Waveform space-time optimization method of low-interception multiple-input-multiple-output radar communication integrated system

Abstract

The invention provides a waveform space-time optimization method of a low-interception multiple-input-multiple-output radar communication integrated system, and relates to the technical field of radar communication. Firstly, a space-time joint optimization model is constructed by taking an actual transmitting beam pattern approaching an expected beam pattern as a target and considering a constant modulus constraint, a communication direction power constraint and an interference direction orthogonal constraint; and solving the space-time joint optimization model to obtain a transmitted waveform matrix. Through a phase encoding method, communication information is modulated in a transmitted waveform matrix, and a communication user receives a communication signal. According to the invention, while the radar detection performance is ensured, the concealment and the anti-interference capability of communication are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of radar communication, and more specifically relates to a waveform space-time optimization method for a low-interception multiple-input multiple-output radar communication integrated system. Background Technology

[0002] With the increasing imbalance between spectrum resource supply and demand and the continuous growth in demand for multifunctional electronic devices, the Integrated Sensing and Communications (ISAC) system, which combines radar detection and wireless communication functions, has become a research focus in the interdisciplinary field of communication and radar due to its core advantage of achieving dual-function integration based on a single hardware platform. Through the synergistic optimization of waveform design and signal processing technologies, this system can achieve efficient and reliable wireless data transmission while ensuring core radar detection performance (such as target detection accuracy and anti-interference capability), effectively overcoming the performance bottlenecks of traditional single-function systems. Traditional technical solutions have limitations in terms of communication rate improvement, anti-interference capability enhancement, and waveform orthogonality. The integrated sensing and communications system, through spatial-temporal joint coding, beamforming, and other technologies, can meet the dual needs of radar and communication in complex electromagnetic environments, improving the system's spectrum efficiency and stealth.

[0003] Multiple-Input Multiple-Output (MIMO) methods originated in the field of wireless communication and have since been widely applied to radar system design. MIMO radars utilize multiple transmit and receive antennas to independently transmit orthogonal waveforms, acquiring spatial diversity and waveform diversity gains, significantly improving system performance. Based on differences in antenna array layout, MIMO radars are mainly divided into two categories: co-located and distributed. Co-located MIMO radars have smaller antenna element spacing, offering significant advantages in beamforming accuracy, spatial resolution optimization, and coherent signal processing. Distributed MIMO radars, on the other hand, acquire richer spatial diversity information through wide-area deployment of antenna elements, effectively enhancing target detection probability and parameter estimation accuracy.

[0004] Compared to traditional phased array radars, multiple-input multiple-output (MIMO) radars offer significant advantages in terms of low probability of intercept, clutter suppression, and target tracking stability. The core challenge in waveform design lies in achieving flexible beamforming and anti-jamming capabilities while maintaining waveform orthogonality, providing a crucial technological foundation for integrated sensing and communication systems.

[0005] In existing waveform design methods for low-interception multiple-input multiple-output (MIMO) radar-communication integrated systems, the main approach is information embedding based on waveform parameter modulation. This method embeds communication data into the radar detection signal by modulating key parameters such as the amplitude, frequency, or phase of the MIMO radar's transmitted beam. Amplitude modulation maps communication bits to a beam weight vector, controlling the amplitude fluctuations of the radar beam sidelobes to transmit data. The receiver needs to demodulate the signal at a specific spatial angle. However, this method suffers from low communication rates, susceptibility to amplitude error interference, and high complexity in sidelobe level control, limiting its application in high-speed communication scenarios. Frequency modulation embeds information by switching carrier frequencies or changing the modulation slope. While maintaining radar detection performance, it has high hardware requirements and carries the risk of interception, necessitating time-varying rules to enhance security. Phase modulation maps communication bits to the phase parameters of the MIMO radar sub-pulses, transmitting data through phase changes in the transmitted signal. The receiver extracts phase features to demodulate the information. This method, with its constant envelope characteristic, ensures both the operational efficiency and detection performance stability of the radar transmitter, while avoiding the sidelobe level rise and system calibration difficulties caused by amplitude modulation. Furthermore, its transmission method, which conceals information within complex phase changes, offers stronger anti-interception capabilities compared to frequency modulation methods. However, due to the limited identifiability of signal characteristics, this method still carries the risk of being intercepted and deciphered by the enemy.

[0006] In summary, the existing waveform design methods for multi-input multi-output radar-communication integrated systems are insufficient in terms of low intercept performance, making it difficult for these systems to cope with complex electromagnetic environments and restricting their application in covert communication scenarios. Summary of the Invention

[0007] To address the shortcomings of current integrated multiple-input multiple-output (MIMO) radar-communication systems in terms of low intercept performance, this invention proposes a waveform space-time optimization method for integrated multiple-input multiple-output radar-communication systems with low intercept, which improves the stealth and anti-interference capabilities of communication while ensuring radar detection performance.

[0008] To achieve the above-mentioned technical effects, the technical solution of the present invention is as follows: This invention provides a waveform space-time optimization method for a low-interception multi-input multi-output (MIMO) radar-communication integrated system. The MIMO radar-communication integrated system includes: an integrated MIMO radar-communication platform, a detection target, a communication user, and active jamming. The integrated MIMO radar-communication platform is equipped with M antenna elements. The integrated waveform signal emitted by the M antenna elements propagates in space and is reflected back upon encountering the detection target. Simultaneously, the M antenna elements modulate the data information to be transmitted onto the communication user. The communication user receives and demodulates the data to obtain it. This method prevents the interception of communication information by one or more active jamming devices. The waveform space-time optimization method of the system includes the following steps: S1: With the goal of approximating the desired beam pattern to the actual transmitted beam pattern, a space-time joint optimization model is constructed, taking into account constant mode constraints, power constraints in the communication direction, and orthogonality constraints in the interference direction. S2: Solve the space-time joint optimization model to obtain the transmission waveform matrix; S3: The communication information is modulated into the transmitted waveform matrix using a phase coding method, and the communication user receives the communication signal.

[0009] Furthermore, in the integrated multi-input multi-output radar communication system, the integrated multi-input multi-output radar communication platform generates low intercept adaptation parameters, including: the information symbols to be transmitted. Signal code length N The number of constellation points L, and the interference suppression signal with orthogonal information symbols. v and the information symbol to be inserted ; Using QPSK modulation of the information symbols to be transmitted The corresponding information symbol to be inserted is obtained, and the expression is:

[0010] In the formula, This represents the QPSK communication symbol carried in the nth time unit.

[0011] Furthermore, the constant modulus constraint is used to maximize the transmission efficiency of the multi-input multi-output radar-communication integrated platform, and its expression is:

[0012] In the formula, Represents the selection matrix. Represents the transmitted waveform vector. This represents the total length of the transmitted waveform vector; The communication direction power constraint is used to maintain a constant transmitted signal power in the communication user direction, and its expression is:

[0013] In the formula, This represents the desired power value in the communication direction. Indicates the direction of the communication user. Represents the space-time coupling matrix in the communication direction; The interference direction orthogonality constraint is used to ensure that the transmitted signal approximates a reference signal orthogonal to the information symbol to be inserted in the direction of active interference. The expression is:

[0014] In the formula, The steering matrix indicating the direction of interference. A reference signal that is orthogonal to the communication information; The expression for the space-time joint optimization model is:

[0015] In the formula, This represents the total number of spatial angle sampling points. This represents the weight of the k-th angle point. Indicates the first k One spatial angle sampling point, Indicates the guide vector. Indicates the signal code length. This represents the k-th spatial angle sampling point.

[0016] Further, the specific operation of step S3 is as follows: using the ADMM algorithm, introducing the auxiliary variable t, optimizing the space-time joint optimization model, and performing iterative solution to obtain the transmission waveform matrix; The expression for the optimized space-time joint optimization model is as follows:

[0017] In the formula, t represents an auxiliary variable.

[0018] Furthermore, the expression for the transmitted waveform matrix is:

[0019] In the formula, S represents the transmitted waveform matrix, and M represents the number of transmitting antennas. Indicates the signal code length. The column vector represents the transmitted waveform matrix.

[0020] Furthermore, it also includes: based on the transmitted waveform matrix, the expression for calculating the transmitted beam pattern is:

[0021] In the formula, This indicates the transmitted beam pattern. Indicates the signal code length. Represents the transmitted waveform matrix. Indicates the transmitting antenna array in θ The directional guide vector.

[0022] Furthermore, the phase encoding method includes: direct phase mapping or phase rotation mapping.

[0023] Furthermore, the direct phase mapping method directly appends the phase of the information symbol to be inserted to the transmitted signal of the corresponding column of the transmitted waveform matrix S to obtain the received signal of the communication receiver. The phase rotation mapping method accumulates the phase of the information symbol to be inserted to obtain an accumulated phase vector, and then appends the accumulated phase vector to the transmitted signal of the corresponding column of the transmitted waveform matrix S to obtain the received signal of the communication receiver.

[0024] Furthermore, it also includes: S4: Communication user, which processes the received signal to obtain communication data of the multi-input multi-output radar communication integrated system.

[0025] Further, the operation steps of step S4 are as follows: when the received signal of the communication receiver is obtained by direct phase mapping, the received signal is phase compensated using the initial phase prior information, and the maximum likelihood criterion is used to make a decision on the phase compensated signal to obtain the communication data of the multi-input multi-output radar communication integrated system. When phase rotation mapping is used to obtain the received signal at the communication receiver, the accumulated phase of the information symbol is extracted by calculating the phase difference between adjacent pulse received signals. The maximum likelihood criterion is used to make a decision on the extracted phase, and the communication data of the multi-input multi-output radar communication integrated system is obtained.

[0026] Compared with existing technologies, the beneficial effects of this method are: This invention provides a waveform space-time optimization method for a low-interception multi-input multi-output (MIMO) radar-communication integrated system. First, aiming to approximate the desired beam pattern from the actual transmitted beam pattern, a space-time joint optimization model is constructed, considering constant mode constraints, communication direction power constraints, and interference direction orthogonality constraints. This model jointly optimizes waveform design, beamforming, and information encoding. Solving the space-time joint optimization model yields the transmitted waveform matrix and the transmitted beam pattern. Using phase encoding, communication information is modulated into the transmitted waveform matrix to obtain the received signal at the communication receiver. Finally, at the communication receiver, the received signal is processed to obtain the communication data of the MIMO radar-communication integrated system. This invention improves the stealth and anti-jamming capabilities of communication while maintaining radar detection performance. Attached Figure Description

[0027] Figure 1 A flowchart illustrating the waveform space-time optimization method for the low-interception multi-input multi-output radar-communication integrated system proposed in this embodiment of the invention; Figure 2 This is a model diagram of the multi-input multi-output radar-communication integrated system proposed in the embodiments of the present invention; Figure 3 The transmit beam pattern represents the waveform space-time optimization method for the low-interception multi-input multi-output radar-communication integrated system proposed in this embodiment of the invention. Figure 4 This diagram shows a comparison of the signal magnitudes of the communication direction signal and the interference direction signal proposed in this embodiment of the invention. Figure 5 A comparison diagram showing the cross-correlation values ​​of the communication direction signal and the interference direction signal proposed in the embodiments of the present invention; Figure 6 This represents the angle bit error rate analysis diagram proposed in the embodiments of the present invention. Detailed Implementation

[0028] The accompanying drawings are for illustrative purposes only and should not be construed as limiting the scope of this patent. To better illustrate this embodiment, some parts of the accompanying drawings may be omitted, enlarged, or reduced, and do not represent the actual dimensions; It is understandable to those skilled in the art that some well-known details may be omitted from the accompanying drawings.

[0029] The technical solution of the present invention will be further described below with reference to the accompanying drawings and embodiments.

[0030] The positional relationships depicted in the accompanying drawings are for illustrative purposes only and should not be construed as limiting this patent. Example 1 This invention provides a waveform space-time optimization method for a low-interception multi-input multi-output (MIMO) radar-communication integrated system. The MIMO radar-communication integrated system includes: an integrated MIMO radar-communication platform, a detection target, a communication user, and active jamming. The integrated MIMO radar-communication platform is equipped with a uniform linear array containing M antenna elements, where the transmission spacing d between the M antenna elements is half a wavelength, and the transmission angle of the M antenna elements is... The integrated waveform signal emitted by M antenna elements propagates in space, reflects back upon encountering the target, and simultaneously modulates the data information to be transmitted onto the communication user. The user receives and demodulates the data, thus preventing interception of communication information by one or more active interference sources. Figure 1The flowchart shown illustrates the method, and the system's waveform space-time optimization method includes the following steps: S1: With the goal of approximating the desired beam pattern to the actual transmitted beam pattern, a space-time joint optimization model is constructed, taking into account constant mode constraints, power constraints in the communication direction, and orthogonality constraints in the interference direction. S2: Solve the space-time joint optimization model to obtain the transmission waveform matrix; S3: The communication information is modulated into the transmitted waveform matrix using a phase coding method, and the communication user receives the communication signal.

[0031] In this embodiment, as Figure 2 The system model diagram shown illustrates a multi-input multi-output (MIMO) radar-communication integrated system, which includes: an integrated MIMO radar-communication platform, a target, a user, and active interference. The integrated MIMO radar-communication platform contains a base station, which comprises a uniform linear array (ULA) of M antenna elements with a transmission spacing of... d Half wavelength, emission angle is .

[0032] The integrated main lobe of the multi-input multi-output radar-communication system is used to transmit waveform signals that propagate through space and reflect back upon encountering a target. By processing the received echo signals, the system can extract the target's range, velocity (Doppler), and azimuth information. While transmitting detection signals into space, the radar also modulates the data information to be transmitted onto these radar waveforms and sends it to the communication user. The user can then receive and demodulate the data. When facing one or more active jamming devices, it is necessary to prevent their interception of communication information.

[0033] The integrated multi-input multi-output radar communication system generates low intercept adaptation parameters, including: the information symbols to be transmitted. The signal code length N, the number of constellation points L, the interference suppression signal v that is orthogonal to the information symbols, and the information symbol to be inserted. .in, The elements are 0 or 1. The length is The interference suppression signal v, which is orthogonal to the information symbols, is generated based on the number of active interferences, including one or more. It is vector The expression for the symbol of the m-th constellation point is:

[0034] In the formula, The complex symbol represents the m-th constellation point, and M represents the total number of constellation points; Using QPSK modulation of the information symbols to be transmitted The corresponding information symbol to be inserted is obtained, and the expression is:

[0035] In the formula, This represents the QPSK communication symbol carried in the nth time unit.

[0036] The constant modulus constraint is used to maximize the transmission efficiency of the multi-input multi-output radar-communication integrated platform, and its expression is:

[0037] In the formula, Represents the selection matrix. Represents the transmitted waveform vector. This represents the total length of the transmitted waveform vector.

[0038] In a multi-input multi-output (MIMO) radar-communication integrated system, the MIMO radar-communication integrated platform generates low intercept adaptation parameters, which are used as known quantities to input the space-time joint optimization model, serving as known quantities for constructing constraints and objective functions. The information symbol to be inserted is the direct object of phase coding (DCM / PRCM). The phase of the information symbol to be inserted is extracted to obtain the received signal at the communication receiver.

[0039] The communication direction power constraint is used to maintain a constant transmitted signal power in the communication user direction, and its expression is:

[0040] In the formula, This represents the desired power value in the communication direction. Indicates the direction of the communication user. Represents the space-time coupling matrix in the communication direction; The interference direction orthogonality constraint is used to ensure that the transmitted signal approximates a reference signal orthogonal to the information symbol to be inserted in the direction of active interference. The expression is:

[0041] In the formula, The steering matrix indicating the direction of interference. A reference signal that is orthogonal to the communication information; Based on low intercept adaptation parameters, and with the goal of approximating the desired beam pattern to the actual transmit beam pattern, considering constant mode constraints, communication direction power constraints, and interference direction orthogonality constraints, the expression of the space-time joint optimization model is as follows:

[0042] In the formula, This represents the total number of spatial angle sampling points. This represents the weight of the k-th angle point. Represents the transmitted waveform vector. This represents the k-th spatial angle sampling point. Indicates the guide vector. Represents the selection matrix. This represents the total length of the transmitted waveform vector. Indicates the signal code length. This represents the space-time coupling matrix in the communication direction. Indicates the direction of the communication user. This represents the desired power value in the communication direction. The steering matrix indicating the direction of interference. A reference signal that is orthogonal to the communication information. The game is played against a square matrix of size (MN+1), where all elements are 0 except for the (i,i)th element which is equal to 1. The expression for the transmitted waveform vector is:

[0043] In the formula, Represents the transmitted waveform matrix. Vectorization refers to the process of stacking a matrix column by column and converting it into a longer column vector.

[0044] The expression for the space-time coupling matrix in the communication direction is:

[0045] In the formula, This represents the space-time coupling matrix in the communication direction. This represents the selection matrix, used in long vectors. r Select the signals from all M antennas corresponding to the nth time chip; Represents the spatial correlation matrix.

[0046] The expression for the spatial correlation matrix is:

[0047] In the formula, This represents the guide vector.

[0048] The expression for the receiving guide vector is:

[0049] In the formula, This indicates the receiving guide vector.

[0050] The expression for the beam pattern approximation of the target matrix is:

[0051] In the formula, Indicates the desired beam pattern. This represents the matrix used to calculate the desired beam pattern.

[0052] The expression for the desired beam pattern calculation matrix is:

[0053] In the formula, Represents the identity matrix. Indicates the Kronecker product. Indicates the launch steering vector; The expression for the steering matrix in the direction of interference is:

[0054] In the formula, The steering matrix, which represents the direction of interference, is a The matrix.

[0055] Using the ADMM algorithm, an auxiliary variable t is introduced to optimize the space-time joint optimization model, and the transmission waveform matrix is ​​obtained by iterative solution. The expression for the optimized space-time joint optimization model is as follows:

[0056] In the formula, t represents an auxiliary variable; The expression for the transmitted waveform matrix is:

[0057] In the formula, S represents the transmitted waveform matrix, and M represents the number of transmitting antennas. Indicates the signal code length. The column vector represents the transmitted waveform matrix.

[0058] Based on the transmitted waveform matrix, the transmitted beam pattern of the integrated multi-input multi-output radar and communication system is calculated, and the expression is:

[0059] In the formula, This indicates the transmitted beam pattern. Indicates the signal code length. Represents the transmitted waveform matrix. Indicates the transmitting antenna array in θ The directional guide vector.

[0060] The transmit beam pattern transforms the optimized waveform matrix into a visible spatial energy distribution map, ultimately verifying and evaluating whether the system has achieved its design goals in radar detection, reliable communication, and low-interception (LIO) anti-jamming capabilities. Observing the main lobe of the beam pattern allows us to determine the radar's detection range, angular resolution, and detection distance. Observing the beam gain in the communication direction confirms whether the system outputs a sufficiently stable and powerful signal in that direction. Observing the gain levels in the sidelobes and interference directions assesses the system's stealth and anti-jamming capabilities.

[0061] In this embodiment, the constant modulus constraint introduced in the space-time joint optimization model ensures that the power amplifier always operates near the saturation region, thereby maximizing the amplifier's efficiency. To avoid the loss of information symbols during communication transmission, a constant power constraint in the communication direction is introduced to maintain a constant radiated power in the communication direction. For single or multiple active interferences in different directions, single or multiple signals orthogonal to the communication direction signal are generated. An approximation constraint between the interference direction signal and the orthogonal signal is introduced to minimize the impact of active interference on the communication direction.

[0062] S3: The communication information is modulated into the transmitted waveform matrix using a phase coding method, and the communication user receives the communication signal.

[0063] In the communication direction, the direct phase mapping method is used to extract the phase of the information symbol to be inserted. This signal is then directly appended to the corresponding column of the transmitted waveform matrix S to obtain the received signal at the communication receiver, expressed as:

[0064] In the formula, Represents the channel coefficient. A pulse transmission signal representing a specific moment in time; This indicates channel noise.

[0065] The phase rotation mapping method is used to accumulate the phase of the information symbol to be inserted to obtain the accumulated phase vector. The accumulated phase vector is then appended to the transmitted signal of the corresponding column of the transmitted waveform matrix S to obtain the received signal of the communication receiver.

[0066] The expression for the accumulated phase vector is: , In the formula, This represents the accumulated phase vector. .

[0067] The expression for the received signal at the communication receiver is: .

[0068] In the communication direction, to minimize the impact of communication symbols on the radar waveform, two phase encoding methods, Direct Phase Mapping (DCM) and Phase Rotation Mapping (PRCM), are used to attach communication information to the phase of the transmitted waveform. Due to the a priori nature of these two methods, decoding can only be performed in the communication direction, resulting in low interception characteristics in the space domain and enhancing system stealth.

[0069] Example 2 This embodiment, based on the waveform space-time optimization method for a low-interception multi-input multi-output radar communication integrated system proposed in Embodiment 1, further includes: S4: The communication user processes the received signal to obtain the communication data of the multi-input multi-output radar communication integrated system.

[0070] S4: The communication user processes the received signals to obtain the communication data of the integrated multi-input multi-output radar communication system.

[0071] Step S4 includes modulating the communication information onto the phase of the transmitted signal using a direct phase mapping encoding method or a phase rotation mapping encoding method.

[0072] To extract the embedded information symbols, the direct phase mapping method should first compensate for the initial phase. Because the communication stations are cooperative, the prior information about the initial phase can be accurately known at the communication receiver.

[0073] When using direct phase mapping to obtain the received signal at the communication receiver, firstly, phase compensation is performed on the received signal using known prior information about the initial phase. Then, the maximum likelihood criterion is applied to the phase-compensated signal to determine the final information symbol vector. This means obtaining the communication data of the multi-input multi-output radar communication integrated system.

[0074] The expression for the compensated received signal is:

[0075] In the formula, This indicates the received signal after compensation.

[0076] When phase rotation mapping is used to obtain the received signal at the communication receiver, the accumulated phase of the information symbol is extracted by calculating the phase difference between adjacent pulse received signals. The extracted phase is then evaluated using the maximum likelihood criterion to obtain the final information symbol vector. This refers to the communication data transmitted by the integrated radar and communication system.

[0077] The expression for the nth sub-pulse obtained by the communication receiver is:

[0078] In the formula, This represents the phase of the nth sub-pulse, where n = 1, 2, ..., N. Indicates channel gain. Indicates signal power. Indicates the initial phase of the communication signal. The accumulated phase of the information symbol minus the current initial phase effectively cancels out the initial phase of the communication signal, leaving only the accumulated phase of the information symbol. After obtaining the phase of the information symbol, the phase of the constellation points is determined using the maximum likelihood criterion to obtain the final information symbol, thus obtaining the communication data of the multi-input multi-output radar-communication integrated system.

[0079] Example 3 In this embodiment, a simulation experiment is conducted on the waveform space-time optimization method of a low-interception multiple-input multiple-output radar-communication integrated system proposed in Embodiments 1 and 2 to demonstrate the effectiveness of the proposed waveform design method.

[0080] In this embodiment, the wavelength of the multi-input multi-output radar-communication integrated system is set to 3 cm, and the element spacing is half a wavelength. The system employs a uniform linear array containing 10 elements (M = 10); the transmitted signal code length is 32 (N = 32); the communication direction is set to -20°. The interference direction is 60°. The radar main lobe width is 20°, and the center is located at 10°. like Figure 3 The transmitted beam pattern shown illustrates the waveform space-time optimization method for a low-intercept multiple-input multiple-output radar-communication integrated system. This method effectively approximates the desired beam pattern through shape approximation, resulting in a transmitted beam pattern with concentrated main lobe energy and good matching with the ideal beam pattern. It maintains approximately -6dB of gain in the communication direction, ensuring that the radiated power in that direction remains essentially unchanged. Simultaneously, the beam sidelobes are low with minimal energy distribution, effectively avoiding interference with the main lobe performance.

[0081] like Figure 4 The diagram shows a comparison of the signal magnitudes of the communication direction signal and the jamming direction signal. The waveform space-time optimization method for the low-interception multi-input multi-output radar-communication integrated system proposed in this application designs a communication direction signal with constant-modulus constraint characteristics. Compared to the jamming direction signal, this constraint effectively prevents nonlinear distortion of the power amplifier, thereby maximizing transmitter efficiency, and facilitating the embedding of information symbols through phase coding to support communication functions. Figure 5The diagram showing the cross-correlation values ​​of the communication direction signal and the interference direction signal illustrates the simulation results of their correlation. Compared to the cross-correlation value between the communication direction signal and its orthogonal signal, the cross-correlation value between the communication direction signal and the interference direction signal, while slightly increased, remains consistently below -10 dB. This result demonstrates that the method proposed in this application can effectively suppress the influence of the interference direction signal on the communication direction signal, exhibiting excellent interference isolation performance.

[0082] like Figure 6 As shown in the angle bit error rate analysis diagram, the bit error rate characteristics in the spatial domain are simulated using the present invention. The two coding schemes of the multi-input multi-output radar communication integrated system involved in the present invention, namely direct phase mapping (DCM) and phase rotation mapping (PRCM), have low bit error rates only in the communication direction and high bit error rates in other directions, thus having inherent anti-interception security in the entire spatial domain.

[0083] In the integrated radar-communication scenario, a space-time joint optimization model is used to jointly optimize waveform design, beamforming (spatial domain), and information encoding (temporal domain) as a whole. Orthogonal constraints are applied to the communication direction signal and the active interference direction signal to reduce their cross-correlation and minimize the impact of active interference on the communication direction signal. Two phase encoding methods, Direct Phase Mapping (DCM) and Phase Rotation Mapping (PRCM), are used to directly modulate the communication information onto the radar signal phase, ensuring that the communication information is correctly demodulated only in the communication direction and exhibiting a high bit error rate in the interference direction, thereby achieving inherent anti-interception security in the spatial domain.

[0084] The embodiments described are merely examples to clearly illustrate the present invention and are not intended to limit the implementation of the invention. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively describe all possible implementations. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A waveform space-time optimization method for a low-interception multiple-input multiple-output (MIMO) radar-communication integrated system, wherein the MIMO radar-communication integrated system comprises: The system comprises a multi-input multi-output (MIMO) radar-communication integrated platform, a detection target, a communication user, and active jamming. The MIMO radar-communication integrated platform is equipped with M antenna elements. The integrated waveform signal emitted by the M antenna elements propagates in space, is reflected back upon encountering the detection target, and simultaneously modulates the data information to be transmitted onto the communication user. The communication user receives and demodulates the data. The system prevents the interception of communication information by one or more active jamming devices. The system's waveform space-time optimization method includes the following steps: S1: With the goal of approximating the desired beam pattern to the actual transmitted beam pattern, a space-time joint optimization model is constructed, taking into account constant mode constraints, power constraints in the communication direction, and orthogonality constraints in the interference direction. S2: Solve the space-time joint optimization model to obtain the transmission waveform matrix; S3: The communication information is modulated into the transmitted waveform matrix using a phase coding method, and the communication user receives the communication signal.

2. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 1, characterized in that, The integrated multi-input multi-output radar communication system generates low intercept adaptation parameters, including: the information symbols to be transmitted. Signal code length N The number of constellation points L, and the interference suppression signal with orthogonal information symbols. v and the information symbol to be inserted ; Using QPSK modulation of the information symbols to be transmitted The corresponding information symbol to be inserted is obtained, and the expression is: In the formula, This represents the QPSK communication symbol carried in the nth time unit.

3. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 1, characterized in that, The constant modulus constraint is used to maximize the transmission efficiency of the multi-input multi-output radar-communication integrated platform, and its expression is: In the formula, Represents the selection matrix. Represents the transmitted waveform vector. This represents the total length of the transmitted waveform vector; The communication direction power constraint is used to maintain a constant transmitted signal power in the communication user direction, and its expression is: In the formula, This represents the desired power value in the communication direction. Indicates the direction of the communication user. Represents the space-time coupling matrix in the communication direction; The interference direction orthogonality constraint is used to ensure that the transmitted signal approximates a reference signal orthogonal to the information symbol to be inserted in the direction of active interference. The expression is: In the formula, The steering matrix indicating the direction of interference. A reference signal that is orthogonal to the communication information; The expression for the space-time joint optimization model is: In the formula, This represents the total number of spatial angle sampling points. This represents the weight of the k-th angle point. Indicates the first k One spatial angle sampling point, Indicates the guide vector. Indicates the signal code length. This represents the k-th spatial angle sampling point.

4. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 3, characterized in that, The specific operation of step S3 is as follows: using the ADMM algorithm, introducing the auxiliary variable t, optimizing the space-time joint optimization model, and performing iterative solution to obtain the transmission waveform matrix; The expression for the optimized space-time joint optimization model is as follows: In the formula, t represents an auxiliary variable.

5. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 4, characterized in that, The expression for the transmitted waveform matrix is: In the formula, S represents the transmitted waveform matrix, and M represents the number of transmitting antennas. Indicates the signal code length. The column vector represents the transmitted waveform matrix.

6. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 5, characterized in that, Also includes: Based on the transmitted waveform matrix, the expression for calculating the transmitted beam pattern is: In the formula, This indicates the transmitted beam pattern. Indicates the signal code length. Represents the transmitted waveform matrix. Indicates the transmitting antenna array in θ The directional guide vector.

7. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 1, characterized in that, The phase encoding method includes: direct phase mapping or phase rotation mapping.

8. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 7, characterized in that, The direct phase mapping method involves directly attaching the phase of the information symbol to be inserted to the transmitted signal in the corresponding column of the transmitted waveform matrix S to obtain the received signal at the communication receiver. The phase rotation mapping method accumulates the phase of the information symbol to be inserted to obtain an accumulated phase vector, and then appends the accumulated phase vector to the transmitted signal of the corresponding column of the transmitted waveform matrix S to obtain the received signal of the communication receiver.

9. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 8, characterized in that, Also includes: S4: The communication user processes the received signals to obtain the communication data of the integrated multi-input multi-output radar communication system.

10. The waveform space-time optimization method for a low-interception multiple-input multiple-output radar-communication integrated system according to claim 9, characterized in that, The operation steps of step S4 are as follows: when the received signal of the communication receiver is obtained by direct phase mapping, the phase compensation of the received signal is performed using the initial phase prior information, and the maximum likelihood criterion is used to make a decision on the phase-compensated signal to obtain the communication data of the multi-input multi-output radar communication integrated system. When phase rotation mapping is used to obtain the received signal at the communication receiver, the accumulated phase of the information symbol is extracted by calculating the phase difference between adjacent pulse received signals. The maximum likelihood criterion is used to make a decision on the extracted phase, and the communication data of the multi-input multi-output radar communication integrated system is obtained.

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