WO2023060862A1 - Cylindrical scanning microwave imaging method - Google Patents

Abstract

A cylindrical scanning microwave imaging method, which relates to the technical fields of optical imaging, microwave imaging, radar detection, sonar, ultrasound imaging, and target detection, imaging recognition and wireless communications based on media such as sound, light and electricity; and the application of the method in all of the fields. By means of using the method, ultrafast scanning of a target can be realized by first using a passive imaging technique; and when a suspect object is found, details of the object can be observed in detail by using an active imaging technique, and the two imaging methods can share one signal processing system, thereby greatly reducing the hardware costs, improving the imaging speed, and providing great convenience for practical application. In addition, the method is also suitable for an imaging system, such as a rotary-table imaging system, in which an antenna is fixed and a target rotates. The method also has the advantages of good compatibility, a small amount of computation, good imaging effect and a wide application range.

Description

Cylindrical Scanning Microwave Imaging Method technical field

The invention relates to the technical fields of optical imaging, microwave imaging, radar detection, sonar, ultrasonic imaging, and target detection, imaging recognition, and wireless communication based on media such as sound, light, and electricity, and specifically relates to a cylindrical scanning microwave imaging method and its application in the above applications in various fields.

Background technique

Digital holographic imaging technology evolved from laser holographic imaging technology has high imaging resolution and is currently one of the preferred technologies for millimeter-wave active imaging, and related products have been promoted and applied in different fields at home and abroad.

However, traditional digital holographic imaging technology still has many defects and deficiencies, mainly including:

1) Large amount of computation, high cost, and slow imaging speed

The existing digital holographic imaging technology requires two operations of fast Fourier transform (FFT) and inverse fast Fourier transform (IFFT) in sequence ("FFT-phase compensation-IFFT" operation), and the amount of calculation is huge. The configuration requirements of the hardware environment and computing resources are high, so the hardware price and operating cost are high. In addition, the imaging speed is slow because of the need to perform FFT and IFFT operations twice in sequence.

2) It can only be used for near-field imaging, not for long-distance imaging

In the existing digital holographic imaging technology, when the target distance is relatively long, the phase compensation is negligible. At this time, it is equivalent to performing "FFT-IFFT" operation, which will cause imaging distortion or even imaging failure.

In addition, as a new expansion of holographic imaging technology, cylindrical scanning imaging has stereoscopic imaging capabilities, and can quickly realize circular scanning and omnidirectional imaging of targets. Compared with the planar linear scanning system, cylindrical scanning imaging is more widely used. However, although the existing holographic imaging technology can also realize cylindrical scanning imaging, the imaging method is often very complicated, the hardware cost is high, the imaging speed is slow, and different technologies are required for passive imaging and active imaging, and the mutual compatibility is poor. , which increases the difficulty for actual use, and most of the existing methods are not suitable for large-angle imaging application scenarios. When the target deviates from the normal direction of the array at a large angle, the imaging effect becomes poor. At this time, the resolution is low and satisfactory Therefore, it is of great application value to develop a cylindrical scanning imaging method with good compatibility, excellent imaging effect, wider application range and faster imaging speed.

Contents of the invention

In order to overcome the above defects and shortcomings of traditional digital holographic active imaging, especially cylindrical scanning imaging technology, the present invention provides a set of solutions.

As shown in Figure 1, the linear array is used to scan around the target P, and the echo distribution on the scanned cylindrical array is recorded sequentially, and the omnidirectional imaging of the target can be realized by imaging the data.

The coordinate system of the imaging system is established, P is the target, Q is the image of the target, the synthesized local antenna front is located on the plane of z=0, and the mark X represents the transmitting and receiving antenna unit.

Let the radius of the scanning cylinder be ρ,

Indicates the angle at which the array unit deviates from the array center in the cylindrical coordinate system. Use (x, y, z) to represent the coordinates of the array unit. As the scanning position changes, the coordinates of the array unit have the following calculation formula:

The propagation phase shift introduced when the signal propagates through one-way R ₁ and R ₂ is:

Some of the variables useful for imaging focus are:

Among them: φ ₁ is the propagation phase shift from the scattering source P to the array unit, φ ₂ is the propagation phase shift from the array unit to the image point Q,

is the wave number, U is the object distance, V is the image distance, (ζ,ξ) is the coordinate of the scattering source, (x,y,z) is the coordinate of the array unit, (δ,σ) is the coordinate of the image point.

Among them, with the cylindrical scanning, the synthesized antenna array is equivalent to a lens with a focal length of F, then the effective phase shift of the lens unit is:

Among them: φ _L is the lens phase shift of the array unit, and F is the focal length.

In passive imaging, the antenna unit does not transmit the detection signal, but only receives the scattered signal of the target. After the antenna receives the scattered signal of the target, it performs secondary scattering in the form of spherical waves, and passes through different transmission paths R ₁ and R ₂ The field strength arriving at the image plane after being phase-shifted with the lens unit is:

During holographic imaging, the signal is sent from the antenna unit and received by the antenna unit after being reflected by the target. The signal has experienced a two-way transmission with a distance of R ₁ , and the corresponding phase delay is 2φ ₁ . During imaging processing, both the phase shift of the lens unit and the _R2 propagation phase shift need to be processed in two ways: the transceiver antenna unit sequentially transmits detection signals, and after the signal reflected by the target P reaches the transceiver antenna unit, it is carried out in the form of a spherical wave For secondary scattering, the field strength reaching the image plane after two-way phase shift of different transmission paths R ₁ and R ₂ is:

Comparing the imaging formulas in the above two cases, by introducing the auxiliary selection parameter η, the above two formulas can be unified as follows:

Wherein, η=1 is suitable for passive imaging, and η=2 is suitable for active holographic imaging.

In actual imaging, only the following processing is required:

The target signal received by the antenna unit is E, and A is the amplitude weighting coefficient. After substituting the expressions of φ _L and φ ₂ to simplify:

in,

When the imaging conditions are met

, the above formula can be simplified to:

Use relational formula:

After integral transformation:

Discretize the above formula:

Among them, the symbol exp represents an exponential function with Euler's constant e as the base. make

y _n =y ₀ +nΔ _y , put into the above formula and simplify:

in,

The coefficients on the right side of the above formula satisfy

It reflects the spatial fluctuation characteristics of the image field and basically has no effect on imaging and can be ignored. Regardless of the influence of coefficients, the summation operation can be quickly solved by two-dimensional IFFT, and the calculation formula of the image field is:

Does not take into account the operation of the core

The calculation formula can be further simplified:

Wherein, IFFT represents a two-dimensional or three-dimensional IFFT operation. The value ranges of ω _δ and ω _σ corresponding to the IFFT calculation results are: ω _δ ∈ [0,2π], ω _σ ∈ [0,2π], after the fftshift operation, the value ranges of ω _δ and ω _σ are transformed into: ω _δ ∈ [-π, π], ω _σ ∈ [-π, π], the image at this time is the image that conforms to the actual distribution, and has a good linear mapping relationship with the source field.

Combined with the array antenna theory, there are ω _δ = ηkΔ _x sin θ _δ , ω _σ = ηkΔ _y sin θ _σ .

Since the repetition period of the discrete FFT transform is 2π, if it is required that no image aliasing occurs, then there should be

|ω|≤π;

Let the cell spacing be Δ, so that:

Usually the effective range of θ is [-π/2,π/2], and the conditions to ensure that the above formula is always true are:

The non-aliasing condition of the cylindrical scanning half-air domain image is:

The array antenna theory is used to correct the scanning angle coordinates of the image point:

Our research shows that the matching formula

It can be further improved, and the imaging performance at large angles can be improved by replacing the object distance parameter U with the target slant distance R:

On the basis of the above understanding, the present invention provides a cylindrical scanning microwave imaging method, which is based on the principle of lens imaging, combined with electromagnetic field theory, according to the target signal received by the antenna array, weighted by the amplitude and phase of the unit signal, using high-efficiency Parallel algorithm to obtain the image field distribution corresponding to the target, the specific algorithm is as follows:

Among them: j is the imaginary number unit, e is Euler's constant,

is the image field distribution,

is the target signal received by the array unit, A _mn is the amplitude weighting coefficient of the array unit,

is the weighted value for the cylindrical scan amplitude,

is the focus phase weighting coefficient,

is the cylindrical scanning phase compensation coefficient,

is the scanning phase weighting coefficient, M is the number of array units in the x direction, N is the number of array units in the y direction, (x _m , y _n ) is the coordinate of the array unit, (δ, σ) is the coordinate of the image point, V is Image distance, that is, the distance from the imaging plane to the array plane, η is the object selectivity parameter, select different values according to the characteristics of the imaging system, m and n are the serial numbers of the array unit in the x direction and the y direction, respectively,

is the wave number, λ is the wavelength, and the symbol ∑ represents the summation operation.

Further, the method of the present invention is applicable to different imaging systems by selecting different parameter η values, specifically:

When η=1 is selected, it is suitable for passive imaging system and semi-active imaging system;

When η=2, it is suitable for active holographic imaging system.

Further, the method of the present invention comprises the following steps:

Step 1: performing amplitude weighting on the array unit signal to reduce the side lobe level;

Step 2: Perform focus phase weighting on the array unit signals to achieve imaging focus;

Step 3: Perform cylindrical scanning amplitude compensation and phase compensation on the array unit signal to improve imaging performance;

Step 4: Perform beam scanning phase weighting on the array unit signals to adjust the central viewing angle direction of the imaging system;

Step 5: Perform fast imaging processing on array unit signals by using efficient parallel algorithms;

Step 6: Calculate the coordinates of the image field, and perform coordinate inversion on the image field to obtain the position of the real target.

Further, the method of amplitude weighting in step 1 of the method of the present invention includes but not limited to uniform distribution, cosine weighting, Hamming window, Taylor distribution, Chebyshev distribution and mixed weighting methods.

Further, in step 2 of the method of the present invention, focus phase weighting is performed on the array unit signals to achieve imaging focus, wherein:

The focus phase calculation formula for auto focus phase weighting is:

Among them, R is the target slant distance, that is, the distance from the target to the center of the array;

The focus phase calculation formula for zoom or fixed focus phase weighting is:

Among them, F is the focal length, V is the image distance, that is, the distance from the imaging plane to the plane where the receiving array is located, and F<U, F<V.

Further, in the third step of the method of the present invention, the array unit signal is subjected to cylindrical scanning amplitude compensation and phase compensation to improve imaging performance, wherein:

The calculation formula of cylindrical scan amplitude compensation is:

in,

Indicates the angle at which the array unit deviates from the center of the array in the polar coordinate system, requiring

When the range of the intercepted synthetic array is small, that is, the equivalent array aperture is small, directly select

to simplify the calculation process.

Further, in the third step of the method of the present invention, the array unit signal is subjected to cylindrical scanning amplitude compensation and phase compensation to improve imaging performance, wherein:

The calculation formula of cylindrical scanning phase compensation is:

Among them, ρ is the radius of the scanning cylinder,

Indicates the angle at which the array unit deviates from the array center in the polar coordinate system.

As a preference, in the uniform-velocity cylindrical scanning imaging system, the calculation formula of the above-mentioned cylindrical scanning phase compensation can be improved as:

Among them, Ω is the angular frequency of cylindrical scanning, and t _mn is the scanning time when the center of the array is scanned to zero.

Further, the scanning phase weighting described in step 4 of the method of the present invention adjusts the central viewing angle direction of the imaging system, and the phase calculation formula of the scanning phase weighting is:

in:

Respectively, the phase difference between adjacent elements of the array in the x and y directions, and their calculation formulas are:

in:

is the scanning step angle of cylindrical scanning, Δ _y is the array element spacing in the y direction, θ _ζ and θ _ξ are the scanning angle coordinates in the x and y directions when the central viewing angle direction points to the source coordinates (ζ, ξ), and the calculation formula They are:

Among them: U is the object distance, that is, the distance from the plane where the target is located to the array plane.

Further, the high-efficiency parallel algorithm described in step five of the method of the present invention is used to perform fast imaging processing on the array unit signal; the high-efficiency parallel algorithm includes two-dimensional or three-dimensional FFT, IFFT, non-uniform FFT, and sparse FFT, and the calculation formula is :

where: symbol

represents an efficient parallel algorithm function,

is the target signal received by the array unit, A is the amplitude weighting coefficient of the array unit, A _C is the weighting value of the cylindrical scanning amplitude, φ _F is the focusing phase weighting coefficient, φ _C is the cylindrical scanning phase compensation coefficient, and φ _S is the scanning phase weighting coefficient ;

The value ranges of ω _δ and ω _σ corresponding to the above image field calculation results are: ω _δ ∈ [0,2π], ω _σ ∈ [0,2π], and after performing fftshift operation, the value ranges of ω _δ and ω _σ are transformed into : ω _δ ∈ [-π, π], ω _σ ∈ [-π, π], the image at this time conforms to the image of the actual distribution:

Further, step six of the method of the present invention includes: performing coordinate calculation on the image field obtained by the efficient parallel algorithm, and performing coordinate inversion on the image field to obtain the position of the real target; wherein:

For the efficient parallel algorithm of the IFFT class, the calculation formula of the image field scanning angle coordinates is:

For the efficient parallel algorithm of the FFT class, the calculation formula of the image field scanning angle coordinates is:

The formula for calculating the Cartesian coordinates of the image is:

δ = V tan θ _δ ,

σ = V tan θ _σ ;

The coordinate inversion calculation formula of the real target is:

Further, the scan step of setting the transceiver antenna in the method of the present invention satisfies:

to avoid image aliasing.

In addition, the method of the present invention is also applicable to imaging systems with fixed antennas and rotating targets, including ISAR imaging systems and turntable imaging systems; For angular frequency, replace the cylindrical scan radius with the distance from the antenna to the center of rotation.

At the same time, the present invention also relates to the application of the above method in the fields of optical imaging, microwave imaging, radar detection, sonar, ultrasonic imaging, sound, light, and electrical target detection, imaging recognition, and wireless communication.

In summary, the cylindrical scanning microwave imaging method of the present invention has the following advantages:

1) Created a fast imaging method suitable for cylindrical scanning

The present invention realizes a low-cost and fast cylindrical scanning imaging, and its calculation amount is much lower than that of the active holographic imaging system, which can save a lot of hardware resources and improve the imaging speed.

2) Established a unified imaging method compatible with passive imaging and active imaging

By adopting the method of the present invention, passive imaging technology can be used to realize ultra-fast scanning of the target first, and when a suspect object is found, active imaging technology can be used to observe the details of the object in detail, and the two imaging methods can share a set of signal processing systems, thereby The hardware cost is greatly reduced, the scanning speed is increased, and the practical application is greatly facilitated. At the same time, the method of the present invention is also applicable to imaging systems with fixed antennas and rotating targets, such as turntable imaging.

3) Further improve the imaging effect

In the present invention, in the phase compensation method, the target slant distance R is used to replace the object distance parameter U. Compared with the object distance parameter U, the parameter R is easier to obtain, and the imaging effect is better.

4) It is suitable for long-distance imaging and has a wider range of applications

In the present invention, when imaging at a long distance, the phase compensation is also negligible. At this time, it is equivalent to performing an IFFT operation to realize imaging of a long-distance target.

In addition, the method of the present invention has a good application prospect and can be widely used in the field of target detection and wireless communication technology using sound, light, electricity, etc. as the medium. When the detection medium is electromagnetic waves, the technology is applicable to microwave imaging, radar detection, Wireless communication, synthetic aperture radar, and inverse synthetic aperture radar; when the detection medium is sound waves and ultrasonic waves, this technology is applicable to sonar, ultrasonic imaging, and synthetic aperture sonar; when the detection medium is light, this technology is applicable to optical imaging, synthetic aperture optical imaging.

Description of drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following will briefly introduce the accompanying drawings that need to be used in the description of the embodiments of the present invention. Obviously, the following drawings are only some embodiments recorded in the present invention. Those skilled in the art can also obtain other drawings based on these drawings without any creative work.

Fig. 1 is a schematic diagram of the coordinate system of the imaging system of the imaging method of the present invention.

Fig. 2 is an algorithm block diagram of the imaging method of the present invention.

Fig. 3 is an imaging result diagram of passive imaging case 1 performed by the imaging method of the present invention.

Fig. 4 is an imaging result diagram of active holographic imaging case 2 performed by the imaging method of the present invention.

Detailed ways

In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution of the present invention will be clearly and completely described below in conjunction with specific embodiments and corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. The present invention can also be implemented or applied through other different specific implementation modes, and the details in this specification can also be based on different viewpoints Various modifications or changes may be made without departing from the spirit of the invention.

Simultaneously, it should be understood that the protection scope of the present invention is not limited to the following specific embodiments; protected range.

Embodiment 1: A cylindrical scanning microwave imaging method (see accompanying drawing 1-2), this method is based on the principle of lens imaging, combined with electromagnetic field theory, according to the target signal received by the antenna array, weighted by the amplitude and phase of the unit signal, using Efficient parallel algorithm to obtain the image field distribution corresponding to the target. The specific algorithm is as follows:

Among them: j is the imaginary number unit, e is Euler's constant,

is the image field distribution,

is the target signal received by the array unit, A _mn is the amplitude weighting coefficient of the array unit,

is the weighted value for the cylindrical scan amplitude,

is the focus phase weighting coefficient,

is the cylindrical scanning phase compensation coefficient,

is the scanning phase weighting coefficient, M is the number of array units in the x direction, N is the number of array units in the y direction, (x _m , y _n ) is the coordinate of the array unit, (δ, σ) is the coordinate of the image point, V is Image distance, that is, the distance from the imaging plane to the array plane, η is the object selectivity parameter, select different values according to the characteristics of the imaging system, m and n are the serial numbers of the array unit in the x direction and the y direction, respectively,

is the wave number, λ is the wavelength, and the symbol ∑ represents the summation operation.

Further, the method can be applied to different imaging systems by selecting different parameter η values: when η=1 is selected, it is applicable to passive imaging systems and semi-active imaging systems; when η=2 is selected, it is applicable to active holographic imaging systems .

Specifically, the imaging method includes the following steps:

Step 1: performing amplitude weighting on the array unit signal to reduce the side lobe level;

Amplitude weighting methods include, but are not limited to, uniform distribution, cosine weighting, Hamming window, Taylor distribution, Chebyshev distribution, and hybrid weighting methods.

Step 2: Perform focus phase weighting on the array unit signals to achieve imaging focus;

Among them: the focus phase calculation formula of auto focus phase weighting is:

Among them, R is the target slant distance, that is, the distance from the target to the center of the array;

The focus phase calculation formula for zoom or fixed focus phase weighting is:

Among them, F is the focal length, V is the image distance, that is, the distance from the imaging plane to the plane where the receiving array is located, and F<U, F<V.

Step 3: Perform cylindrical scanning amplitude compensation and phase compensation on the array unit signal to improve imaging performance;

The calculation formula of cylindrical scan amplitude compensation is:

in,

Indicates the angle at which the array unit deviates from the center of the array in the polar coordinate system, requiring

When the range of the intercepted synthetic array is small, that is, the equivalent array aperture is small, directly select

to simplify the calculation process.

The calculation formula of cylindrical scanning phase compensation is:

Among them, ρ is the radius of the scanning cylinder,

Indicates the angle at which the array unit deviates from the array center in the polar coordinate system.

In addition, in the uniform-velocity cylindrical scanning imaging system, the calculation formula of the above-mentioned cylindrical scanning phase compensation can be improved as:

Among them, Ω is the angular frequency of cylindrical scanning, and t _mn is the scanning time when the center of the array is scanned to zero.

Step 4: Perform beam scanning phase weighting on the array unit signals to adjust the central viewing angle direction of the imaging system;

The phase calculation formula of its scanning phase weighting is:

in:

Respectively, the phase difference between adjacent elements of the array in the x and y directions, and their calculation formulas are:

in:

is the scanning step angle of cylindrical scanning, Δ _y is the array element spacing in the y direction, θ _ζ and θ _ξ are the scanning angle coordinates in the x and y directions when the central viewing angle direction points to the source coordinates (ζ, ξ), and the calculation formula They are:

Among them: U is the object distance, that is, the distance from the plane where the target is located to the array plane.

Step 5: Perform fast imaging processing on array unit signals by using efficient parallel algorithms;

Efficient parallel algorithms include two-dimensional or three-dimensional FFT, IFFT, non-uniform FFT, and sparse FFT. The calculation formula is:

where: symbol

represents an efficient parallel algorithm function,

is the target signal received by the array unit, A is the amplitude weighting coefficient of the array unit, A _C is the weighting value of the cylindrical scanning amplitude, φ _F is the focusing phase weighting coefficient, φ _C is the cylindrical scanning phase compensation coefficient, and φ _S is the scanning phase weighting coefficient ;

The value ranges of ω _δ and ω _σ corresponding to the above image field calculation results are: ω _δ ∈ [0,2π], ω _σ ∈ [0,2π], and after performing fftshift operation, the value ranges of ω _δ and ω _σ are transformed into : ω _δ ∈ [-π, π], ω _σ ∈ [-π, π], the image at this time conforms to the image of the actual distribution:

Step 6: Calculate the coordinates of the image field, and perform coordinate inversion on the image field to obtain the position of the real target.

Among them: for the efficient parallel algorithm of the IFFT class, the calculation formula of the image field scanning angle coordinates is:

For the efficient parallel algorithm of the FFT class, the calculation formula of the image field scanning angle coordinates is:

The formula for calculating the Cartesian coordinates of the image is:

δ = V tan θ _δ ,

σ = V tan θ _σ ;

The coordinate inversion calculation formula of the real target is:

In addition, in this imaging method, the scanning step of setting the transmitting and receiving antenna satisfies:

to avoid image aliasing.

Moreover, this imaging method is also applicable to imaging systems with fixed antennas and rotating targets, including ISAR imaging systems and turntable imaging systems; For angular frequency, replace the cylindrical scan radius with the distance from the antenna to the center of rotation.

Embodiment 2: This imaging method (embodiment 1 method) is used for the effect verification experiment of passive imaging

Test conditions: the working frequency is 30GHz, the spacing between antenna elements is kept at λ/4 during scanning, the array size is 66*66, one target is located in the normal direction of the array, and the other two targets deviate from the normal direction by a certain angle, and the scanning cylinder is centered on the target , with a radius of 1m, and the imaging results are shown in Figure 3.

Embodiment 3: This imaging method (method of embodiment 1) is used for the effect verification experiment of active holographic imaging

Test conditions: working frequency 30GHz, antenna element spacing λ/4, array size 66*66, one target is located in the normal direction of the array, the other target deviates from the normal direction by 30°, and the other two targets deviate from the normal direction by a certain angle , the scanning cylinder is centered on the target and has a radius of 1m. The imaging results are shown in Figure 4.

The various embodiments of the present invention are described in a progressive manner, and each embodiment focuses on the difference from other embodiments, and the same and similar parts of the various embodiments can be referred to each other.

The above descriptions are only examples of the present invention, and are not intended to limit the present invention. Various modifications and variations of the present invention will occur to those skilled in the art. Any modification, substitution, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the claims of the present invention.

Claims (13)

1. A cylindrical scanning microwave imaging method, characterized in that the method is based on the principle of lens imaging, combined with electromagnetic field theory, according to the target signal received by the antenna array, weighted by the amplitude and phase of the unit signal, and adopts an efficient parallel algorithm to obtain the target corresponding The image field distribution of , the specific algorithm is as follows:

   

   Among them: j is the imaginary number unit, e is Euler's constant,

   

   is the image field distribution,

   

   is the target signal received by the array unit, A _mn is the amplitude weighting coefficient of the array unit,

   

   is the weighted value for the cylindrical scan amplitude,

   

   is the focus phase weighting coefficient,

   

   is the cylindrical scanning phase compensation coefficient,

   

   is the scanning phase weighting coefficient, M is the number of array units in the x direction, N is the number of array units in the y direction, (x _m , y _n ) is the coordinate of the array unit, (δ, σ) is the coordinate of the image point, V is Image distance, that is, the distance from the imaging plane to the array plane, η is the object selectivity parameter, select different values according to the characteristics of the imaging system, m and n are the serial numbers of the array unit in the x direction and the y direction, respectively,

   

   is the wave number, λ is the wavelength, and the symbol ∑ represents the summation operation.
2. The method according to claim 1, wherein the method is applicable to different imaging systems by selecting different parameter n values, specifically:

   When η=1 is selected, it is suitable for passive imaging system and semi-active imaging system;

   When η=2, it is suitable for active holographic imaging system.
3. The method according to claim 1, characterized in that said method comprises the steps of:

   Step 1: performing amplitude weighting on the array unit signal to reduce the side lobe level;

   Step 2: Perform focus phase weighting on the array unit signals to achieve imaging focus;

   Step 3: Perform cylindrical scanning amplitude compensation and phase compensation on the array unit signal to improve imaging performance;

   Step 4: Perform beam scanning phase weighting on the array unit signals to adjust the central viewing angle direction of the imaging system;

   Step 5: Perform fast imaging processing on array unit signals by using efficient parallel algorithms;

   Step 6: Calculate the coordinates of the image field, and perform coordinate inversion on the image field to obtain the position of the real target.
4. The method according to claim 3, wherein the amplitude weighting method in step 1 includes uniform distribution, cosine weighting, Hamming window, Taylor distribution, Chebyshev distribution and mixed weighting methods.
5. The method according to claim 3, wherein in step 2, performing focus phase weighting on the array element signals to achieve imaging focus, wherein:

   The focus phase calculation formula for auto focus phase weighting is:

   

   Among them, R is the target slant distance, that is, the distance from the target to the center of the array;

   The focus phase calculation formula for zoom or fixed focus phase weighting is:

   

   Among them, F is the focal length, V is the image distance, that is, the distance from the imaging plane to the plane where the receiving array is located, and F<U, F<V.
6. The method according to claim 3, characterized in that, in step 3, performing cylindrical scanning amplitude compensation and phase compensation on the array unit signal to improve imaging performance, wherein:

   The calculation formula of cylindrical scan amplitude compensation is:

   

   in,

   

   Indicates the angle at which the array unit deviates from the center of the array in the polar coordinate system, requiring

   

   When the range of the intercepted synthetic array is small, that is, the equivalent array aperture is small, directly select

   

   to simplify the calculation process.
7. The method according to claim 3, characterized in that, in step 3, performing cylindrical scanning amplitude compensation and phase compensation on the array unit signal to improve imaging performance, wherein:

   The calculation formula of cylindrical scanning phase compensation is:

   

   Among them, ρ is the radius of the scanning cylinder,

   

   Indicates the angle at which the array unit deviates from the array center in the polar coordinate system.
8. The method according to claim 3, wherein the scanning phase weighting in step 4 adjusts the viewing angle direction of the center of the imaging system, and the phase calculation formula of the scanning phase weighting is:

   

   in:

   

   Respectively, the phase difference between adjacent elements of the array in the x and y directions, and their calculation formulas are:

   

   

   in:

   

   is the scanning step angle of cylindrical scanning, is a circle, Δ _y is the array unit spacing in the y direction, θ _ζ and θ _ξ are the scanning angle coordinates in the x and y directions when the central viewing angle direction points to the source coordinates (ζ, ξ), Their calculation formulas are:

   

   

   Among them: U is the object distance, that is, the distance from the plane where the target is located to the array plane.
9. The method according to claim 3, characterized in that in step five, the high-efficiency parallel algorithm is used to perform fast imaging processing on the array unit signal; the high-efficiency parallel algorithm includes two-dimensional or three-dimensional FFT, IFFT, non-uniform FFT, Sparse FFT, its calculation formula is:

   

   where: symbol

   

   represents an efficient parallel algorithm function,

   

   is the target signal received by the array unit, A is the amplitude weighting coefficient of the array unit, A _C is the weighting value of the cylindrical scanning amplitude, φ _F is the focusing phase weighting coefficient, φ _C is the cylindrical scanning phase compensation coefficient, and φ _S is the scanning phase weighting coefficient ;

   The value ranges of ω _δ and ω _σ corresponding to the above image field calculation results are: ω _δ ∈ [0,2π], ω _σ ∈ [0,2π], and after performing fftshift operation, the value ranges of ω _δ and ω _σ are transformed into : ω _δ ∈ [-π, π], ω _σ ∈ [-π, π], the image at this time conforms to the image of the actual distribution:

   
10. The method according to claim 3, wherein step six includes: performing coordinate calculation on the image field obtained by the efficient parallel algorithm, and performing coordinate inversion on the image field to obtain the position of the real target; wherein:

    For the efficient parallel algorithm of the IFFT class, the calculation formula of the image field scanning angle coordinates is:

    

    

    For the efficient parallel algorithm of the FFT class, the calculation formula of the image field scanning angle coordinates is:

    

    

    The formula for calculating the Cartesian coordinates of the image is:

    δ = V tanθ _δ ,

    σ = V tanθ _σ ;

    The coordinate inversion calculation formula of the real target is:

    

    
11. The method according to claim 3, characterized in that, the scan step of setting the transceiver antenna satisfies:

    

    to avoid image aliasing.
12. The method according to any one of claims 1-11, characterized in that the method is also applicable to imaging systems with fixed antennas and rotating targets, including ISAR imaging systems and turntable imaging systems.
13. The application of the method described in any one of claims 1-11 in the fields of optical imaging, microwave imaging, radar detection, sonar, ultrasonic imaging, sound, light, and electrical target detection, imaging recognition, and wireless communication.

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