An airborne vortex radar system target scattering echo simulation method

Abstract

The application discloses a target scattering echo simulation method of an airborne vortex radar system. The implementation steps are as follows: 1. obtaining an angle information sequence of a target relative to the vortex radar system; 2. simulating a target vortex scattering coefficient time domain sequence based on an angle spectrum theory; 3. interpolating the target vortex scattering coefficient time domain sequence; and 4. simulating a vortex radar system target scattering echo time sequence. Firstly, the angle information sequence is calculated by using the motion track and the target position of the airborne vortex radar system planned in advance, and then the physical optical method is used to simulate the target vortex scattering coefficient time domain sequence based on the angle spectrum theory. On this basis, data interpolation and time domain expansion sequence construction are completed, so that the target far-field scattering receiving echo is obtained by combining the inverse Fourier transform and convolution processing. The method provides an efficient simulation approach for target echo simulation of a new system vortex radar.

Description

Technical Field

[0001] This invention belongs to the field of new radar technology, and further relates to radar system echo simulation methods, which can provide an efficient echo simulation means for the development of multi-mode airborne vortex radar systems. Background Technology

[0002] Vortex electromagnetic waves, carrying orbital angular momentum information, possess a higher degree of freedom in information modulation compared to traditional electromagnetic waves, making them highly promising for applications in radar target detection and imaging. As a cutting-edge technology, numerous researchers have explored the OAM (Optical Aspect-Oriented Motion) characteristics of vortex electromagnetic wave radar: in radar imaging, it can achieve super-resolution imaging and high-precision imaging of high-speed targets; in wireless communication, it can significantly increase communication capacity and frequency efficiency; and in target detection, it can sense richer rotating Doppler information about targets. A deeper understanding of the characteristics of this new type of vortex electromagnetic wave radar can promote the development and application of imaging, sensing, and communication technologies.

[0003] Traditional radars rely on the plane wave approximation for target detection, receiving echoes that are scatterings of the plane wave by the target. In contrast, vortex electromagnetic waves possess a helical phase wavefront, and the continuous variation of this wavefront allows for azimuth resolution of radar targets. Compared to traditional radar systems, the development of vortex radar systems focuses on vortex wave antenna transmission and multi-mode reception and demodulation. Besides the design of the system's specifications, evaluating the performance of the target vortex system is crucial for assessing its engineering practicality. While field experiments are cumbersome, costly, and uncontrollable, traditional radar system simulation techniques offer a fast and low-cost way to verify system performance. However, with the increasing demands for electromagnetic simulation systems and the development of digital twin technology in recent years, simulations based solely on statistical models cannot accurately reflect the scattering characteristics of targets under dynamic conditions, failing to meet the technical feedback requirements for developing new vortex radar systems.

[0004] Currently, designing vortex electromagnetic waves that can be transmitted over long distances, maintain high purity, and have a small divergence angle will break through the bottleneck problem restricting the long-term development and application of vortex radar. By combining the design scheme of vortex radar system indicators, the simulation time-domain extended sequence dataset of target scattering coefficients is called in real time and convolved with the radar's transmitted intermediate frequency baseband signal to generate vortex radar target echo signals with target scattering characteristics. This enables rapid evaluation of the vortex radar system indicators and functions, comprehensive verification of the vortex radar's target detection performance, ensuring the system indicator design, and targeted planning of field airborne test schemes to reduce the interference of uncertain factors on field test evaluation.

[0005] In summary, it is necessary to study methods for simulating the target scattering echo of vortex radar to further enhance the engineering application potential of vortex radar systems. Summary of the Invention

[0006] The technical problem solved by this invention is to fill the gap in the echo simulation of new-type vortex radar and to propose a target scattering echo simulation method for airborne vortex radar systems, thereby solving the problems of echo simulation and system performance verification of new-type vortex radar.

[0007] The technical solution of this invention is: a method for simulating target scattering echoes in an airborne vortex radar system, comprising:

[0008] Based on the flight path of the airborne vortex radar system planned in advance, and according to the flight speed of the airborne vortex radar system, the angle information sequence of the target relative to the vortex radar system is calculated.

[0009] Based on the frequency, bandwidth and angle information sequence of the airborne vortex radar system, a time-domain sequence of the target vortex scattering coefficients based on the angle spectrum theory is obtained through simulation.

[0010] The time-domain sequence of the target vortex scattering coefficient is interpolated and extended to obtain the extended time-domain sequence of the target vortex scattering coefficient.

[0011] Based on the time-domain extended sequence of the target vortex scattering coefficient, the target echo signal of the airborne vortex radar system with target scattering characteristics was simulated.

[0012] Preferably, the sequence of angle information of the target relative to the airborne vortex radar system includes:

[0013] Based on the pre-planned flight path of the airborne vortex radar system, and according to the system's flight speed, the geographical coordinates (l0, l) of the vortex radar system at each moment are determined. a According to the geographical coordinates (l0, l) of the airborne vortex radar system, h), a h) Determine the geocentric coordinates (x0, y0, z0) of the airborne vortex radar system;

[0014] Based on the geographic coordinates of the stationary ground target to be measured (l) 0m ,l am ,h m Determine the geocentric coordinates (x1, y1, z1) of the target, and combine them with the latitude and longitude of the target to determine the north-east coordinates (x2, y2, z2) of the target;

[0015] The target radar antenna array coordinates (x3, y3, z3) are determined based on the target's north-east coordinates (x2, y2, z2);

[0016] Determine the azimuth angle of the target relative to the radar in polar coordinates based on the target radar antenna array coordinates (x3, y3, z3). And the pitch angle θ, thus obtaining the angle information sequence.

[0017] Preferably, the simulation-obtained time-domain sequence of target vortex scattering coefficients based on angular spectrum theory includes:

[0018] Assuming the sampling frequency interval of the simulation data is Δf, since f i,1 =f0-B w / 2 is the starting frequency, f i,N =f0+B w / 2 is the termination frequency, then the number of simulated frequency groups N = B w / Δf+1;B w f0 is the bandwidth of the vortex radar, and f0 is the operating center frequency of the vortex radar.

[0019] Using the angle information sequence given in step 1 Wherein, T is the distance L between the vortex radar system and the system. range Related to the velocity V, T = L range / V;

[0020] For the i-th set of angle information, solve for the frequency f. i,p | p＝1,2,3,...N Target scattering coefficients under certain conditions, obtaining T*N time-domain sequences H of scattering coefficients. temp (f i,p ).

[0021] Preferably, the sampling frequency interval of the simulation data is Δf≥0.01GHz.

[0022] Preferably, the interpolation augmentation process is performed according to the sampling rate N. w ≥nB w The number of sampling points is used to expand the time-domain sequence of the target vortex scattering coefficient, n≥2.

[0023] Preferably, the time-domain sequence of the interpolated and expanded scattering coefficients is defined as H0(f i,p The inverse fast Fourier transform is performed on the extended scattering coefficient time-domain sequence to obtain the target vortex scattering coefficient time-domain model data sequence, denoted as h0(t). i,p That is, for each set of angle information The time t of the expanded target vortex scattering coefficient time series is located at time t i,p =(p-(N) w -1) / 2-1)·Δt, the expanded time-domain interval Δt=2 / (N w -1); then for each group The time-domain extended sequence of the target vortex scattering coefficient is as follows:

[0024] h(t i,p )=h0(t i,p)·exp(j2πf0t i,p )

[0025] Preferably, the step of simulating the vortex radar target echo signal with target scattering characteristics based on the time-domain extended sequence of the target vortex scattering coefficient includes:

[0026] The delay of the i-th set of angle sequence sampling is determined based on the distance between the radar and the target;

[0027] The time-domain extended sequence of the target vortex scattering coefficient is used to obtain the vortex radar target echo signal with target scattering characteristics.

[0028] Preferably, based on the obtained vortex radar target echo signal with target scattering characteristics, the pulse compression result after matched filtering of the echo signal is obtained through pulse compression processing, and the simulation resolution is used to verify the performance of the vortex radar system.

[0029] The advantages of this invention compared to the prior art are as follows:

[0030] By combining the trajectory and target position information sequence of an airborne vortex radar system, a target CAD mesh model is established using mature commercial software such as FEKO. The target vortex scattering coefficient is simulated using mature physical optics methods to obtain the time-domain sequence data of the target vortex scattering coefficient. Based on this, data interpolation and time-domain extension sequences are established. Combined with inverse Fourier transform and convolution processing, a target far-field scattering reception echo that is closer to the real scene is obtained. This can solve the design and verification of the performance indicators of a new type of vortex radar system, realize the engineering application development needs of vortex radar systems, and has high practical value. Attached Figure Description

[0031] Figure 1 A block diagram of a method for simulating target scattering echoes in a vortex radar system;

[0032] Figure 2 A schematic diagram of the target flight path detected by a vortex radar and a sequence curve of elevation angles;

[0033] Figure 3 Spatial distribution of amplitude and phase of radiation field of Mode 1 vortex antenna;

[0034] Figure 4 Data on the scattering coefficient of a flat target illuminated by a vortex radar;

[0035] Figure 5 Simulated signal of echo scattered during the flight of vortex radar;

[0036] Figure 6 Target echo pulse compression results of vortex radar system. Detailed Implementation

[0037] The present invention will now be described in further detail.

[0038] The application scenarios of this invention are as follows:

[0039] This invention addresses the problem of target echo simulation for new-type vortex radar systems by proposing a method for simulating target scattering echoes in airborne vortex radar systems. Compared with traditional radar echo simulation methods, this method combines the flight path and target position of the airborne vortex radar system to calculate the detection angle information sequence, utilizes mature commercial software such as FEKO to establish a target CAD mesh model, and employs mature physical optics methods to simulate the target vortex scattering coefficient, obtaining the time-domain sequence data of the target vortex scattering coefficient. Based on this, data interpolation and time-domain extension sequences are established, and combined with inverse Fourier transform and convolution processing, to obtain a target far-field scattering received echo that more closely approximates the real-world scenario. This method can solve the design and verification of performance indicators for new-type vortex radar systems, meet the high reliability development requirements of vortex radar, and has high practical value.

[0040] The implementation steps are as follows:

[0041] Step 1: Obtain the target's angle information sequence relative to the vortex radar system.

[0042] First, the azimuth angle of the target relative to the radar is calculated based on the motion trajectory of the vortex radar system. The relationship between the elevation angle θ and the target coordinate system is mainly based on the coordinate system transformation between the target and the vortex radar system. The real-time geographic coordinates of the radar system are defined as (l0, l... a The geographic coordinates of the stationary target on the ground are (l, h), 0m ,l am ,h m The geographic coordinates were obtained on-site by GPS equipment; the radar geocentric coordinates are (x0, y0, z0), the target geocentric coordinates are (x1, y1, z1), the target's north-sky-east coordinates are (x2, y2, z2), and the target's radar antenna array coordinates are (x3, y3, z3). The expressions for each coordinate are as follows:

[0043] The radar's geocentric coordinates are:

[0044]

[0045]

[0046] In the above formula, l0, l a h and n are the longitude, latitude, and altitude of the radar system, respectively; n is the radius of curvature of the Earth's circumference, e is the first eccentricity, and a is the semi-major axis of the Earth, where a = 6378136.49 m and e = 0.0818.

[0047] The target's geocentric coordinates are:

[0048]

[0049]

[0050] In the above formula, l 0m l am and h m These represent the longitude, latitude, and altitude of the target to be measured;

[0051] The target's north-east coordinates are:

[0052]

[0053] The target radar antenna array coordinates are

[0054]

[0055] In the above formula, α t β is the angle by which the radar antenna array rotates around due east. t This represents the angle of rotation of the radar antenna around the geographic North Pole.

[0056] Therefore, the azimuth and elevation angles of the target relative to the radar in polar coordinates are as follows:

[0057]

[0058] Step 2: Simulate the time-domain sequence of the target vortex scattering coefficients based on angular spectrum theory.

[0059] Assume the vortex radar's operating center frequency is f0 and its bandwidth is B. w The number of equivalent angular spectra of vortex waves based on Bessel beams is set to N. oam That is, the equivalent plane wave angular spectral spacing is dβ=2π / N oam If the half-cone angle of the Bessel beam is α0, then the beam vector of the vortex electromagnetic wave illuminating the target is... Each component can be expressed by the following formula:

[0060]

[0061] In the above formula, the angular spectrum variable β j =jdβ, j = 1, 2, ... N oam λ = c / f0 is the wavelength of the vortex wave radar, and c is the speed of light, typically taken as 3 × 10⁻⁶. 8 m / s.

[0062] Using the physical optics method from published literature, it is possible to simulate a given frequency f0, incident angle θ, and azimuth angle. The target scattering coefficient under the condition, i.e.

[0063]

[0064] In the above formula, M s The number of face elements in the target model mesh, S represents the face element illuminated by the vortex electromagnetic wave, and ds represents the area of ​​a single face element. It can be imported from the commercial software FEKO. R represents the unit vector representing the target's position relative to the vortex radar; ⊥ ,R / / Let R be the reflection coefficients of vertically polarized waves and parallelly polarized waves on the target surface, respectively. For a conductor target R... ⊥ =-1,R / / =1; and The polarization directions of the reflected electric field are parallel and perpendicular to the incident surface; The normal vector of the surface element; The incident field for each angular spectral wave beam is defined by physical optics, with the superscript i indicating the incident wave; k = 2π / λ indicating the spatial wave number of the vortex electromagnetic wave; and l representing the vortex mode value emitted by the vortex radar system.

[0065] In practice, vortex radars have different incident angles θ and azimuth angles. Under certain conditions, the target scattering coefficient is in a swept-frequency data format and is defined as H. temp (f i,p ), where i = 1, 2, 3, ..., T, T is the angle information sequence number; p = 1, 2, ..., N, N is the number of simulation frequency groups.

[0066] The initial simulation is performed at a coarse sampling frequency interval Δf, since f i,1 =f0-B w / 2 is the starting frequency, f i,N =f0+B w / 2 is the termination frequency, then the number of simulated frequency groups N = B w / Δf+1. The input angle parameter information sequence given in step 1 is as follows: Wherein, T is the distance L between the vortex radar and the radar. range Related to the velocity V, T = L range / V; For the i-th set of angle information, solve for the frequency f. i,p | p＝1,2,3,...N Target scattering coefficients under certain conditions, obtaining T*N time-domain sequences H of scattering coefficients. temp (f i,p ).

[0067] Step 3 involves interpolating the time-domain sequence of the target vortex scattering coefficients.

[0068] To ensure distortion-free sampling in the radar system, based on Shannon's sampling theorem, an interpolation algorithm is used according to the sampling rate N. w =2B wThe number of sampling points is increased in step 2 to expand the time-domain data of the scattering coefficients. At this time, the time-domain sequence of the interpolated and expanded scattering coefficients is defined as H0(f i,p The inverse fast Fourier transform is performed on the extended scattering coefficient time-domain sequence to obtain the target vortex scattering coefficient time-domain model data sequence, denoted as h0(t). i,p That is, for each group t i,p =(p-(N) w -1) / 2-1)·Δt,Δt=2 / (N w -1). Then for each group The time-domain extended sequence of the target vortex scattering coefficient is as follows:

[0069] h(t i,p )=h0(t i,p )·exp(j2πf0t i,p (10)

[0070] Step 4: Simulate the target vortex radar scattering echo time series.

[0071] Define the form of the excitation signal transmitted by the vortex radar as s r (t), considering the sampling point delay of the vortex radar and the signal after Doppler processing, convolution calculation with the scattering characteristics time series can yield the vortex radar target echo signal s0(t) with target scattering characteristics, i.e.

[0072]

[0073]

[0074] In the above formula, τ i R is the sampling delay of the i-th angle sequence. i This represents the distance between the target's geocentric coordinates (x1, y1, z1) and the vortex radar system's geocentric coordinates (x0, y0, z0).

[0075] Step 5: Echo signal pulse compression processing to obtain system resolution performance.

[0076]

[0077] The pulse compression result of the echo signal after matched filtering is obtained by pulse compression processing. The simulation resolution is obtained based on the 3dB bandwidth result to verify the performance of the vortex radar system.

[0078] The effects of the present invention will be further illustrated below using simulation data.

[0079] First, quantitatively analyze the far-field target scattering characteristics of a given mode vortex radar. For example... Figure 2As shown in (a), the target location is a simple flat plate. The airborne vortex radar system's flight path is level flight, with a flight altitude of 1000m and a flight speed of 20m / s. The flight distance during this period is 2000m. The target is located in the middle of the flight path. Therefore, the range of the angle information sequence is pitch angle θ = 45 to 90 degrees, and azimuth angle... For 0 and 180 degrees, such as Figure 2 As shown in (b), the target vortex scattering is always backscattering. The vortex radar has a center frequency of 10 GHz, a bandwidth of 600 MHz, and emits vortex electromagnetic waves in mode 1; the incident field of the vortex radar system is... Figure 3 As shown, the far-field RCS of a flat-panel target is simulated using the physical optics method. Coarse sampling is performed at frequency intervals of 0.01MHz for each group. Simulation of target vortex scattering characteristics data yields the following vortex radar illumination pattern for scattering characteristics of a flat-panel target: Figure 4 As shown, by performing convolution calculations on the interpolated time series data, the simulated target echo signal can be obtained, such as... Figure 5 As shown. The range profile is obtained after pulse compression processing of the echo signal, as shown. Figure 6 As shown, the system resolution can be calculated to be 0.252m based on the simulation settings, which is consistent with the system bandwidth design value of 600MHz.

[0080] Simulation analysis conclusions: For vortex radar echo simulation, the method of this invention can obtain target far-field scattering received echoes that are closer to the real scene, and verify the performance of the simulation system.

[0081] The parts of this invention not described in detail are common knowledge to those skilled in the art.

Claims

1. A method for simulating target scattering echoes in an airborne vortex radar system, characterized in that... include: Based on the flight path of the airborne vortex radar system planned in advance, and according to the flight speed of the airborne vortex radar system, the angle information sequence of the target relative to the vortex radar system is calculated. Based on the frequency, bandwidth and angle information sequence of the airborne vortex radar system, a time-domain sequence of the target vortex scattering coefficients based on angular spectrum theory is obtained through simulation. The time-domain sequence of the target vortex scattering coefficient is interpolated and extended to obtain the extended time-domain sequence of the target vortex scattering coefficient. Based on the time-domain extended sequence of the target vortex scattering coefficient, the target echo signal of the airborne vortex radar system with target scattering characteristics was simulated. The calculated sequence of angle information of the target relative to the vortex radar system includes: Based on the pre-planned flight path of the airborne vortex radar system, and according to the system's flight speed, the geographical coordinates of the vortex radar system at each moment are determined. Based on the geographical coordinates of the airborne vortex radar system Determine the geocentric coordinates of the airborne vortex radar system ; Based on the geographic coordinates of the stationary ground target to be measured Determine the geocentric coordinates of the target Based on the target's latitude and longitude, determine the target's north-east coordinates. ; Based on the target's north-east coordinates Determine the target radar antenna array coordinates ; Based on the target radar antenna array coordinates Determine the target's azimuth relative to the radar in polar coordinates. and pitch angle This leads to the angle information sequence; The simulation yields the following time-domain sequence of the target vortex scattering coefficients based on angular spectrum theory: Assume the sampling frequency interval of the simulation data is ,because The starting frequency, To determine the termination frequency, the number of simulated frequency groups is... ; This refers to the bandwidth of the vortex radar. This is the operating center frequency of the vortex radar. Using the given angle information sequence ,in, Distance from vortex radar system and speed of movement Related, ; Regarding the first Set angle information to solve for frequency Target scattering coefficient under certain conditions, obtain Group scattering coefficient time-domain sequence .

2. The method according to claim 1, characterized in that: The simulation data sampling frequency interval is: .

3. The method according to claim 1, characterized in that: The interpolation augmentation process described above is based on the sampling rate. The number of sampling points is used to expand the time-domain sequence of the target vortex scattering coefficients. .

4. The method according to claim 3, characterized in that: The time-domain sequence of interpolated and expanded scattering coefficients is defined as The inverse fast Fourier transform is performed on the extended scattering coefficient time-domain sequence to obtain the target vortex scattering coefficient time-domain model data sequence, denoted as... That is, for each set of angle information The time sequence of the expanded target vortex scattering coefficients at each time point The extended time-domain interval Then for each group The time-domain extended sequence of the target vortex scattering coefficient is as follows: 。 5. The method according to claim 1, characterized in that: The simulation of the vortex radar target echo signal with target scattering characteristics based on the time-domain extended sequence of the target vortex scattering coefficient includes: The distance between the radar and the target is determined. Delay in sampling the group of angle sequences; The time-domain extended sequence of the target vortex scattering coefficient is used to obtain the vortex radar target echo signal with target scattering characteristics.

6. The method according to claim 1, characterized in that: Based on the target echo signal of the vortex radar with target scattering characteristics, the pulse compression result after matched filtering of the echo signal is obtained through pulse compression processing, and the simulation resolution is obtained to verify the performance of the vortex radar system.

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