
1. The method for designing the acoustic communication waveform of the ice medium is characterized by comprising the following steps of:
step 1: acquiring sea ice sound parameters, establishing a dispersion characteristic equation describing the characteristics of the ice layer elastic waveguide according to an elastic fluctuation theory, and solving the dispersion characteristic equation to obtain a phase velocity dispersion function c of all modes of the ice layer acoustic waveguide in a target communication frequency band p And group velocity dispersion function c g ；
Step 2: determining sound source excitation parameters as information sources, including excitation frequency range and acoustic energy incidence angle range, and selecting the mode with highest excitation efficiency according to the sound source excitation parametersGroup velocity dispersion function c of (2) g ′；
Step 3: based on the dispersion function c obtained in step 2 g ' calculating a system transfer function H (omega) according to the distance between the receiving end and the transmitting end;
step 4: obtaining a system frequency domain response function G (omega) based on the system transfer function H (omega) and the expected pulse signal frequency domain waveform in the step 3;
step 5: converting the frequency domain response function G (omega) into a time domain, and inverting the time domain waveform to obtain a transmitting end waveform;
the dispersion characteristic equation in the step 1 is specifically:
wherein ,
in the formula ,ρ1 、c l 、c t The density, longitudinal wave velocity and transverse wave velocity of sea ice are respectively, h is the thickness of sea ice, ρ 2 C is the density of seawater and the wave velocity of longitudinal wave, k is the wave number of traveling wave, and p, q and r are coefficients related to the wave velocity and wave number, specifically:
the system transfer function H (ω) in step 3 is specifically:
wherein ,τg (omega) is the group delay,omega is angular frequency, d is propagation distance of guided wave, t 0 For the moment of excitation at the transmitting end, ψ H (0) The initial value is integrated for the phase frequency characteristic of H (omega).
2. The method for designing an acoustic communication waveform across ice media according to claim 1, wherein: step 1, group velocity dispersion function c g The method comprises the following steps:
c g ＝dω/dk
where ω is angular frequency, ω=k/c p 。
3. The method for designing an acoustic communication waveform across ice media according to claim 1, wherein: the system frequency domain response function G (ω) in step 4 specifically includes:
G(ω)＝F(ω)H(ω)
where F (ω) is an excitation signal, set to a pulse signal desired to be obtained at the receiving end.
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
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| CN108777598A (en) * | 2018-07-31 | 2018-11-09 | 哈尔滨工程大学 | A kind of quarice layer medium communication method |
| CN111077532A (en) * | 2019-11-22 | 2020-04-28 | 同济大学 | Surface feature space information acquisition method based on deconvolution and Gaussian decomposition |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2004015762A (en) * | 2002-06-11 | 2004-01-15 | Nec Corp | Underwater communication system |
| CN106019288A (en) * | 2016-06-17 | 2016-10-12 | 西北工业大学 | Normal wave modal frequency dispersion elimination transformation-based sound source distance and depth estimation method |
| CN108777598A (en) * | 2018-07-31 | 2018-11-09 | 哈尔滨工程大学 | A kind of quarice layer medium communication method |
| CN111077532A (en) * | 2019-11-22 | 2020-04-28 | 同济大学 | Surface feature space information acquisition method based on deconvolution and Gaussian decomposition |
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