Pseudo-random time modulation four-dimensional antenna array multi-target secure communication method and system

Abstract

The present invention discloses a multi-target secure communication system based on a pseudo-random time-modulated four-dimensional antenna array, which includes a four-dimensional wave control module, a modulation timing generator, a baseband modulation module, a mixer, a power divider, a radio frequency modulation switch, a filter, a power amplifier, an antenna element, and optical fibers and cables connecting various parts; since operations such as time modulation and filtering are performed before the power amplifier amplifies, the power loss caused by either time modulation or filtering is small and can be approximately ignored. The present invention also discloses a multi-target secure communication method based on a pseudo-random time-modulated four-dimensional antenna array. This method can perform digital-analog hybrid pseudo-random modulation on the original signal by jointly utilizing the digital baseband and analog time modulation degrees of freedom, so as to transmit different original undistorted signals in multiple desired directions, while the signals in non-desired directions are pseudo-randomly disturbed and distorted, thereby realizing secure communication transmission for multiple targets simultaneously.

Description

Technical Field

[0001] The present invention belongs to the technical field of antenna engineering, relates to the field of wireless communication, and specifically designs a physical layer secure communication system and method for multi-target users based on four-dimensional antenna array technology, which can be used in secure communication systems requiring high security performance and simultaneous multi-target transmission. Background Art

[0002] In 1963, American scholars Kummer et al. proposed the concept of time-modulated antenna array: by continuously changing the antenna state over time, the radiation aperture size of the antenna can be controlled in the "time" dimension. The time-modulated antenna array belongs to a type of four-dimensional antenna array. The four-dimensional antenna array uses high-speed RF switches, high-speed amplitude-phase modulators, mixers, etc. to control the working state of each unit according to a predetermined working timing, so that the radiation state of the antenna array changes over time, that is, it has time modulation characteristics, thus greatly increasing the design freedom of the antenna array. The four-dimensional antenna array has great advantages in direction modulation and shaped beam, and many achievements have been made. In recent years, the engineering application research of four-dimensional antenna arrays has been increasingly valued. There are currently literature reports on the applications of four-dimensional antenna arrays in simultaneous multi-beam scanning, secure communication, low probability of intercept radar, etc. As a new type of array antenna with strong design flexibility, four-dimensional antennas have very large application space and potential advantages in the fields of RF stealth radar and communication.

[0003] Different from the transmission confidentiality of wired communication, in traditional wireless communication systems, the antenna radiates signals in free space, and most of the signal characteristics of the radiated signals in different directions are the same, resulting in the signals being extremely easy to be eavesdropped by illegal receivers. Therefore, to prevent eavesdropping, many scholars in related fields have proposed many methods to achieve secure communication.

[0004] In the patent with the publication number CN 105553641 A, a chaotic secure communication method and a secure communication system are proposed. This system uses chaotic masking technology and selects a high-power chaotic masking signal to mask the chaotic keying signal. However, this system needs to shake hands with the legitimate receiver before working to determine the working protocol, working mode, and the selection strategy of the working mode. If an illegal receiver steals the working protocol, mode, etc. of this system, the security system of this system will be greatly reduced. In addition, due to the need to radiate an additional high-power masking signal, the overall transmission efficiency of the system is not high.

[0005] In the patent with the publication number CN 109996231 A, a secure communication method in a multi-antenna system was proposed. This method combines spatial modulation technology and uses the antennas not selected in spatial modulation technology to transmit interference signals. The legitimate receiver knows the antenna serial numbers that transmit useful information, so it can normally recover and demodulate the signals. Since the illegal receiver does not know the serial numbers of the useful antennas in advance, it is difficult to separate the interference from the received signals, and thus it is difficult to recover the correct information. However, this method requires the legitimate receiver to receive information about the useful antenna sequence in advance. If the illegal receiver steals the information of the useful antenna sequence or guesses it through other algorithms, the security performance of this method will also drop sharply.

[0006] In the patent with the publication number CN 110890908 B, a secure communication system and method based on a pre-modulated four-dimensional antenna array were disclosed. By combining direction modulation technology and beamforming technology, while ensuring the performance of direction modulation, the average radiation power in the sidelobe range was effectively regulated, thereby reducing the probability of the radiation signal being intercepted by an illegal receiver. However, this method can only generate a single beam to serve a single desired communication target and is difficult to cope with the more common multi-target communication scenarios.

[0007] In the patent with the publication number CN 113114321 B, a space-time joint modulation secure communication system and method based on a four-dimensional antenna array were disclosed. By making full use of the space-time degrees of freedom of the antenna system, the modulation of the communication signal is divided into two parts. One part is baseband modulation, which is completed at the baseband digital end. The other part is antenna modulation, which has a direction-dependent characteristic and is achieved by modulating the antenna elements. In this way, an undistorted joint modulation signal can be transmitted in the desired direction, while a distorted joint modulation signal is transmitted in the non-desired direction. However, this method can also only generate a single beam to serve the target in a single desired direction and is difficult to be used in multi-target scenarios.

[0008] In the patent with the publication number CN 110493777 B, a multi-target secure communication system based on a four-dimensional antenna array was disclosed. By optimizing the control timing of the system antenna elements, the different harmonic direction patterns radiated by the antenna array point to different target users, thus realizing multi-target secure communication. However, the three-state time modulation switch used in this system has a relatively high complexity, its harmonic direction patterns are at different frequencies, and its beam control degrees of freedom are relatively low, making it difficult to cope with scenarios with a large number of targets.

[0009] Facing the above application requirements, the present invention discloses a multi-target secure communication method and system for a pseudo-random time modulation four-dimensional antenna array. By jointly leveraging the digital baseband and analog time modulation degrees of freedom, the original signal is subjected to digital-analog hybrid pseudo-random modulation, thereby transmitting different original undistorted signals in multiple desired directions, while the signals in non-desired directions are pseudo-randomly scrambled and distorted, thus achieving secure communication transmission for multiple targets simultaneously. This method fully exploits the digital baseband and analog time modulation degrees of freedom of the four-dimensional antenna array and realizes secure communication transmission for multiple targets simultaneously with relatively low hardware complexity. Summary of the Invention

[0010] The present invention is realized in view of the above background, overcomes the deficiencies of the prior art, and proposes a multi-target secure communication method and system for a pseudo-random time modulation four-dimensional antenna array, effectively improving the multi-target secure transmission ability of the physical layer secure communication system.

[0011] To achieve the above invention objectives, the present invention adopts the following technical solutions. Consider an N-element four-dimensional antenna array, whose time-domain radiation field can be expressed as

[0012]

[0013] where f0 is the carrier frequency, N represents the number of antenna elements, U k (t) represents the modulation function of the k-th element, β represents the wave number in free space (usually β = 2π / λ can be set, where λ represents the wavelength in free space), d represents the spacing between adjacent elements, θ represents the angular direction, t represents time, e represents the natural base, and j represents the imaginary unit.

[0014] When U k (t) is considered as a periodic function, the radiation field of the four-dimensional antenna array can be expanded in the frequency domain as:

[0015]

[0016] where,

[0017]

[0018] where a mk represents the equivalent complex excitation of the k-th element at the m-th sideband, including the amplitude term and the phase term, f s represents the modulation frequency of the timing signal, T s represents the modulation period of the timing signal, t k represents the starting time of conduction, τ k represents the conduction duration. In particular, when m = 0, a 0k = τ k , that is, equal to the duty cycle of this timing, and the center frequency radiation can be expressed as:

[0019]

[0020] It can be found from the above formula that the central frequency pattern is independent of the time modulation frequency / cycle and is mainly related to the duty cycle of the modulation timing. The duty cycle is also the equivalent weighting coefficient of the central frequency beam.

[0021] Assume that s(t) is the baseband modulation signal to be transmitted, and the radiation field of the four-dimensional antenna array carrying the baseband signal can be expressed by the formula

[0022]

[0023] Assume that s p (t) is the p-th original signal to be transmitted to the direction of θ p . The baseband pre-modulation signal of s p (t) is represented by h p (t). Then the total baseband modulation signal s(t) to be transmitted is formed by combining the signals of each path after pre-modulation, and it can be further expressed as:

[0024]

[0025] where Q represents the number of signal paths to be transmitted. To achieve multi-target secure communication transmission, here h p (t) can be expressed as:

[0026]

[0027] In this way, the radiation field of the four-dimensional antenna array with the baseband signal s(t) can be expressed as:

[0028]

[0029] Substituting Equation (1) into it, the above formula can be written as:

[0030]

[0031] Observing the above formula, it can be seen that in the direction of θ p , the numerator and denominator of the right half of the formula are the same and can be cancelled out, so that the influence of the baseband pre-modulation and time modulation on the signal s p in the direction of θ p (t) cancels each other out, and the signal s p (t) is transmitted to the direction of θ p without distortion. In this way, by designing the timing, the signals in the remaining non-expected directions except the expected direction can be modulated with the maximum randomness while maintaining a low sidelobe radiation, so as to achieve simultaneous multi-target secure communication transmission.

[0032] Assume that the desired targets are scattered throughout the entire airspace. If “1” represents that the modulation switch is turned on and “0” represents that the modulation switch is turned off, then the simultaneous multi-target secure transmission timing needs to be pseudo-randomly generated after satisfying the following constraints:

[0033]

[0034] The most significant feature of its timing is that only one unit is in the on-excitation state at any given time, which means that the radiation energy can be distributed throughout the entire airspace and cover all desired targets. At this time, the radiation field represented by Equation (9) can be written as:

[0035]

[0036] It can be found from the above equation that different signals s p (t) are respectively radiated by a beam pointing in the direction of θ p , and this beam is pseudo-randomly time-modulated by U k (t). Therefore, the p-th beam for transmitting s p (t) can be written separately as:

[0037]

[0038] At this time, in the desired direction θ p , Equation (12) can be further simplified as:

[0039]

[0040] It can be found that at this time the signal is not time-modulated and can be correctly demodulated. In the non-desired direction, the signal is pseudo-randomly time-modulated by U k (t), which disperses the energy pseudo-randomly over the spectrum. This makes it difficult for the signal in the non-desired direction to be eavesdropped by the eavesdropping machine, ensuring good secure transmission performance. On the other hand, although through pseudo-random modulation, the energy in the non-desired direction is dispersed over the spectrum, the radiation energy at its center frequency still carries a large amount of original information. Therefore, it is also necessary to specifically suppress the radiation at the center frequency.

[0041] Observing Equation (4), it can be found that regardless of how the modulation frequency changes, the equivalent amplitude weighting of the beam at the center frequency is always equal to its duty cycle. Therefore, by controlling the duty cycle, the sidelobe levels of multiple radiation beams located at the center frequency can be effectively suppressed simultaneously. At this time, the pseudo-random timing function can be split into multiple pulse translation timings. When generating this pseudo-random timing, in addition to satisfying the relationship shown in Equation (10), the following conditions also need to be satisfied:

[0042]

[0043] Where T w represents the w-th observation period split from the pseudo-random time sequence, and τ k,w represents the time-sequential conduction duty cycle of the k-th unit within the w-th observation period, which is also the equivalent weighting coefficient of the central frequency beam. In this way, by controlling the conditions for generating the pseudo-random time sequence, the radiation energy of the central frequency pattern in the non-expected direction can be effectively suppressed, and the aliasing interference is pseudo-randomly generated to effectively hide multiple true transmission messages, realizing simultaneous multi-target secure communication transmission.

[0044] Based on the above principle, the present invention discloses a pseudo-random time modulation four-dimensional antenna array multi-target secure communication system, which includes a four-dimensional wave control module, a modulation time sequence generator, a baseband modulation module, a mixer, a power divider, a radio frequency modulation switch, a filter, a power amplifier, antenna elements, and optical fibers and cables connecting various parts; the four-dimensional wave control module is connected to the modulation time sequence generator and the baseband modulation module, the baseband modulation module is connected to the mixer, the power divider is connected to each radio frequency modulation switch, each radio frequency switch is respectively connected to the filter, and then each filter is connected to the power amplifier, and the power amplifier is connected to each antenna element, and the final signal is radiated by each antenna element; among them, the four-dimensional wave control module is composed of a time sequence generation module and a pre-modulation signal generation module; the time sequence generation module is used to generate a corresponding pseudo-random time sequence according to the established beam requirements and output it to the modulation time sequence generator, and the modulation time sequence generator generates a pseudo-random modulation time sequence signal for controlling the radio frequency modulation switch and sends it to the radio frequency modulation switch, and the pre-modulation signal generation module is used to generate specified pre-modulation signal information according to the time sequence information and the expected target direction information and transmit it to the baseband modulation module; the baseband modulation module performs baseband modulation on the received pre-modulation signal information and the original signal information and then sends the signal to the mixer; the mixer is used to up-convert the baseband-modulated signal and transmit it to the power divider; the power divider is used to divide the input signal and send it to the radio frequency switches of each channel; the radio frequency switch is used to perform time modulation on the input radio frequency signal according to the received time sequence; the filter is used to filter out the out-of-band useless radiation signals and reduce the probability of signal eavesdropping; the power amplifier is used to amplify the filtered radio frequency signal and transmit it to the antenna element, and finally the signal is radiated by the antenna element.

[0045] Based on the above principle, the present invention also discloses a pseudo-random time modulation four-dimensional antenna array multi-target secure communication method, which includes the following steps:

[0046] (1) The four-dimensional wave control module generates modulation time sequence information and pre-modulation signal information according to the expected target direction and sends them into the modulation time sequence generator and the baseband modulation module respectively;

[0047] (2) The baseband modulation module performs baseband modulation according to the received pre-modulated signal information and the original signal information to be transmitted, and then sends the modulated signal to the mixer;

[0048] (3) The mixer up-converts the baseband modulated signal into a radio frequency signal and then sends it to the power splitter, which splits the radio frequency signal into each radio frequency modulation switch;

[0049] (4) The radio frequency modulation switch performs pseudo-random time modulation on the incoming radio frequency signal according to the pseudo-random timing control signal generated by the modulation timing generator;

[0050] (5) The signal after time modulation is successively filtered by a filter to remove out-of-band useless radiation, amplified by a power amplifier, and then radiated by each antenna element.

[0051] By combining the baseband modulation degree of freedom and the time modulation degree of freedom, multiple original information signals are pre-modulated by the baseband and time-modulated by the switch, and then mapped to different units for radiation according to the established transmission direction. Finally, different original information signals are transmitted in different desired directions, realizing simultaneous multi-target secure communication transmission. Since operations such as time modulation and filtering are performed before the power amplifier amplifies, the power loss caused by either time modulation or filtering is small and can be approximately ignored. On the other hand, because pseudo-random time modulation is adopted, the randomness of the timing is maximized, making it difficult for illegal receivers to demodulate the original signal information by deciphering the timing information. In addition, since the useful signals transmitted in different directions after baseband modulation and time modulation are all at the same center frequency, out-of-band useless signals can be filtered by a filter to further ensure the transmission security performance. Description of the Drawings

[0052] Figure 1 It is a schematic structural diagram of a multi-target secure communication system for a pseudo-random time modulation four-dimensional antenna array;

[0053] Figure 2 It is a multi-beam timing schematic diagram, where the white part indicates that the unit is turned on and the black indicates that it is turned off;

[0054] Figure 3 It is the comparison result of the original signal and the demodulated signal in the corresponding direction after the user receivers in different directions receive and demodulate the signals. It can be found that the original signals to be transmitted can be normally demodulated in each desired direction;

[0055] Figure 4 It is the bit error rate curve of the received demodulated signals in each direction for each original signal. It can be found that each original signal to be transmitted can only be correctly demodulated in its corresponding desired direction, and in non-desired directions, it is difficult to demodulate and identify the original signal information;

[0056] Figure 5 Figure for the angle-frequency dimensional radiation power of 5 beams generated by the four-dimensional antenna array using the conventional multi-harmonic beam generation method. It can be seen that the traditional multi-harmonic beams of the traditional four-dimensional antenna array are not only at different sideband frequencies, but also their spectral distributions are relatively regular and are easily eavesdropped by illegal receivers;

[0057] Figure 6 Figure for the angle-frequency dimensional radiation power of 5 beams radiated by the system proposed by the present invention. It is easy to find that the multi-beams emitted by the four-dimensional antenna array system proposed by the present invention are located at the same center frequency, and their spectral distributions at different angles are relatively random and are difficult to be eavesdropped by illegal receivers;

[0058] Figure 7 Figure for the angle-frequency dimensional radiation power when the system proposed by the present invention emits 5 different QPSK signals. It can be seen from the figure that the overall radiation power distribution of the system after loading the QPSK signal to be transmitted has strong randomness and can effectively resist the eavesdropping of illegal receivers in all directions; Specific implementation scheme

[0059] The embodiment consists of 16 uniformly arranged antenna elements, and the element spacing is half a wavelength. Figure 1The schematic diagram of the multi-target secure communication system for a pseudo-random time-modulated four-dimensional antenna array is given. The system includes a four-dimensional wave control module, a modulation timing generator, a baseband modulation module, a mixer, a power divider, a radio frequency (RF) modulation switch, a filter, a power amplifier, antenna elements, and optical fibers and cables connecting various parts. The four-dimensional wave control module is connected to the modulation timing generator and the baseband modulation module. The baseband modulation module is connected to the mixer. The power divider is connected to each RF modulation switch. Each RF switch is then connected to a filter respectively. Subsequently, each filter is connected to a power amplifier. The power amplifier is connected to each antenna element, and the final signal is radiated by each antenna element. Among them, the four-dimensional wave control module consists of a timing generation module and a pre-modulation signal generation module. The timing generation module is used to generate corresponding timing according to the established beam requirements and output it to the modulation timing generator. The modulation timing generator generates signals for controlling the RF modulation switch and sends them to the RF modulation switch. The pre-modulation signal generation module is used to generate specified pre-modulation signal information according to the timing information and the desired target direction information and transmit it to the baseband modulation module. The baseband modulation module performs baseband modulation on the received pre-modulation signal information and the original signal information and then sends the signal to the mixer. The mixer is used to up-convert the baseband-modulated signal and transmit it to the power divider. The power divider is used to divide the input signal and send it to the RF switches in each channel. The RF switch is used to perform time modulation on the input RF signal according to the received timing. The filter is used to filter out out-of-band useless radiation signals and reduce the probability of signal eavesdropping. The power amplifier is used to amplify the filtered RF signal and transmit it to the antenna element, and finally the signal is radiated by the antenna element.

[0060] Suppose there are 5 different original signals to be transmitted, which are Quadrature Phase Shift Keying (QPSK) signals with a baud rate of 10 Mbps and a carrier frequency f0 = 3 GHz. Among them, the 5 different signals are respectively transmitted to five different directions of (-30°, -20°, 0°, 20°, 40°).

[0061] First, the four-dimensional wave control module generates timing information and pre-modulation signal information according to the desired target direction and quantity, and transmits them to the modulation timing generator and the baseband modulation module respectively. The modulation timing generator generates corresponding modulation timing according to the received timing information to control each RF modulation switch for time modulation. The generated timing signal is as Figure 2As shown in the figure. The baseband modulation module pre-modulates the original information signal to be transmitted according to the received pre-modulation signal information and the signal information to be transmitted, and then transmits the modulated baseband signal to the mixer for up-conversion, and then sends the obtained radio frequency signal to the power divider for power division operation; after the power divider divides the signal, it is transmitted to the radio frequency modulation switch for time modulation; the radio frequency modulation switch transmits the time-modulated signal to the filter, and the filter filters out the invalid sideband signal and then transmits the signal to the power amplifier for amplification; the power amplifier amplifies the signal and transmits it to each antenna unit, and each antenna unit radiates it. The user receivers in different directions receive the signals and perform demodulation. The comparison result between the original signal and the demodulated signal in the corresponding direction is as follows Figure 3 As shown in the figure. It can be found from the figure that the original signals to be transmitted corresponding to each desired direction can be normally demodulated. Figure 4 The bit error rate curves of the received demodulated signals in each direction for each original signal are given. It can be seen from this that each original signal to be transmitted can only be correctly demodulated in its corresponding desired direction, while in the non-desired directions, it is difficult to demodulate and identify the original signal information.

[0062] In addition, Figure 5 The schematic diagram of the radiation power in the angle-frequency dimension of generating 5 beams by the four-dimensional antenna array using the conventional multi-harmonic beam generation method is drawn. Figure 6 The schematic diagram of the radiation power in the angle-frequency dimension of the 5 beams radiated by the system proposed in the present invention is given. Comparing the above two figures, it can be seen that the conventional multi-harmonic beams of the traditional four-dimensional antenna array are not only at different sideband frequencies, but also their spectral distributions are relatively regular and are easy to be eavesdropped by illegal receivers; on the contrary, the multi-beams emitted by the four-dimensional antenna array system proposed in the present invention are located at the same center frequency, and their spectral distributions at different angles are relatively random and are difficult to be eavesdropped by illegal receivers. Figure 7 The schematic diagram of the radiation power in the angle-frequency dimension when the system proposed in the present invention emits 5 different QPSK signals is shown. It can be seen from the figure that the overall radiation power distribution of the system after loading the QPSK signal to be transmitted has strong randomness and can effectively resist the eavesdropping of illegal receivers in all directions. It is worth mentioning that since the proposed system can cope with multiple target communication users, it has a wider application prospect in actual wireless communication applications.

[0063] A specific embodiment of the present invention has been described above. It should be understood that this is only presented in an exemplary form and is not restrictive. Therefore, various changes in form and details can be made without departing from the spirit and scope of the present invention, which is obvious to those skilled in the art and does not require creative labor. All of the above should be regarded as the scope involved in the present invention.

Claims

1. A method for multi-target secure communication of a pseudo-random time-modulated four-dimensional antenna array, characterized in that, It is realized by a multi-target secure communication system using a pseudo-random time modulation four-dimensional antenna array. The system includes a four-dimensional wave control module, a modulation timing generator, a baseband modulation module, a mixer, a power divider, a radio frequency modulation switch, a filter, a power amplifier, antenna elements, and optical fibers and cables connecting all parts. The four-dimensional wave control module is connected to the modulation timing generator and the baseband modulation module. The baseband modulation module is connected to the mixer. The power divider is connected to each radio frequency modulation switch. Each radio frequency switch is then respectively connected to a filter. Then each filter is connected to a power amplifier. The power amplifier is connected to each antenna element, and the final signal is radiated by each antenna element. Among them, the four-dimensional wave control module consists of a timing generation module and a pre-modulation signal generation module. The timing generation module is used to generate corresponding pseudo-random timing according to the established beam requirements and output it to the modulation timing generator. The modulation timing generator generates a pseudo-random modulation timing signal for controlling the radio frequency modulation switch and sends it to the radio frequency modulation switch. The pre-modulation signal generation module is used to generate specified pre-modulation signal information according to the timing information and the desired target direction information and transmit it to the baseband modulation module. The baseband modulation module performs baseband modulation on the received pre-modulation signal information and the original signal information and then sends the signal to the mixer. The mixer is used to up-convert the baseband modulated signal into a radio frequency signal and transmit it to the power divider. The power divider is used to divide the input signal and send it into the radio frequency switches of each channel. The radio frequency switch is used to perform pseudo-random time modulation on the input radio frequency signal according to the received timing. The filter is used to filter out out-of-band useless radiation signals and reduce the probability of the signal being eavesdropped. The power amplifier is used to amplify the filtered radio frequency signal and transmit it to the antenna element, and finally the signal is radiated by the antenna element. The method includes the following steps: S1. The four-dimensional wave control module generates modulation timing information and pre-modulation signal information according to the desired target direction and sends them into the modulation timing generator and the baseband modulation module respectively; S2. The baseband modulation module performs baseband modulation according to the received pre-modulation signal information and the original signal to be transmitted, and then sends the modulated signal into the mixer; S3. The mixer up-converts the baseband modulated signal into a radio frequency signal and sends it into the power divider. The power divider distributes the radio frequency signal to each radio frequency modulation switch; S4. The radio frequency modulation switch performs pseudo-random time modulation on the incoming radio frequency signal according to the pseudo-random timing control signal generated by the modulation timing generator; S5. The signal after time modulation passes through the filter to filter out out-of-band useless radiation and the power amplifier to amplify the signal in sequence, and then is radiated by each antenna element; The pseudo-random timing can be split into multiple pulse translation timings. By controlling the conditions for generating the pseudo-random timing, the radiation energy of the center frequency pattern in the non-expected direction can be effectively suppressed, and pseudo-random aliasing interference can be generated to effectively hide multiple real transmission information. When generating the pseudo-random timing, the following two conditions need to be met simultaneously: Condition 1: Condition 2: Among them, U k (t) represents the modulation function of the k-th unit, T w represents the w-th observation period split from the pseudo-random time series, τ k,w represents the time series conduction duty cycle of the k-th unit within the w-th observation period, which is also the equivalent weighting coefficient of the center frequency beam.

2. The method for multi-target secure communication of the pseudo-random time-modulated four-dimensional antenna array according to claim 1, further characterized in that Because pseudo-random time modulation is adopted, the randomness of the timing is maximized, making it difficult for illegal receivers to demodulate the original signal information by deciphering the timing information.

3. The method for multi-target secure communication of the pseudo-random time modulation four-dimensional antenna array according to claim 1, further characterized in that Since the useful signals transmitted in different directions after baseband modulation and time modulation are all at the same center frequency, a filter can be used to filter out the useless out-of-band signals, further ensuring the transmission security performance.

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