Sonar detection and communication integrated system based on OFDM-LFM signal

Abstract

The invention discloses a sonar detection and communication integrated system based on an OFDM-LFM signal, and relates to the technical field of underwater information, and the sonar detection and communication integrated system comprises a transmitting transducer array which is used for transmitting an OFDM-LFM integrated signal; the receiving hydrophone array is used for receiving a target echo signal and a communication signal; and the electronic bin is used for generating an OFDM-LFM integrated signal and processing the signal. According to the invention, active sonar target detection and parameter (distance, speed and the like) estimation are realized by adopting a multi-carrier communication waveform, and a sonar detection function is realized under the condition that the research does not influence the communication information transmission performance under the existing mature underwater acoustic communication system, so that the purpose of integration of detection and communication is achieved, the size of a platform is reduced, the power consumption is reduced, and the concealment is enhanced.

Description

Technical Field

[0001] The present invention relates to the field of underwater information technology, and particularly to a sonar detection and communication integrated system based on OFDM-LFM signals. Background Art

[0002] The integrated detection and communication technology can significantly reduce the system cost, improve the energy efficiency and spectrum utilization rate by sharing waveform, hardware and spectrum resources, and effectively alleviate the problem of scarce spectrum resources. The early research of this technology focused on the integration of radar and communication. For example, in the 1960s, Mealey proposed a one-way communication system based on radar pulse modulation, and the feasibility of radar-communication integration was verified by subsequent experiments. However, the integrated underwater detection and communication technology is still in the exploratory stage due to the inherent complexity of the underwater acoustic channel (including multipath interference, Doppler effect, channel time-variation, etc.), and the existing research results are limited. In the prior art, Northwestern Polytechnical University and Harbin Engineering University have respectively conducted preliminary research on underwater acoustic communication modulation methods and sonar array design, but a systematic solution has not been formed yet.

[0003] The current integrated underwater detection and communication systems are mainly divided into four categories: time-division, frequency-division, beam-division and full-sharing. The time-division, frequency-division and beam-division systems achieve function multiplexing through the separation of time-domain, frequency-domain or space-domain resources. Their implementation is simple and does not require significant adjustment of waveforms and hardware, but there are problems such as low utilization rate of time-frequency-space domain resources and difficulty in meeting the integrity requirements of detection and communication performance. Although the full-sharing system realizes deep resource sharing through collaborative design, it needs to divide signal types (based on communication or detection signals) according to the primary and secondary functions, and its practical application is limited by the characteristics of the underwater acoustic channel and the complexity of signal processing.

[0004] In the existing underwater information systems, active sonar detection and underwater acoustic communication devices are mostly independently designed, resulting in a large system volume, high power consumption and insufficient spectrum resource utilization rate, and it is difficult to meet the requirements of underwater combat platforms for concealment, energy efficiency and spectrum efficiency. In addition, the significant differences between the underwater acoustic channel and the electromagnetic channel make it impossible to directly transplant traditional radar-communication integration methods to underwater scenarios. Therefore, there is an urgent need for an underwater detection and communication integrated technology solution suitable for complex underwater acoustic environments that can balance detection performance and communication reliability. Summary of the Invention

[0005] In view of the problems of the existing underwater detection and communication systems being designed and used separately, with large volume occupation and high power consumption, referring to the integrated radar communication technology, and according to the characteristics of underwater detection and communication, the present invention proposes an integrated sonar detection and communication system based on OFDM-LFM signals, studies the implementation method of integrated detection and communication of an active sonar system, as well as the integrated waveform design suitable for the underwater acoustic environment, uses a multi-carrier communication waveform to realize the detection of active sonar targets and the estimation of parameters (such as distance, speed, etc.), and under the existing mature underwater acoustic communication system, studies the realization of sonar detection function without affecting the communication information transmission performance, so as to achieve the purpose of integrated detection and communication, reduce the volume of the platform, lower the power consumption, and enhance the concealment.

[0006] The technical solution of the present invention is as follows:

[0007] An integrated sonar detection and communication system based on OFDM-LFM signals, comprising:

[0008] A transmitting transducer array for transmitting OFDM-LFM integrated signals;

[0009] A receiving hydrophone array for receiving target echo signals and communication signals;

[0010] An electronic cabin for generating OFDM-LFM integrated signals and signal processing.

[0011] Further, the electronic cabin includes a processing circuit for performing the following operations:

[0012] a. Under the OFDM multi-carrier communication system, divide the frequency domain into multiple mutually orthogonal sub-channels, and allocate non-overlapping sub-carrier sets for the detection function and the communication function;

[0013] b. Adopt the OFDM interleaved sub-carrier allocation method to allocate sub-carrier resources to the detection function and the communication function;

[0014] c. Enable the communication data to generate OFDM-LFM integrated signals through joint transmit beamforming;

[0015] d. Demodulate the received target echo signals and communication signals to realize the target detection function and obtain the communication data.

[0016] Further, the transmitting transducer array adopts a 1x4 linear array method, consists of 4 array elements, the element spacing is half a wavelength, and is fixed by a bracket and integrated with the electronic cabin as a whole.

[0017] Further, the receiving hydrophone array adopts a 3x4 planar array method, consists of 12 array elements, the element spacing is half a wavelength, and is fixed by a bracket and integrated with the electronic cabin as a whole.

[0018] Furthermore, at the transmitting end, communication and detection resources and power are first allocated based on the channel prediction results to form a transmission signal matrix, and the signal is sent after inverse discrete Fourier transform, insertion of cyclic prefix, digital-to-analog conversion, and transmitting transducer array.

[0019] Furthermore, after receiving the signal, the communication user demodulates the signal on the communication resource block to obtain communication data.

[0020] Furthermore, after the transmitted signal is reflected by the target, the receiving end receives the echo signal and performs correlation processing on the received signal on the detection resource block with the original transmitted signal to realize the target detection function.

[0021] Furthermore, a portion of resources is optimally allocated for communication in each frame of multiple consecutive OFDM symbols, and the detection function consists of the concatenation of the remaining resources, wherein the energy budget is optimized in a subcarrier manner to ensure a high peak sidelobe ratio of the detection ambiguity function.

[0022] Furthermore, the transmitting transducer array and the receiving hydrophone array share a bracket.

[0023] Furthermore, the pulse repetition period in the detection is represented by the duration of an OFDM signal, and a plurality of consecutive OFDM symbols are combined to extend the coherent processing interval.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] Active sonar detection and underwater acoustic communication are indispensable underwater information technologies for surface and underwater combat platforms. The underwater detection and communication integration technology that combines underwater detection and communication has the advantages of reducing the platform size, reducing the overall power consumption of the platform, improving spectrum utilization and concealment, and can significantly improve the work efficiency of the entire system. The integration of underwater detection and communication can realize the sharing of multiple resources, improve the system's survivability and adaptability, and will become the development trend of future integrated electronic information systems. Therefore, the integration of underwater sonar detection and communication has far-reaching significance for the utilization and development of the ocean and marine national defense security. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the structure of a sonar detection and communication integrated system based on OFDM-LFM signal;

[0027] Figure 2 This is a schematic diagram of the layout of the transmitting transducer array;

[0028] Figure 3 This is a schematic diagram of the receiving hydrophone array layout;

[0029] Figure 4 It is a schematic diagram of the integrated resource sharing method;

[0030] Figure 5 Schematic diagram for the frequency-domain carrier allocation of a single OFDM symbol

[0031] Figure 6 Time-frequency relationship diagram of the OFDM-LFM signal for a single OFDM symbol

[0032] Figure 7 Integrated OFDM transmission waveform diagram

[0033] Figure 8 Integrated system architecture model

[0034] Figure 9 Joint transmission beam diagram of the integrated detection and communication system

[0035] Figure 10 Ambiguity function diagram

[0036] Figure 11 Bit error rate curve diagram Detailed implementation manners

[0037] It should be noted that relational terms such as "first" and "second" are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements not only includes those elements, but also includes other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "including a..." does not exclude the existence of additional identical elements in the process, method, article or device including the said element.

[0038] The features and performance of the present invention will be further described in detail below in conjunction with embodiments.

[0039] Embodiment 1

[0040] There is an overlap in the working frequency bands between detection and communication, and there are also similarities in the hardware structure and working principles. The complete detection and communication system has a similar structure in hardware such as the transmitting unit, receiving unit, and signal processor, making it possible to integrate underwater detection and communication.

[0041] In this embodiment, while maintaining the normal communication transmission performance, the target detection function is achieved. The resource allocation / waveform design is optimized in the time domain, frequency domain, and power domain to effectively integrate the OFDM-based communication and detection functions.

[0042] For a communication-centered design, to maximize the data transmission rate, first, a part of the subcarrier resources is allocated for communication based on the prior knowledge of the communication channel, and then the remaining subcarrier resources are used for detection. By optimizing its power allocation, the sidelobe level is suppressed to improve the detection performance.

[0043] In this embodiment, according to the integrated waveform design method of detection and communication under the full-sharing system, combined with the underwater environment, using OFDM subcarriers as the base signal, an integrated sonar detection and communication technology and system of OFDM-LFM signals suitable for underwater is proposed. By sharing a set of hardware devices, active sonar detection and communication transmission can be realized simultaneously. The two radio frequency systems share waveforms, hardware, spectrum, etc., which can reduce the overall cost of the system, improve energy efficiency and spectrum efficiency, and alleviate the problem of underwater spectrum scarcity and congestion. While maintaining normal target communication performance, the detection function is realized.

[0044] In this embodiment, specifically, an integrated sonar detection and communication system based on OFDM-LFM signals includes:

[0045] A transmitting transducer array for transmitting OFDM-LFM integrated signals;

[0046] A receiving hydrophone array for receiving target echo signals and communication signals;

[0047] An electronics cabin for generating OFDM-LFM integrated signals and signal processing; the transmitting transducer array, the receiving hydrophone array, and the electronics cabin are rigidly connected together to form an integral whole and are jointly deployed into the target water area.

[0048] In this embodiment, specifically, the electronics cabin includes a processing circuit for performing the following operations:

[0049] a. In the OFDM multi-carrier communication system, the frequency domain is divided into multiple mutually orthogonal sub-channels, and non-overlapping sub-carrier sets are allocated for the detection function and the communication function;

[0050] b. The sub-carrier resources are allocated to the detection function and the communication function by using the OFDM interleaved sub-carrier allocation method;

[0051] c. The communication data is used to generate OFDM-LFM integrated signals through joint transmit beamforming;

[0052] d. Demodulate the received target echo signals and communication signals to realize the target detection function and obtain communication data.

[0053] It should be noted that this system adopts a full-resource sharing method to realize the sharing of hardware platforms such as acoustic sensor arrays, receiving parts, transmitting parts, and processors. The integrated resource sharing method is as Figure 4As shown. This integrated resource sharing method realizes the full sharing of waveforms, information processing, functional algorithms, and information. The key to integration lies in integrated shared waveform design, joint transmit beamforming, joint signal reception and processing, etc.

[0054] At the transmitting end, operations such as signal design, beamforming, precoding, modulation, and power amplification are performed to overcome the interference between detection and communication and ensure that the performance indicators of both are not affected too much.

[0055] At the receiving end, the signals received by the hydrophone array may receive detection echoes and communication signals simultaneously. The detection echoes and communication signals are in the same frequency band, and they need to be separated and the interference signals need to be suppressed. At the detection receiving end, the detection signal processor needs to identify and suppress communication signals to accurately recover the target echo; at the communication receiving end, the communication signal processor needs to suppress the detection echo to demodulate the communication signal with a low bit error rate.

[0056] In this embodiment, specifically, the transmitting transducer array adopts a 1x4 linear array, which consists of 4 array elements. The element spacing is half a wavelength, and it is fixed by a bracket and forms an integral body with the electronic cabin. The design of this part of the linear array shares the array bracket with the receiving array. The layout schematic diagram of the transmitting transducer array is as Figure 2 shown.

[0057] In this embodiment, specifically, the receiving hydrophone array adopts a 3x4 planar array, which consists of 12 array elements. The element spacing is half a wavelength, and it is fixed by a bracket and forms an integral body with the electronic cabin. The design of this part of the planar array shares the array bracket with the transmitting array. The layout schematic diagram of the receiving hydrophone planar array is as Figure 3 shown.

[0058] In this embodiment, specifically, at the transmitting end, first, based on the channel prediction result, communication and detection resources and power are allocated to form a transmitted signal matrix. After inverse discrete Fourier transform, inserting a cyclic prefix, digital-to-analog conversion, and passing through the transmitting transducer array, the signal is transmitted.

[0059] In this embodiment, specifically, after the communication user receives the signal, the signal on the communication resource block is demodulated to obtain communication data.

[0060] In this embodiment, specifically, after the transmitted signal is reflected by the target, the receiving end receives the echo signal. The received signal on the detection resource block is correlated with the original transmitted signal to achieve the function of target detection.

[0061] In this embodiment, specifically, within each frame of multiple consecutive OFDM symbols, a part of the resources is optimally allocated for communication, and the detection function is composed of the concatenation of the remaining resources. Among them, the energy budget is optimized in the subcarrier manner to ensure the peak sidelobe ratio of the detection ambiguity function.

[0062] In this embodiment, specifically, the transmitting transducer array and the receiving hydrophone array share a bracket.

[0063] In this embodiment, specifically, the pulse repetition period in detection is represented by the duration of an OFDM signal, and multiple consecutive OFDM symbols are combined to extend the coherent processing interval.

[0064] In this embodiment, the shared waveform design includes:

[0065] Due to the different requirements of detection and communication functions, the integrated waveform design is crucial. For the detection function, waveforms with good autocorrelation characteristics are more suitable for sonar detection and positioning; for the communication function, communication symbols are often random and it is not easy to maintain good autocorrelation characteristics;

[0066] Currently, the underwater acoustic detection signal systems mainly include LFM linear frequency modulation and CW pulses, etc.; the underwater acoustic communication signal systems include spread spectrum, pulse position modulation, single carrier, multi-carrier, etc., combined with multi-system underwater acoustic communications such as PSK, FSK, MSK, frequency hopping, single sideband modulation, etc. The full sharing of sonar detection and communication integration needs to achieve the deep integration of sonar detection and underwater acoustic communication functions, and it is necessary to consider the performance of sonar detection and communication at the same time, and also optimize the design for the unique working mode of sonar;

[0067] OFDM signals have the advantages of high spectral efficiency and anti-multipath fading, etc., and are widely used in communication systems. Although the OFDM waveform is random, when a constant amplitude constellation diagram is applied, the OFDM waveform has good autocorrelation characteristics. Under this waveform design, OFDM only needs to make a small modification to the existing infrastructure and can have good detection performance;

[0068] In the OFDM multi-carrier communication system, the frequency domain is divided into multiple orthogonal sub-channels for use, and non-overlapping sub-carrier sets are allocated for detection and communication functions, and the orthogonality between sub-carriers is used to eliminate interference;

[0069] At the same time, the communication sub-carriers and the detection sub-carriers can be designed separately to meet different design requirements;

[0070] In the most common frequency selective fading channel in the wireless environment, there is often a strong correlation between the channel gains of adjacent sub-carriers. In order to avoid the situation where all sub-carriers are in deep fade caused by the detection or communication allocating consecutive sub-carriers, the OFDM interleaved sub-carrier allocation method is adopted, and the sub-carriers used for detection and communication functions are discontinuous, so that the situation where all sub-carriers are in deep fade can be avoided;

[0071] The schematic diagram of the frequency domain carrier allocation of a single OFDM symbol is asFigure 5 as shown;

[0072] In underwater acoustic communication, the undulating sea surface, changing ocean environment, and movement of ships and underwater vehicles will all cause Doppler frequency shift. Since the propagation speed of sound waves in water is relatively low, even a relatively small relative movement between the transmitter and receiver will cause a relatively serious Doppler frequency shift, resulting in spectral distortion of the received signal and seriously affecting the communication quality.

[0073] OFDM signals are very sensitive to Doppler frequency shift. To reduce this characteristic of OFDM signals, they can be combined with linear frequency modulation (LFM) signals. LFM signals have characteristics such as a large time-bandwidth product and strong anti-interference ability, and are widely used in detection and communication; OFDM signals have advantages such as high spectral utilization rate and anti-multipath fading, and are widely used in communication systems. The combination of OFDM-LFM technology can combine the advantages of both, improve the frequency band utilization rate, anti-multipath fading, and reduce the influence of Doppler frequency shift.

[0074] By modulating the LFM signal with OFDM, an OFDM-LFM waveform can be obtained. The mathematical expression of the frequency modulation waveform of OFDM-LFM can be expressed as:

[0075]

[0076] where t (0 ≤ t ≤ T) represents the time sample of the signal, N is the total number of subcarriers, u(t) (0 ≤ t ≤ T) is the rectangular window function, f n and k n represent the starting frequency and slope of the nth subcarrier of the signal s(t), respectively.

[0077] When the frequency modulation slopes of any two subcarriers are the same, their inner product can be expressed as:

[0078]

[0079] In the above formula, n = 1, 2,..., N; * is the conjugate. To make these two subcarriers orthogonal, it should be made So the frequency interval between subcarriers f n and is:

[0080]

[0081] where p is any integer.

[0082] The integrated signal model can be expressed as Figure 6As shown. The pulse repetition period in detection can be represented by the duration of an OFDM signal. To improve the velocity resolution in active sonar detection, multiple consecutive OFDM symbols can be combined to extend the coherent processing interval, such as Figure 7 shown.

[0083] In this embodiment, waveform design is centered around communication. While ensuring the best data rate, the detection performance is improved, and a part of the resources is optimally allocated for communication within each frame of multiple consecutive OFDM symbols.

[0084] Then, the detection function is composed of the remaining resources to ensure the peak sidelobe ratio of the detection ambiguity function.

[0085] In this embodiment, the joint transmit beamforming includes:

[0086] The OFDM integrated transmit waveform is used for target detection and communication data transmission. The system architecture model is as Figure 8 shown. At the transmit end, first, based on the channel prediction result, communication and detection resources and power are allocated to form a transmit signal matrix. After inverse discrete Fourier transform, inserting a cyclic prefix, digital-to-analog conversion, sonar transmit transducer array and other modules, the signal is transmitted.

[0087] After the communication user receives the signal, the signal on the communication resource block is demodulated to obtain communication data.

[0088] Meanwhile, after the transmit signal is reflected by the target, the receiving end receives the echo signal, and the received signal on the detection resource block is correlated with the original transmit signal to achieve the function of target detection.

[0089] To improve the detection performance while ensuring the best data rate, a part of the resources is optimally allocated for communication within each frame of multiple consecutive OFDM symbols. Then, the detection function is composed of the concatenation of the remaining resources, where the energy budget is optimized in a subcarrier manner to ensure the peak sidelobe ratio of the detection ambiguity function.

[0090] Each coherent processing interval for detection considers a frame of M consecutive OFDM symbols. Each frame has N subcarriers. The k-th subcarrier of the M-th symbol is called the (M,k) subcarrier resource. To avoid mutual interference between detection and communication, these two subsystems occupy different subcarrier resources in each frame. The matrix U(m,k) is used to represent the subcarriers selected for detection or communication,

[0091]

[0092] where U ∈ M×N.

[0093] such as Figure 2 and Figure 3The shown transmitting and receiving arrays consider a multi-antenna element OFDM system.

[0094] The integrated system consists of a transmitting transducer array (T X ) with 4 elements and a receiving hydrophone array (R X ) with 12 elements. When transmitting M OFDM symbols, each frame has K subcarriers, and the signal transmitted by the z-th antenna can be expressed as:

[0095]

[0096] where is the modulation symbol transmitted at the m-th OFDM symbol and the k-th subcarrier on the z-th transmitting element, g(t) is the pulse used, T s is the OFDM symbol duration, and Δf = 1 / t is the subcarrier spacing.

[0097] Let the number of transmitting elements in the system be N T , and the number of receiving elements be N R . The power of the OFDM signal to be transmitted is split between detection and communication, that is, part of the total available power is used for the detection function and part for the communication function. Therefore, the transmit beamforming vector W T can be expressed as:

[0098] W T = ω D W T,D + ω C W T,C

[0099] where ω D and ω C are the weighting coefficients for detection and communication respectively, ω D + ω C = 1, and W T,D and W T,C are the transmit beam vectors for detection and communication respectively.

[0100]

[0101] where is the gain of the transmitting element along the beam direction, is the effective isotropic radiated power, and are the steering vectors for detection and communication respectively. The element spacing of the present invention is half a wavelength, and the steering vector of the 1x4 linear array can be expressed as:

[0102]

[0103] The combined transmit beam pattern of the detection and communication integrated system is asFigure 9 as shown

[0104] The received signal of each array element antenna can be expressed as:

[0105]

[0106] In the formula, is the channel matrix of the m-th OFDM symbol and the k-th subcarrier, is the antenna self-interference vector, is the noise vector.

[0107] To further verify the performance of the system, the performance of a sonar detection and communication integrated system based on OFDM-LFM signals proposed in this embodiment is evaluated below.

[0108] When the total system power is constant, if the detection ability is to be ensured, the communication coverage range will decrease; if the communication coverage range is to be ensured, the detection range will decrease. The design of the detection waveform focuses on the time-delay Doppler domain, hoping to obtain a high main lobe to sidelobe ratio in the time-delay Doppler domain to improve the detection accuracy; the design of the communication waveform focuses on the time-frequency domain, hoping to utilize the subcarrier resources with good signal conditions as much as possible through reasonable power allocation to improve the transmission data rate.

[0109] In the integrated waveform design centered on communication, it is hoped to improve the main lobe to sidelobe ratio in the ambiguity function as much as possible under the premise of maximizing the achievable data rate. First, under the constraint of the given total communication power, optimize the communication power allocation to maximize the achievable communication data rate; second, set a channel threshold. When the channel gain corresponding to a certain subcarrier resource is greater than this value, it will be occupied by communication, and if it is less, it will not be occupied by communication. Therefore, these subcarrier resources not occupied by communication can be used for detection without affecting the communication performance, and all subcarrier resources are divided into communication subcarrier resources and detection subcarrier resources; finally, under the constraint of the given total detection power, optimize the detection power allocation matrix for the detection subcarrier resources to maximize the main lobe to sidelobe ratio in the ambiguity function.

[0110] Among the commonly used underwater modulation methods, FSK has low complexity, strong anti-interference ability, low frequency band utilization rate, and low channel requirements; MSK is strictly orthogonal, has a constant envelope, continuous phase, and little out-of-band power leakage; PSK has a high frequency band utilization rate and strong anti-interference ability. In this invention, the MSK modulation method is taken as an example to analyze the detection and communication performance of the detection and communication integrated system described in the invention.

[0111] The g-th symbol of the BPSK signal can be expressed as:

[0112] S BPSK (t) = cos(2πf ct + πd g )

[0113] Where f c is the carrier frequency, d g is the g-th communication symbol, and the integrated waveform formula obtained by combining OFDM-LFM technology is:

[0114]

[0115] Where N s is the number of symbols, N is the number of subcarriers, μ is the frequency modulation slope, T s is the symbol width, d m,n is the communication symbol modulated within the m-th OFDM symbol on the n-th subcarrier.

[0116] The detection ambiguity function is an important basis for evaluating the sonar detection performance. The ambiguity function of the signal s(t) can be expressed as:

[0117]

[0118] Where τ is the time delay, f d is the Doppler frequency shift, χ(τ, f d ) is the ambiguity function, * is the conjugate.

[0119] Assume that the signal carrier frequency is 8 kHz, the frequency band is 5 - 11 kHz, and the sampling frequency is 128 kHz. Simulate the MSK integrated signal based on the OFDM-LFM signal to obtain the ambiguity function graph and perform normalization processing on it, as Figure 11 shown. It can be seen from Figure 10 that the ambiguity function approximate graph of the MSK integrated signal based on the OFDM-LFM signal is approximately thumbtack-shaped, with good time and frequency resolution and low sidelobes, so it has good detection ability.

[0120] The bit error rate (BER) is a key indicator for evaluating the communication performance of the system, representing the ratio of the number of incorrect symbols to the total number of symbols during transmission, and representing the transmission quality of communication data. BER can be expressed as:

[0121]

[0122] The simulation result of the theoretical curve of the bit error rate of the MSK integrated signal based on the OFDM-LFM signal is as Figure 11 shown. It can be seen from the bit error rate curve that the bit error rate of the integrated signal is low and it has good communication performance.

[0123] The above-described embodiments merely represent specific implementation manners of the present application. Although the description is relatively specific and detailed, it should not be construed as a limitation on the protection scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the technical solution of the present application, several variations and improvements can be made, and these all fall within the protection scope of the present application.

[0124] This Background of the Invention section is provided to generally present the context of the present invention. Work of the presently named inventors, to the extent it is described in this Background of the Invention section, and aspects of the work described that were not part of the prior art as of the time of filing this application, are neither expressly nor impliedly admitted to be prior art to the present invention.

Claims

1. A sonar detection and communication integrated system based on OFDM-LFM signal, characterized in that: include: A transmitting transducer array for transmitting an OFDM-LFM integrated signal; A receiving hydrophone array is used to receive target echo signals and communication signals; Electronic compartment, used for generating OFDM-LFM integrated signals and signal processing.

2. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 1, characterized in that: The electronics compartment contains processing circuitry that performs the following operations: a. In the OFDM multi-carrier communication system, the frequency domain is divided into multiple mutually orthogonal sub-channels, and the detection function and the communication function are assigned non-overlapping sub-carrier sets; b. Use OFDM interleaved subcarrier allocation to allocate subcarrier resources to detection and communication functions; c. Generate an OFDM-LFM integrated signal through joint transmit beamforming for communication data; d. Demodulate the received target echo signal and communication signal to realize the target detection function and obtain communication data.

3. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 2 is characterized in that: The transmitting transducer array adopts a 1x4 linear array, consisting of 4 array elements with a half-wavelength interval. It is fixed by a bracket and forms a whole with the electronic warehouse.

4. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 3 is characterized in that: The receiving hydrophone array adopts a 3x4 array, consisting of 12 array elements with a half-wavelength spacing. It is fixed by a bracket and forms a whole with the electronic warehouse.

5. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 2 is characterized in that: At the transmitting end, communication and detection resources and power are first allocated based on the channel prediction results to form a transmit signal matrix. The signal is then sent after inverse discrete Fourier transform, cyclic prefix insertion, digital-to-analog conversion, and transmitting transducer array.

6. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 5, characterized in that: After receiving the signal, the communication user demodulates the signal on the communication resource block to obtain the communication data.

7. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 6, characterized in that: After the transmitted signal is reflected by the target, the receiving end receives the echo signal and correlates the received signal on the detection resource block with the original transmitted signal to achieve the target detection function.

8. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 1 is characterized in that: A portion of resources is optimally allocated for communication in each frame of multiple consecutive OFDM symbols, and the detection function consists of the concatenation of the remaining resources, where the energy budget is optimized in a subcarrier manner to ensure the high peak sidelobe ratio of the detection ambiguity function.

9. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 4, characterized in that: The transmitting transducer array and the receiving hydrophone array share a bracket.

10. The sonar detection and communication integrated system based on OFDM-LFM signal according to claim 2, characterized in that: The pulse repetition period in detection is represented by the duration of an OFDM signal, and multiple consecutive OFDM symbols are combined to extend the coherent processing interval.

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