Phase modulation vortex electromagnetic wave radar foresight imaging method and device based on quasi-circular ring array, storage medium and electronic equipment

Abstract

The invention provides a phase modulation vortex electromagnetic wave radar foresight imaging method and device based on a quasi-circular ring array, a storage medium and electronic equipment. The method comprises the steps that the minimum array element number of vortex electromagnetic waves generated by using the quasi-circular ring array is determined according to the Nyquist sampling theorem; the electric field intensity of any point in the space is obtained by superposing the contribution of each array element, so that an antenna pattern of the quasi-circular ring array is derived; according to the magnitude of the main lobe energy of the synthetic antenna pattern, determining an optimal transmitting mode; the received single-mode signals are added, summed and stored for echo post-processing; performing phase modulation to obtain a complete echo signal; and finally, performing phase compensation and imaging. According to the method, the main lobe gain of vortex electromagnetic waves generated by the quasi-circular ring array is improved. The main lobe gain of an equivalent antenna pattern based on phase modulation is improved, and the side lobe is reduced. According to the two points, the imaging performance is improved in the low signal-to-noise ratio environment, the good anti-noise performance is achieved, and the azimuth resolution is improved to a certain degree.

Description

Technical Field

[0001] The present application relates to the technical field of signal processing, and particularly relates to a forward-looking imaging method, device, storage medium, and electronic device of a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array. Background Art

[0002] Radar imaging, as a means of obtaining information all-weather, all-day, and at a long distance, has become a key technology that countries are striving to develop. As a type of radar imaging, forward-looking radar plays an irreplaceable role in applications such as target detection, aircraft landing, missile guidance, and complex terrain mapping. Generally, the imaging resolution is mainly characterized by two dimensions: range and azimuth angle. The range dimension is compressed by transmitting a linear frequency modulation signal and applying a matched filtering technique. However, improving the azimuth resolution is challenging because it is limited by the antenna aperture. Existing high-resolution radar imaging techniques, such as synthetic aperture radar and Doppler beam sharpening, rely on the Doppler bandwidth and all produce blind spots in the forward-looking region. A real aperture radar uses the radar beam to scan the forward detection region, accumulates the echoes in each azimuth, and then forms an image. However, its azimuth resolution is limited and no longer meets the growing demand for higher radar forward-looking resolution. Therefore, it is necessary to develop a new radar system to solve this problem.

[0003] According to classical electromagnetic theory, it is known that electromagnetic waves carry momentum and angular momentum. Angular momentum can be further decomposed into spin angular momentum and orbital angular momentum. Electromagnetic waves carrying orbital angular momentum are called vortex electromagnetic waves, and their mathematical representation usually includes a phase term The phase of the vortex electromagnetic wave varies linearly along the azimuth angle in the XOY plane, and the rate of change l represents the mode number. Research shows that the mode number l of the vortex electromagnetic wave has infinity and orthogonality. Therefore, the vortex electromagnetic wave provides a new degree of freedom for information modulation. Since the phase wavefront of the vortex beam is helically distributed in space, the target irradiated by the vortex electromagnetic wave experiences different phases in each azimuth angle region. In contrast, this characteristic does not exist in plane electromagnetic waves. This unique characteristic provides a basis for the application of vortex electromagnetic waves in forward-looking radar systems. The advantage of the vortex electromagnetic wave lies in the Fourier dual relationship between the orbital angular momentum and the azimuth angle, which enables imaging between the radar and the target without lateral movement. This theoretically allows the azimuth resolution to increase as the modal range increases. Summary of the Invention

[0004] The purpose of the present application is to provide a forward-looking imaging method, device, storage medium, and electronic device of a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array to solve or alleviate the problems existing in the above-mentioned prior art.

[0005] To achieve the above purpose, the present application provides the following technical solutions:

[0006] This application provides a forward-looking imaging method for a phase modulation vortex electromagnetic wave radar based on a quasi-circular array, including: Step S101, determining the minimum number of array elements for generating vortex electromagnetic waves using a quasi-circular array according to the Nyquist sampling theorem; Step S102, obtaining the electric field strength at any point in space by superimposing the contributions of each array element, thereby deriving the antenna pattern of the quasi-circular array; Step S103, determining the optimal transmission mode according to the main lobe energy magnitude of the synthesized antenna pattern; Step S104, adding and summing the received single-mode signals and saving them for echo post-processing; Step S105, performing phase modulation to obtain a complete echo signal. Step S106, imaging after phase compensation of the echo.

[0007] Preferably, in Step S101, according to the Berry phase theory, in order to ensure the stability of the mode and maintain the total non-positive vortex intensity, the aperture angle β between adjacent units and the number of array elements M in the partial aperture quasi-circular array must satisfy the following relationship

[0008]

[0009] Preferably, in Step S102, in order to generate a vortex electromagnetic wave with a modulus of l, a gradually increasing phase is applied to each unit where m = 1, 2,..., M. Assuming that the quasi-circular array is composed of dipole antennas, then for any point in space, the electric field strength is given by the following formula:

[0010]

[0011] where j is the current density vector of the dipole antenna, μ0 is the magnetic permeability of free space, ω is the angular frequency of the electric field, k is the wave number, given by k = 2π / λ, where λ is the wavelength.

[0012] Using the infinitesimal dipole approximation, the amplitude is approximately |r - r m | ≈ r, and the phase is approximately: When M approaches infinity, that is, when there are infinitely many units along the partial circular arc, the electric field strength can be expressed in integral form

[0013]

[0014] Subsequently, for convenience, the constant is replaced by C. Using the Jacobi-Anger expansion, the electric field strength is expressed as a Bessel function series

[0015]

[0016] where v represents the harmonics of other modes generated after expansion. This integral has two cases

[0017]

[0018] Then the electric field generated by the partial-aperture quasi-circular array at any point in the far field can be expressed as:

[0019]

[0020] When the integration interval is γ = 2π, it degenerates to

[0021]

[0022] Preferably, in step S103, according to the main lobe energy of the synthesized antenna pattern, the optimal transmission mode l is determined. To improve the imaging resolution, a higher l value can be selected, but at the same time, it is necessary to ensure that the system can work stably in a low signal-to-noise ratio environment.

[0023] Preferably, in step S104, in free space represents an ideal point target located within the imaging region. The echo received by the m-th element is given by:

[0024]

[0025] where A p is the backscattering coefficient of the scattering point P, n is Gaussian white noise with a mean of 0 and a variance of σ 2 , w r (r) represents the envelope in the range direction, expressed as

[0026]

[0027] where K r represents the chirp rate, t is the range time, r is the distance to the target, c is the speed of light, f c is the carrier frequency;

[0028] Preferably, in step S105, in order to obtain the result of the phase-modulated echo signal, first, the signals received by the M array elements must be summed and stored. Then, different phases are modulated onto the signals to generate signals with different modes. The signal after summing the M elements is expressed as

[0029]

[0030] To obtain the signal for a specific mode, a specific phase modulation must be applied to the received signal. Therefore, the modulated signal can be expressed as:

[0031]

[0032] S r (l,t) = A0C 2 ·[Green(l,M)·Green(l′,M)]w r (r) + n

[0033] Based on the electric field results derived in step S102, the modulation signal can be expressed as:

[0034]

[0035] Preferably, in step S106, in the range direction, since a chirp signal is transmitted, range information can be obtained by down-conversion and by constructing a corresponding matched filter function for matched filtering operation

[0036]

[0037] where B w is the bandwidth of the signal.

[0038] From the above derivation, it can be concluded that the echoes processed by the proposed method still maintain the orthogonality between different OAM modes and maintain a good phase relationship. In other words, the azimuth information of the target can be directly obtained by performing a Fourier transform along the mode dimension. Therefore, the azimuth point spread function can be expressed as:

[0039]

[0040] From the above equation, based on the properties of the Fourier transform, it can be seen that a direct Fourier transform will result in false peaks, which will seriously affect the imaging performance. To alleviate this problem, phase compensation must first be applied to the echoes. Based on the analysis, it is concluded that since the harmonic amplitudes in the vortex electromagnetic waves generated by the quasi-circular array are very small, the signal can be approximated as containing only one dominant mode. Therefore, compensation is only required for the dominant mode, and the compensation function h(l + l′) of the signal can be written as:

[0041]

[0042] The compensated signal can be expressed as:

[0043]

[0044] The embodiments of the present application further provide a method and device for forward-looking imaging of a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array. The method includes determining the minimum number of array elements for generating vortex electromagnetic waves using a quasi-circular array; deriving the antenna pattern of the quasi-circular array; determining the transmission mode; receiving single-mode signals using the quasi-circular array; summing and storing the signals received by each array element, and performing phase modulation to obtain the corresponding mode; and performing phase compensation and imaging.

[0045] The embodiments of the present application further provide a computer-readable storage medium, on which a computer program is stored, and the program is the method for forward-looking imaging of a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array as described in any one of the above.

[0046] The embodiments of the present application further provide an electronic device, including: a memory, a processor, and a program stored in the memory and executable on the processor, and when the processor executes the program, it implements the method for forward-looking imaging of a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array as described in any one of the above.

[0047] Beneficial effects:

[0048] This application provides a method and device for forward-looking imaging of a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array. The method includes: determining the minimum number of array elements for generating vortex electromagnetic waves using a quasi-circular array; deriving the antenna pattern of the quasi-circular array; determining the transmission mode; receiving single-mode signals using the quasi-circular array; summing and storing the signals received by each array element, and performing phase modulation to obtain the corresponding mode; finally, performing phase compensation and imaging. Through this method, the main lobe gain of the vortex electromagnetic wave generated by the quasi-circular array is increased. The main lobe gain of the equivalent antenna pattern using phase modulation is increased, and the side lobes are reduced. Combining the above two points, this method improves the imaging performance and has good anti-noise performance in a low signal-to-noise ratio environment, and to a certain extent, improves the azimuth resolution. Description of the Drawings

[0049] The specification drawings forming a part of the present application are used to provide a further understanding of the present application. The schematic embodiments of the present application and their descriptions are used to explain the present application and do not constitute an improper limitation to the present application. Among them:

[0050] Figure 1 It is a flowchart of a method for forward-looking imaging of a single-pulse phase-modulated vortex electromagnetic wave radar according to some embodiments of the present application;

[0051] Figure 2 It is a forward-looking radar model of a quasi-circular array;

[0052] Figure 3 It is the OAM mode spectrum of the vortex electromagnetic wave generated by the quasi-circular array;

[0053] Figure 4 Effect of phase modulation on antenna pattern

[0054] Figure 5 Imaging result diagrams under different signal-to-noise ratios

[0055] Figure 6 Unit configuration diagram according to the present application Detailed implementation manners

[0056] The present application will be described in detail below with reference to the drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application rather than limiting the present application. In fact, those skilled in the art will appreciate that modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, features shown or described as part of one embodiment can be used in another embodiment to yield yet another embodiment. Accordingly, it is intended that the present application cover such modifications and variations that come within the scope of the appended claims and their equivalents.

[0057] Exemplary method

[0058] As Figure 1 shown, the forward-looking imaging method of the phase-modulated vortex electromagnetic wave radar based on a quasi-circular array includes:

[0059] In step S101, according to the Berry phase theory, in order to ensure the stability of the mode and maintain the total non-positive vortex intensity, the aperture angle β between adjacent units and the number of array elements M in the partial-aperture quasi-circular array must satisfy the following relationship

[0060]

[0061] In step S102, in order to generate a vortex electromagnetic wave with a modulus of l, a gradually increasing phase is applied to each unit where m = 1, 2,..., M. Assuming that the quasi-circular array is composed of dipole antennas, the electric field intensity at any point in space is given by the following formula:

[0062]

[0063] where j is the current density vector of the dipole antenna, μ0 is the magnetic permeability of free space, ω is the angular frequency of the electric field, k is the wave number, given by k = 2π / λ, where λ is the wavelength.

[0064] Using the infinitesimal dipole approximation, the amplitude is approximately |r - r m | ≈ r, and the phase is approximately: When M approaches infinity, that is, when there are infinitely many units along the partial circular arc, the electric field intensity can be expressed in integral form

[0065]

[0066] Subsequently, for convenience, the constant is replaced by C. Using the Jacobi-Anger expansion, the electric field strength is expressed as a series of Bessel functions

[0067]

[0068] where v represents the harmonics of other modes generated after expansion. There are two cases for this integral.

[0069]

[0070] Then, the electric field generated by the partial-aperture quasi-circular array at any point in the far field can be expressed as:

[0071]

[0072] When the integration interval is γ = 2π, it degenerates to

[0073]

[0074] In step S103, according to the main lobe energy of the synthesized antenna pattern, the optimal transmission mode l is determined. To improve the imaging resolution, a higher l value can be selected, but at the same time, it is necessary to ensure that the system can work stably in a low signal-to-noise ratio environment.

[0075] In step S104, in free space represents an ideal point target located within the imaging region. The echo received by the m-th element is given by:

[0076]

[0077] where A p is the backscattering coefficient of the scattering point P, n is Gaussian white noise with a mean of 0 and a variance of σ 2 , and w r (r) represents the envelope in the range direction, expressed as

[0078]

[0079] where K r represents the chirp rate, t is the range time, r is the distance to the target, c is the speed of light, and f c is the carrier frequency;

[0080] In step S105, in order to obtain the result of the echo signal after single-pulse phase modulation, first, the signals received by M array elements must be summed and stored. Then, different phases are modulated onto the signals to generate signals with different patterns. The signal after summing the M elements is denoted as

[0081]

[0082] To obtain the signal for a specific pattern, a specific phase modulation must be applied to the received signal. Thus, the modulated signal can be expressed as:

[0083]

[0084] S r (l,t) = A0C 2 ·[Green(l,M)·Green(l′,M)]w r (r) + n

[0085] Based on the electric field result derived in step S102, the modulated signal can be expressed as:

[0086]

[0087] In step S106, in the range direction, since a linear frequency modulation (LFM) signal is transmitted, range information can be obtained by down-conversion and by constructing the corresponding matched filter function for the matched filtering operation

[0088]

[0089] where B w is the bandwidth of the signal.

[0090] From the above derivation, it can be concluded that the echo processed by the proposed method still maintains the orthogonality between different OAM modes and maintains a good phase relationship. In other words, the azimuth information of the target can be directly obtained by performing a Fourier transform along the mode dimension. Thus, the azimuth angle point spread function (PSF) can be expressed as

[0091]

[0092] From the above equation, based on the properties of the Fourier transform, it can be seen that a direct Fourier transform will result in false peaks, which will seriously affect the imaging performance. To alleviate this problem, phase compensation must first be applied to the echo. Based on the analysis, it is concluded that since the harmonic amplitudes in the vortex electromagnetic wave generated by the quasi-circular array are very small, the signal can be approximated as containing only one dominant mode. Therefore, compensation is only required for the dominant mode, and the compensation function h(l + l′) of the signal can be written as

[0093]

[0094] The compensated signal can be expressed as

[0095]

[0096] Figure 2 It shows the geometric configuration of the quasi-circular array in the XOY plane, where M elements are uniformly arranged along a partial circular arc with a radius of a.

[0097] Figure 3 It shows the OAM spectrum of the vortex electromagnetic wave generated by the quasi-circular array, which has three-quarters of a circular arc and 16 elements in the full aperture. Among them, (a) l = 2, (b) l = 3, (c) l = 4, (d) l = 5. From Figure 3 it can be seen that for small modes, the harmonics have much lower intensities than the main mode.

[0098] Figure 4 Compared with the pattern of the uniform circular array, the synthesized antenna radiation pattern has a narrower main lobe. According to the Rayleigh criterion, after single-pulse phase modulation of the echo and then signal processing, the resolution of the focused image will be improved, where (a) l = 2, (b) l = 3, (c) l = 4, (d) l = 5.

[0099] Figure 5 It shows the imaging result diagrams under different signal-to-noise ratios, where (a) SNR = 10dB, (b) SNR = 5dB, (c) SNR = 0dB, (d) SNR = -5dB, (e) SNR = -10dB, (e) SNR = -15dB.

[0100] Exemplary system

[0101] Figure 6 This application embodiment also provides a method, device and system for forward-looking imaging of a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array, including: a minimum element number calculation unit configured to determine the minimum element number for generating a vortex electromagnetic wave using a quasi-circular array according to the Nyquist sampling theorem; an antenna pattern calculation unit configured to obtain the electric field strength at any point in space by superimposing the contributions of each element, thereby deriving the antenna pattern of the quasi-circular array; an optimal transmission mode calculation unit configured to determine the optimal transmission mode according to the main lobe energy magnitude of the synthesized antenna pattern; a unit for adding and summing and saving the received single-mode signals, configured to add and sum and save the received single-mode signals for echo post-processing; a phase modulation unit configured to perform phase modulation to obtain a complete echo signal; and a phase compensation and imaging unit configured to perform phase compensation on the echo and then image.

[0102] The quasi-circular array provided in the embodiments of the present application generates a vortex electromagnetic wave with a concentrated main lobe by using this array, and proposes a post-processing system based on phase modulation that can implement any of the above-mentioned method steps and processes of the phase modulation vortex electromagnetic wave radar forward-looking imaging method and device based on the quasi-circular array, and achieve the same technical effects, which will not be elaborated here one by one.

[0103] Exemplary device

[0104] The present application provides an electronic device, including a storage medium and a processor. The processor is suitable for executing each program; the memory is used for storing multiple programs; when the memory executes the program on the processor, the above-mentioned phase modulation vortex electromagnetic wave radar forward-looking imaging method based on the quasi-circular array is implemented.

[0105] Since the phase modulation vortex electromagnetic wave radar forward-looking imaging method and device based on the quasi-circular array have been introduced in detail in the specific implementation method examples, no further detailed description will be given here.

[0106] Among them, the processor includes a central processing unit (Central Processing Unit, abbreviated as CPU), a network processor (Network Processor, abbreviated as NP), etc., and can also be a digital signal processor, an application-specific integrated circuit, a field-programmable gate array, or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. It can implement or execute the various methods, steps, and logic block diagrams disclosed in the embodiments of the present application. The general-purpose processor can be a microprocessor or the processor can also be any conventional processor, etc.

[0107] Specifically, the processor can be configured as follows: the input system inputs the electric field amplitude and phase of the vortex electromagnetic wave measured in free space; determines the minimum number of array elements for generating the vortex electromagnetic wave using the quasi-circular array according to the Nyquist sampling theorem; obtains the electric field intensity at any point in space by superimposing the contributions of each array element, thereby deriving the antenna pattern of the quasi-circular array; determines the optimal transmission mode according to the main lobe energy size of the synthesized antenna pattern; adds and sums the received single-mode signals and saves them for echo post-processing; performs phase modulation to obtain a complete echo signal; and performs phase compensation on the echo for imaging.

[0108] It should be noted that according to the needs of implementation, each component / step described in the embodiments of the present application can be split into more components / steps, or two or more components / steps or partial operations of the components / steps can be combined into new components / steps to achieve the purpose of the embodiments of the present application.

[0109] The method according to the embodiments of the present application can be implemented in hardware, firmware, or be implemented as software or computer code that can be stored in a recording medium (such as a CD ROM, RAM, floppy disk, hard disk, or magneto-optical disk), or be implemented as computer code originally stored in a remote recording medium or a non-transitory machine storage medium and to be downloaded through a network and stored in a local recording medium, so that the method described herein can be stored in such software processing on a recording medium using a general-purpose computer, a dedicated processor, or programmable or dedicated hardware (such as an ASIC or an FPGA). It can be understood that a computer, a processor, a microprocessor controller, or programmable hardware includes a storage component (such as RAM, ROM, flash memory, etc.) that can store or receive software or computer code, and when the software or computer code is accessed and executed by the computer, the processor, or the hardware, the method for single-track synthetic aperture radar jammer localization described herein is implemented. In addition, when a general-purpose computer accesses the code for implementing the method shown herein, the execution of the code converts the general-purpose computer into a dedicated computer for executing the method shown herein.

[0110] Those of ordinary skill in the art can realize that the units and method steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, or by a combination of computer software and electronic hardware. Whether these functions are executed in a hardware or software manner depends on the specific application of the technical solution and the involved constraints. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the embodiments of the present application.

[0111] It should be noted that the embodiments in this specification are all described in a progressive manner. The same or similar parts between the embodiments can be referred to each other, and each embodiment focuses on the differences from other embodiments. In particular, for the device and system embodiments, since they are basically similar to the method embodiments, they are described relatively simply, and the relevant parts can be referred to the partial description of the method embodiments.

[0112] The device and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separated, and the components described as units may or may not be physical units, that is, they may be located in one place, or may be distributed to multiple network units. Some or all of the modules can be selected according to actual needs to achieve the purpose of the solution of this embodiment. Those of ordinary skill in the art can understand and implement it without creative efforts.

[0113] The above are only the preferred embodiments of the present application and are not intended to limit the present application. For those skilled in the art, various changes and modifications can be made to the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included within the protection scope of the present application.

Claims

1. A forward-looking imaging method for a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array, characterized in that, It includes the following steps: Step S101: Determine the minimum number of array elements for generating vortex electromagnetic waves using a quasi-circular array according to the Nyquist sampling theorem; Step S102: Obtain the electric field strength at any point in space by superimposing the contributions of each array element, thereby deriving the antenna pattern of the quasi-circular array; Step S103: Determine the optimal transmission mode according to the main lobe energy magnitude of the synthesized antenna pattern; Step S104: Add and sum the received single-mode signals and save them for echo post-processing; Step S105: Perform phase modulation to obtain a complete echo signal; Step S106: Perform phase compensation and imaging.

2. The method for forward-looking imaging of a phase modulation vortex electromagnetic wave radar based on a quasi-circular array according to claim 1, wherein In step S101, the number of array elements is solved through the following steps: According to the Berry phase theory, the aperture angle β between adjacent units in a partial-aperture quasi-circular array and the number of array elements M must satisfy the following relationship: Thereby, it can ensure the stability of the mode and maintain the total non-positive vortex intensity.

3. The method for forward-looking imaging of a phase modulation vortex electromagnetic wave radar based on a quasi-circular array according to claim 1, wherein The electric field strength at any point in step S102 includes the following steps: To generate a vortex electromagnetic wave with a modulus of l, a gradually increasing phase is applied to each unit. where m = 1, 2,..., M. Assuming that the quasi-circular array is composed of dipole antennas, then at any point in space, the electric field strength is given by the following formula: Where j is the current density vector of the dipole antenna, μ0 is the magnetic permeability of free space, ω is the angular frequency of the electric field, k is the wave number, given by k = 2π / λ, where λ is the wavelength, and i is the imaginary unit; Using the infinitesimal dipole approximation, the amplitude is approximately |r - r m | ≈ r, and the phase is approximately: When M approaches infinity, that is, when there are an infinite number of elements along a partial circular arc, the electric field strength can be expressed in integral form Subsequently, the constant is replaced by C; using the Jacobi-Anger expansion, the electric field strength is expressed as a series of Bessel functions where v represents other modes generated after expansion, J v represents the v-th order of the first kind of Bessel function; there are two cases for this integral Then, the electric field generated by the partial-aperture quasi-circular array at any point in the far field can be expressed as: where J l denotes the l-th order of the first kind of Bessel function; When the integration interval is γ = 2π, it degenerates to 4. The method for forward-looking imaging of a phase modulation vortex electromagnetic wave radar based on a quasi-circular array according to claim 1, wherein In step S103, according to the main lobe energy magnitude of the synthesized antenna pattern, determine the optimal transmission mode l.

5. The forward-looking imaging method of the phase modulation vortex electromagnetic wave radar based on a quasi-circular array according to claim 1, characterized in that In step S104, in order to obtain the result of the echo signal after phase modulation, first, the signals received by M array elements must be summed and stored; then, different phases are modulated onto the signals to generate signals with different modes; the signal after summing the M elements is denoted as When processing the echo, its expression is as follows: In free space, represents an ideal point target located within the imaging region; the echo received by the m-th element is given by the following formula: Among them, A p is the backscattering coefficient of the scattering point P, n is Gaussian white noise with a mean of 0 and a variance of σ 2 , and w r (r) represents the envelope in the range direction and is expressed as Among them, K r represents the chirp rate, t is the range time, r is the distance to the target, c is the speed of light, and f c is the carrier frequency.

6. The forward-looking imaging method of a phase modulation vortex electromagnetic wave radar based on a quasi-circular array according to claim 1, wherein When performing phase modulation in step S105, in order to obtain a signal for a specific mode, a specific phase modulation must be applied to the received signal; thus, the modulated signal can be expressed as: applied to the received signal; thus, the modulated signal can be expressed as: S r (l,t) = A0C 2 ·[Green(l,M)·Green(l ′ ,M)]w r (r) + n Based on the electric field result derived in step S102, the modulated signal can be expressed as:

7. The method for forward-looking imaging of a phase modulation vortex electromagnetic wave radar based on a quasi-circular array according to claim 1, wherein In step S106, it specifically includes the following steps: In the range direction, since a chirp signal is transmitted, range information is obtained through down-conversion and by constructing a corresponding matched filter function for matched filtering operation Among them, B w is the bandwidth of the signal; The azimuth point spread function can be expressed as Since the harmonic amplitude in the vortex electromagnetic wave generated by the quasi-circular array is very small, the signal can be approximated as only containing one main mode; therefore, compensation is only required for the dominant mode, and the compensation function h(l + l′) of the signal can be written as The compensated signal can be expressed as 8. A forward-looking imaging device for a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array, characterized in that, It includes: A minimum number of array elements calculation unit, which determines the minimum number of array elements for generating vortex electromagnetic waves using a quasi-circular array according to the Nyquist sampling theorem; An antenna pattern calculation unit, which obtains the electric field strength at any point in space by superimposing the contributions of each array element, thereby deriving the antenna pattern of the quasi-circular array; An optimal transmission mode calculation unit, which determines the optimal transmission mode according to the main lobe energy magnitude of the synthesized antenna pattern; An echo processing unit, which adds and sums the received single-mode signals and saves them for echo post-processing; A phase modulation unit, which performs phase modulation to obtain a complete echo signal; A phase compensation imaging unit, which performs phase compensation on the echo and then images.

9. A storage medium in which multiple programs are stored, characterized in that, The program application is loaded and executed by a processor to implement the method for forward-looking imaging of a phase-modulated vortex electromagnetic wave radar based on a quasi-circular array according to any one of claims 1-7.

10. An electronic device, comprising a storage medium and a processor; the processor is adapted to execute each program; the memory is used to store multiple programs; characterized in that, When the memory executes the program on the processor, it implements the forward-looking imaging method of the phase modulation vortex electromagnetic wave radar based on the quasi-circular array according to any one of claims 1-7.

Images