Vortex electromagnetic wave radar foresight imaging method and system based on concentric ring array design, storage medium and electronic equipment

Abstract

The invention discloses a vortex electromagnetic wave radar foresight imaging method and system based on concentric circular ring array design, a storage medium and electronic equipment, and the method specifically comprises the following steps: building a new system radar imaging model according to a radar working mode; designing a concentric ring array and a vortex mode emission function; deducing an echo model; distance direction high-resolution information of the target is acquired; distance correction, phase decoupling and Bessel amplitude compensation are carried out on the azimuth of the echo, coherent superposition is carried out on the compensated echo, and a dual relation between a mode and an azimuth angle is reconstructed; and finally, realizing vortex electromagnetic wave radar foresight two-dimensional imaging by carrying out fast Fourier transform on the azimuth, and by carrying out foresight imaging through the method, the observation time of the region of interest can be prolonged, the region of interest is enabled to be always in a main lobe range, the echo intensity is enhanced, the echo information is increased, and the azimuth resolution can be effectively improved.

Description

Technical Field

[0001] The present application relates to the field of signal processing technology, and in particular to a forward-looking imaging method, system, digitally readable storage medium and electronic device for a vortex electromagnetic wave radar based on a concentric ring array design. Background Art

[0002] Microwave imaging is not restricted by climatic conditions and works all day and all weather. It is widely used in geological exploration, damage assessment, forest remote sensing, reconnaissance and surveillance, etc. Radar imaging technology represented by synthetic aperture radar uses large transmission bandwidth and synthetic aperture processing technology to achieve high resolution in distance and azimuth. However, when the radar is required to work in forward-looking mode, the Doppler bandwidth drops sharply, and the Doppler information cannot be used for azimuth processing to obtain high-resolution azimuth, making it difficult to achieve forward-looking target imaging, and there is an inherent blind spot in the field of vision.

[0003] In recent years, orbital angular momentum has provided a new degree of freedom for information transmission and has attracted great attention in the field of radar imaging. Electromagnetic waves carrying orbital angular momentum are called vortex electromagnetic waves, which have spiral phase characteristics. Their wavefronts propagate in a spiral along the beam axis in space. The phase difference of the echo is the key to radar imaging, so this characteristic provides a new possibility for its application in the field of forward-looking imaging.

[0004] Most of the previous vortex electromagnetic wave radars use uniform circular arrays to generate vortex electromagnetic waves. As the emission mode changes, the main lobe of the electromagnetic wave will also change accordingly, and it cannot be guaranteed that the main lobe always illuminates the area of ​​interest. This paper uses a concentric ring array to independently emit multi-mode vortex electromagnetic waves in time-sharing, so that electromagnetic waves of different modes always illuminate the same area, realizing a beam-forming mode similar to that in synthetic aperture radar; based on the geometric configuration of the forward-looking radar imaging scene and the concentric ring array, an echo signal model is constructed, and improvements are made on the original range Doppler algorithm, with phase and amplitude compensation added, and the coherent superposition method is used to make the mode and azimuth angle satisfy the dual relationship in Fourier transform again, so as to obtain the target azimuth information, which makes up for the inherent blind spot of radar imaging. Summary of the invention

[0005] The purpose of the present application is to provide a vortex electromagnetic wave radar forward imaging method, system, storage medium and electronic device based on a concentric ring array design to solve or alleviate the problems existing in the above-mentioned prior art.

[0006] In order to achieve the above objectives, this application provides the following technical solutions:

[0007] The present application provides a forward-looking imaging method of a vortex electromagnetic wave radar based on a concentric ring array design. The method includes: step S101, establishing a new radar imaging model according to the radar working mode; step S102, designing a concentric ring array and a vortex mode emission function; step S103, deriving an echo model according to the relative motion between the radar and the target; step S104, emitting a large-bandwidth linear frequency modulation signal in the distance direction to obtain high-resolution information of the target distance direction; step S105, performing distance correction on the echo obtained after pulse compression; step S106, performing azimuth modulation phase decoupling and Bessel amplitude compensation on the echo after distance correction, and coherently superimposing the compensated echo to reconstruct the dual relationship between the mode and the azimuth angle; step S107, performing a fast Fourier transform on the azimuth direction to reconstruct a two-dimensional image.

[0008] Preferably, in step S101, the geometric configuration of radar imaging is established according to the forward-looking working mode of the radar, and the pitch angle θ between the radar and the target is defined as the angle between the target and the flight direction of the radar; the azimuth angle is defined as It is the angle between the projection of the distance between the radar and the target on the circular array plane and the altitude axis.

[0009] Preferably, in step S102, a vortex emission pattern that changes linearly with slow time is designed:

[0010]

[0011] Where η represents the slow time, i.e., the radar flight time; K l Indicates the mode switching rate; l ini is the mode of radar emission at the initial moment.

[0012] And the radius of the concentric ring array is calculated and designed according to the azimuth relationship between the radar and the target:

[0013]

[0014] Where x(η) represents a set of values ​​of the main lobe pointing angle of the Bessel function in the current transmission mode, a(η) represents the radius of the designed concentric rings, k represents the wave number of the signal, a represents the ring radius used at the initial moment, and J l (x) denotes the Bessel function of the first kind of order l.

[0015] Preferably, in step S103, an echo signal model is derived according to the relative motion between the radar and the target:

[0016]

[0017] Among them, θ(η) is the pitch angle at each moment, r(η) is the instantaneous slant range between the radar and the target, represents the azimuth of the target, f0 represents the carrier frequency of the signal, K r is the frequency modulation slope of the linear frequency modulation signal, and c represents the speed of light. Among them, θ(η) can be expressed as:

[0018]

[0019] Where r0 represents the initial distance between the radar and the target, θ0 represents the initial pitch angle between the radar and the target, and v represents the movement speed of the radar carrier.

[0020] Preferably, in step S104, a linear frequency modulation signal with a large bandwidth is transmitted in the range direction, and high-resolution information of the target range direction is obtained by pulse compression. The signal after down-conversion and pulse compression can be expressed as:

[0021]

[0022] where w r [·] represents the distance envelope, B w represents the range pulse bandwidth, f c represents the carrier frequency, k represents the wave number, and a represents the radius of the ring.

[0023] Using the relative motion between the carrier and the target, we can deduce:

[0024]

[0025] Taylor expansion of the instantaneous slope distance can be obtained.

[0026]

[0027] Preferably, in step S105, the echo obtained in step S104 after the range pulse compression is transformed into the range Doppler domain, and the distance is corrected using the range Doppler algorithm. The obtained signal can be expressed as:

[0028]

[0029] Preferably, in step S106, a phase compensation factor and a Bessel amplitude compensation factor are designed to compensate the echo, wherein the phase compensation factor h liner (η) can be expressed as:

[0030]

[0031] The Bessel amplitude compensation factor can be expressed as follows according to the designed vortex emission mode and the target revisit angle:

[0032]

[0033] The compensated echo can be expressed as:

[0034]

[0035] Then the echoes are coherently superimposed in the slow time domain to transform them into the modal domain:

[0036]

[0037] After the above compensation and coherent superposition, the mode and azimuth in the echo signal satisfy the dual relationship again.

[0038] Preferably, in step S107, the signal obtained in step S106 is subjected to a fast Fourier transform in the modal domain to obtain the azimuth information of the target and obtain a focused two-dimensional target image.

[0039]

[0040] where w a [·] represents the azimuthal envelope, B l Represents the total number of modes in the modal domain.

[0041] The embodiment of the present application also provides a vortex electromagnetic wave radar forward imaging system based on a concentric ring array design, including: a data acquisition unit, configured to receive the echo signal of the irradiated imaging area; a pulse compression unit, configured to perform pulse compression on the echo in the range direction. Based on this, high-resolution information on the distance of the target is obtained; a distance correction unit, configured to perform distance correction in azimuth; a compensation unit, configured to compensate for the azimuth modulation phase and Bessel amplitude of the echo; a coherent superposition unit, configured to perform azimuth superposition on the compensated echo in a certain manner to reconstruct the dual relationship between the mode and the azimuth angle; an azimuth focusing unit, configured to perform a fast Fourier transform on the modal domain of the superimposed signal, based on which a two-dimensional image is reconstructed.

[0042] Beneficial effects:

[0043] In the forward-looking imaging method of the vortex electromagnetic wave radar based on the concentric ring array design provided by the present application, first, a new radar imaging model is established according to the radar working mode. Then, the concentric ring array and the vortex mode emission function are designed. Based on the radar imaging model, the concentric ring array and the vortex mode emission function, the echo model is derived according to the relative motion between the radar and the target. Based on the linear frequency modulation signal with a large bandwidth, the high-resolution information of the target distance is obtained by pulse compression in the distance direction. The pulse compressed signal is transformed into the range Doppler domain, and the range Doppler algorithm is used for distance correction. Based on the azimuth modulation phase and Bessel amplitude modulation generated during the radar movement, phase and amplitude compensation are performed. For the compensated signal, the coherent superposition in the slow time direction is performed according to the designed vortex mode emission function, and the dual relationship between the vortex mode and the azimuth angle is reconstructed. Based on the dual relationship between the vortex mode and the azimuth angle, the modal domain of the signal after coherent superposition is fast Fourier transformed to reconstruct a two-dimensional image. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] The drawings constituting part of the present application are used to provide a further understanding of the present application. The exemplary embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. Among them:

[0045] Figure 1 It is a schematic diagram of the process of the present invention;

[0046] Figure 2 Single-point target and multi-point target simulation images and azimuth slice images provided for some embodiments of the present invention;

[0047] Figure 3 The point target simulation image and azimuth slice image obtained by traditional method;

[0048] Figure 4 Geometric configuration diagrams provided for some embodiments of the present invention;

[0049] Figure 5 This is a unit configuration diagram of the present invention. DETAILED DESCRIPTION

[0050] The present application will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments. Each example is provided by way of explanation of the present application and does not limit the present application. In fact, it will be clear to those skilled in the art that modifications and variations may be made in the present application without departing from the scope or spirit of the present application. For example, a feature shown or described as a part of an embodiment may be used in another embodiment to produce yet another embodiment. Therefore, it is desired that the present application includes such modifications and variations within the scope of the appended claims and their equivalents.

[0051] Exemplary Methods

[0052] like Figure 1 As shown, the vortex electromagnetic wave radar forward imaging method based on the concentric ring array design includes:

[0053] In step S101, the geometric configuration of radar imaging is established according to the forward-looking working mode of the radar, and the pitch angle θ between the radar and the target is defined as the angle between the target and the flight direction of the radar; the azimuth angle is defined as It is the angle between the projection of the distance between the radar and the target on the circular array plane and the altitude axis.

[0054] In step S102, a vortex emission pattern that varies linearly with slow time is designed:

[0055]

[0056] Where η represents the slow time, i.e., the radar flight time; K l Indicates the mode switching rate; l ini is the mode of radar emission at the initial moment.

[0057] And the radius of the concentric ring array is calculated and designed according to the azimuth relationship between the radar and the target:

[0058]

[0059] Where x(η) represents a set of values ​​of the main lobe pointing angle of the Bessel function in the current transmission mode, and a(η) represents the radius of the designed concentric rings.

[0060] In step S103, the echo signal model is derived according to the relative motion between the radar and the target:

[0061]

[0062] Among them, θ(η) is the pitch angle at each moment, r(η) is the instantaneous slant range between the radar and the target, and θ(η) can be expressed as:

[0063]

[0064] Where r0 represents the initial distance between the radar and the target, θ0 represents the initial pitch angle between the radar and the target, and v represents the movement speed of the radar carrier.

[0065] In step S104, it is assumed that a linear frequency modulation signal with a large bandwidth is transmitted in the range direction, and high-resolution information of the target range direction is obtained by pulse compression. The signal after down-conversion and pulse compression can be expressed as:

[0066]

[0067] where w r [·] represents the distance envelope, B w represents the range pulse bandwidth, f c represents the carrier frequency, k represents the wave number, and a represents the radius of the ring.

[0068] Using the relative motion between the carrier and the target, we can deduce:

[0069]

[0070] Taylor expansion of the instantaneous slope distance can be obtained.

[0071]

[0072] In step S105, the echo obtained in step S104 after the range pulse compression is transformed into the range Doppler domain, and the range is corrected using the range Doppler algorithm. The obtained signal can be expressed as:

[0073]

[0074] In step S106, a phase compensation factor and a Bessel amplitude compensation factor are designed to compensate the echo, wherein the phase compensation factor h liner (η) can be expressed as:

[0075]

[0076] The Bell amplitude compensation factor can be expressed as follows according to the designed vortex launch mode and target revisit angle:

[0077]

[0078] The compensated echo can be expressed as:

[0079]

[0080] Then the echoes are coherently superimposed in the slow time domain to transform them into the modal domain:

[0081]

[0082] After the above compensation and coherent superposition, the mode and azimuth in the echo signal satisfy the dual relationship again.

[0083] In step S107, the signal obtained in step S106 is subjected to a fast Fourier transform in the modal domain to obtain the azimuth information of the target and obtain a focused two-dimensional target image.

[0084]

[0085] where w a [·] represents the azimuthal envelope, B l Represents the total number of modes in the modal domain.

[0086] This method can increase the observation time of the area of ​​interest and keep the area of ​​interest within the main lobe, enhance the amplitude of the echo and increase the information of the echo. This method improves the range Doppler algorithm. The improved algorithm can quickly decouple the azimuth and slow time information and perform echo amplitude compensation. Figure 2 Single point target and Figure 3 It can be seen from the azimuth slice diagram that the azimuth focused image obtained by this method through simulation experiments is at least 2.4 times higher than that of the traditional method.

[0087] Exemplary Systems

[0088] The present application also provides a vortex electromagnetic wave radar forward imaging system based on a concentric ring array design, such as Figure 5 As shown, it includes: a data acquisition unit, configured to receive the echo signal of the irradiated imaging area; a pulse compression unit, configured to perform pulse compression on the range echo. Based on this, high-resolution information of the target in the range is obtained; a distance correction unit, configured to perform distance correction in azimuth; a compensation unit, configured to compensate the azimuth modulation phase and Bessel amplitude of the echo; a coherent superposition unit, configured to perform azimuth superposition on the compensated echo in a certain way to reconstruct the dual relationship between the mode and the azimuth angle; an azimuth focusing unit, configured to perform fast Fourier transform on the modal domain of the superimposed signal, based on which a two-dimensional image is reconstructed.

[0089] The vortex electromagnetic wave radar forward-looking imaging method based on the concentric ring array design provided in the embodiment of the present application can realize target imaging at any forward-looking angle, which will not be described in detail here.

[0090] Exemplary Devices

[0091] The present application provides an electronic device, including a storage medium, an antenna, and a processor; the processor is suitable for executing various programs; the antenna is used to receive and transmit signals; and the memory is used to store multiple programs; it is characterized in that when the memory executes the program on the processor, the vortex electromagnetic wave radar forward-looking imaging method based on the concentric ring array design is implemented.

[0092] Since the vortex electromagnetic wave radar forward-looking imaging based on the concentric ring array design has been introduced in detail in the specific implementation method example, it will not be described in detail here.

[0093] Among them, the antenna includes a single pulse antenna and an array antenna, which is one of the most critical components in the radar system; the memory includes a digital radio frequency memory; the processor includes a central processing unit (CPU), a network processor (NP), etc., and can also be a digital signal processor, a dedicated integrated circuit, a ready-made programmable gate array, a control circuit or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component. The methods, steps and logic block diagrams disclosed in the embodiments of this application can be implemented or executed. The general processor can be a microprocessor or the processor can also be any conventional processor, etc.

[0094] The antenna may be specifically configured to transmit linear frequency modulation signals carrying different modes and receive echoes.

[0095] The processor can be specifically configured as follows: performing pulse compression on the range echo, based on which high-resolution information of the target in the range is obtained; performing distance correction on the azimuth; performing azimuth modulation phase and Bessel amplitude compensation on the distance-corrected signal; performing azimuth coherent superposition on the compensated signal in a certain manner to reconstruct the dual relationship between the mode and the azimuth angle; performing fast Fourier transform on the modal domain of the superimposed signal, based on which a two-dimensional image is reconstructed.

[0096] It should be pointed out that, according to the needs of implementation, the various components / steps 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 components / steps can be combined into new components / steps to achieve the purpose of the embodiments of the present application.

[0097] The above-mentioned method according to the embodiment of the present application can be implemented in hardware, software, or a combination of hardware and software. The hardware part can be implemented using dedicated logic; the software part can be stored in a memory (such as a CD ROM, RAM, hard disk or disk), or can be implemented by downloading the original storage through the network in a remote recording medium or a non-temporary machine storage medium, and there are appropriate instructions pointing to the system and method for execution. 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 special-purpose computer for executing the method shown herein.

[0098] A person skilled in the art will appreciate that the above-mentioned devices and methods can be implemented using computer executable instructions or included in processor control code. Whether these functions are implemented in the form of hardware and software, or a combination of hardware and software, depends on the specific application and constraints involved in the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the embodiments of the present application.

[0099] It should be noted that the various embodiments in this specification are described in a progressive manner, and the same or similar parts between the various 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, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiments.

[0100] The device and system embodiments described above are merely illustrative, wherein the units not shown as separate may or may not be physically separated, and the units not shown as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Those of ordinary skill in the art may understand and implement it without creative work.

[0101] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. For those skilled in the art, the present application may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the protection scope of the present application.

Claims

1. A vortex electromagnetic wave radar forward imaging method based on a concentric ring array design, characterized in that: include: Step S101: Establish a new radar imaging model according to the radar working mode, define the pitch angle θ between the radar and the target as the angle between the target and the radar flight direction; define the azimuth angle It is the angle between the distance between the radar and the target and the height axis of the projection of the circular array plane; Step S102, designing a concentric ring array and a vortex mode launch function; Step S103, deriving an echo model according to the relative motion between the radar and the target; Step S104, transmitting a large bandwidth linear frequency modulation signal in the range direction, and obtaining high-resolution information of the target range direction through pulse compression; Step S105, performing distance correction on the signal obtained by the distance pulse compression in step S104; Step S106, decoupling and Bessel amplitude compensation are performed on the azimuth phase modulation item of the distance-corrected echo obtained in step S105, and coherent superposition is performed in the slow time domain to reconstruct the dual relationship between the mode and the azimuth angle; Step S107: Perform fast Fourier transform in azimuth on the slow-time decoupled signal obtained in step S106 to obtain a forward-looking two-dimensional focused image of the vortex electromagnetic wave radar.

2. The vortex electromagnetic wave radar forward imaging method based on concentric ring array design according to claim 1 is characterized in that: The vortex mode emission function described in step S102 is a vortex emission mode that varies linearly with slow time: Where η represents the slow time, i.e., the radar flight time; K l Indicates the mode switching rate; l ini is the mode of radar emission at the initial moment, represents the floor function; And the radius of the concentric ring array is calculated and designed according to the azimuth relationship between the radar and the target: Where x(η) represents a set of values ​​of the main lobe pointing angle of the Bessel function in the current transmission mode, a(η) represents the radius of the designed concentric rings, k represents the wave number of the signal, a represents the ring radius used at the initial moment, and J l (x) denotes the Bessel function of the first kind of order l.

3. The vortex electromagnetic wave radar forward imaging method based on concentric ring array design according to claim 1 is characterized in that: The echo signal model in step S103 is: Among them, θ(η) is the pitch angle at each moment, r(η) is the instantaneous slant range between the radar and the target, represents the azimuth of the target, f0 represents the carrier frequency of the signal, K r is the frequency modulation slope of the linear frequency modulation signal, c represents the speed of light; where θ(η) can be expressed as: Where r0 represents the initial distance between the radar and the target, θ0 represents the initial pitch angle between the radar and the target, v represents the movement speed of the radar carrier, k represents the wave number, and a represents the radius of the ring.

4. The vortex electromagnetic wave radar forward imaging method based on concentric ring array design according to claim 1 is characterized in that: The step S104 specifically includes the following steps: transmitting a linear frequency modulation signal with a large bandwidth in the range direction, obtaining high-resolution information of the target range direction by pulse compression, and the signal after down-conversion and pulse compression is expressed as: where w r [·] represents the distance envelope, B w represents the range pulse bandwidth, f c represents the carrier frequency, k represents the wave number, and a represents the radius of the ring. Using the relative motion between the carrier and the target, we can deduce: Taylor expansion is performed on the instantaneous slope distance obtained to obtain:

5. The vortex electromagnetic wave radar forward imaging method based on concentric ring array design according to claim 1 is characterized in that: In step S105, the echo obtained in step S104 after the range pulse compression is transformed into the range Doppler domain, and the range is corrected using the range Doppler algorithm. The obtained signal can be expressed as:

6. The vortex electromagnetic wave radar forward imaging method based on concentric ring array design according to claim 1 is characterized in that: In step S106, a phase compensation factor and a Bessel amplitude compensation factor are designed to compensate the echo, wherein the phase compensation factor h liner (η) is expressed as: The Bell amplitude compensation factor is expressed as follows based on the designed vortex launch mode and the target revisit angle: The echo after compensation is expressed as: Then the echoes are coherently superimposed in the slow time domain to transform them into the modal domain: After the above compensation and coherent superposition, the mode and azimuth in the echo signal satisfy the dual relationship again.

7. The vortex electromagnetic wave radar forward imaging method based on concentric ring array design according to claim 1 is characterized in that: In step S107, the signal obtained in step S106 is subjected to a fast Fourier transform in the modal domain to obtain the azimuth information of the target and obtain a focused two-dimensional target image: where w a [·] represents the azimuthal envelope, B l Represents the total number of modes in the modal domain.

8. A vortex electromagnetic wave radar forward imaging system based on a concentric ring array design, characterized in that: include: a data acquisition unit configured to receive an echo signal of the irradiated imaging area; A pulse compression unit configured to perform pulse compression on the range echo; Based on this, high-resolution information of the target's distance is obtained; A distance correction unit configured to perform distance correction in azimuth; a compensation unit configured to compensate for the azimuth modulation phase and Bessel amplitude of the echo; A coherent superposition unit is configured to perform azimuth superposition on the compensated echoes in a certain manner to reconstruct the dual relationship between the mode and the azimuth; The azimuth focusing unit is configured to perform fast Fourier transform on the modal domain of the superimposed signal and reconstruct a two-dimensional image based on the fast Fourier transform.

9. A storage medium storing a plurality of programs, characterized in that: The program application is loaded and executed by a processor to implement the vortex electromagnetic wave radar forward-looking imaging method based on a concentric ring array design as described in any one of claims 1-7.

10. An electronic device, comprising a storage medium and a processor; the processor is adapted to execute various programs; and the memory is adapted to store a plurality of programs; characterized in that: When the memory executes the program on the processor, the vortex electromagnetic wave radar forward-looking imaging method based on concentric ring array design as described in any one of claims 1-7 is implemented.

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