A method for modeling and simulating ground clutter while a vehicle-mounted radar is in motion

Abstract

This invention specifically relates to a method for modeling and simulating ground clutter in a moving vehicle-mounted radar system. The method includes: setting vehicle-mounted radar parameters so that the radar transmits pulse trains at equal periodic intervals during movement; setting vehicle platform motion parameters; sampling ground clutter azimuth and range; calculating the amplitude of the received ground clutter echo signal based on the radar parameters; calculating the Doppler frequency based on the vehicle platform motion parameters; calculating the phase of the ground clutter echo signal based on the Doppler frequency; and calculating the ground clutter echo signal based on the phase and amplitude of the ground clutter echo signal. This method fully considers the influence of various factors such as radar operating frequency, radar height, beam pointing, beam gain, signal bandwidth, and platform motion on the ground clutter echo, and performs simulation modeling of the radar ground clutter echo signal within a single CPI, resulting in simulated data that more closely approximates the real-world scenario.

Description

Technical Field

[0001] This invention relates to the field of radar technology, and in particular to a method for modeling and simulating ground clutter in vehicle-mounted radar while it is in motion, which is applicable to the simulation of complex working environments of vehicle-mounted radar. Background Technology

[0002] Vehicle-mounted reconnaissance radar primarily detects ground targets such as personnel, vehicles, and low-altitude aircraft. Due to the unique nature of its operating environment, it is mainly affected by ground clutter interference during target detection. The clutter components in the echo data exhibit composite characteristics, and their amplitude characteristics and inter-pulse correlations differ from those of conventional single-type clutter. In research and engineering applications, due to the difficulty in controlling and repeatability of field tests, as well as the high demands on manpower, material resources, and financial resources, radar engineers often use simulated data to replace field test data. The quality of a clutter model hinges on its ability to realistically simulate the relevant characteristics of clutter under actual testing conditions. Excellent clutter models often act as clutter signal sources in radar systems, providing clutter data for the research and development and upgrading of radar signal processing and other systems. Besides facilitating the creation of more ideal radar system models by radar simulator designers, it also helps signal engineers gain a deeper understanding of the characteristics of various signal processing methods, providing theoretical support for related design decisions and maximizing the elimination of the adverse effects of clutter interference on the performance of related radar products by combining specific technologies.

[0003] Extensive research and experimentation have been conducted on clutter characteristics, leading to the establishment of various statistical models to further analyze clutter formation mechanisms. Common clutter amplitude distribution models include Rayleigh, Weibull, log-normal, and K-distribution. When radar clutter primarily originates from meteorological interference or low radar resolution, the clutter envelope follows a Rayleigh distribution. The Rayleigh distribution is a limiting distribution, primarily influenced by a single parameter, and theoretically derived from the central limit theorem. Because the Rayleigh distribution has the shortest tail, and both in-phase and quadrature components of the clutter satisfy a Gaussian sequence, it is also called Gaussian clutter. Existing clutter simulation methods mainly include the Zero Memory Nonlinear Transform (ZMNL) method and the Spherically Invariant Random Process (SIRP) method. The ZMNL method transforms an uncorrelated Gaussian sequence into a correlated Gaussian sequence, then identifies a nonlinear transformation that transforms it into a correlated non-Gaussian sequence. Applying the SIRP method to generate clutter data allows for independent control of the probability density function and power spectral density function characteristics, ensuring they are unaffected by each other and facilitating data generation.

[0004] The above clutter simulation methods essentially generate correlated random sequences with specific distributions, without considering the impact of radar parameters such as frequency, signal bandwidth, antenna gain modulation, and platform motion on clutter echoes. Furthermore, the correlation of clutter echoes within a single CPI cannot be achieved, resulting in traditional methods being unable to realistically simulate ground clutter echo signals from radars on vehicle platforms.

[0005] It should be noted that the information disclosed in the background section above is only used to enhance the understanding of the background of the present invention, and therefore may include information that does not constitute prior art known to those skilled in the art. Summary of the Invention

[0006] This invention provides a method for modeling and simulating ground clutter of a vehicle-mounted radar while it is in motion. It takes into account the influence of radar parameters on clutter echoes and can more realistically simulate the ground clutter echo signal of the radar under the vehicle platform.

[0007] Other features and advantages of the invention will become apparent from the following detailed description, or may be learned in part by practice of the invention.

[0008] According to a first aspect of the present invention, a method for modeling and simulating ground clutter during vehicle-mounted radar travel is provided, the method comprising: setting parameters of the vehicle-mounted radar such that the vehicle-mounted radar transmits pulse trains at equal periodic intervals during travel;

[0009] Set the motion parameters of the vehicle platform;

[0010] Ground clutter azimuth and range sampling is performed, and the amplitude of the ground clutter echo signal received by the radar is calculated based on radar parameters. The Doppler frequency is calculated based on the motion parameters of the vehicle platform.

[0011] The phase of the ground clutter echo signal is calculated based on the Doppler frequency, and the ground clutter echo signal is calculated based on the phase and amplitude of the ground clutter echo signal.

[0012] In some exemplary embodiments, the radar parameters include:

[0013] CPI internal coherent pulse number K, pulse repetition period T, pulse width τ, signal instantaneous bandwidth B, radar operating frequency f0, peak power P t and radar antenna gain

[0014] In some exemplary embodiments, the motion parameters of the vehicle platform include a motion velocity vector.

[0015] In some exemplary embodiments, the calculation of the radar received ground clutter echo signal amplitude based on radar parameters specifically includes:

[0016]

[0017] Where λ is the radar signal wavelength, R C,n Where σ is the distance between the ground object and the radar, F is the system loss; C The scattering cross-section of the ground object, θ represents the elevation angle of ground features relative to the radar at different range rings. mThe azimuth angle of the azimuth sampling point.

[0018] In some exemplary embodiments, the calculation of Doppler frequency based on the motion parameters of the vehicle platform specifically includes:

[0019]

[0020] Among them, v d,m,n = <v,a m,n >, v is the velocity vector of the vehicle platform, a m,n This is the motion direction vector of the vehicle platform.

[0021] In some exemplary embodiments, the method further includes:

[0022] To ensure that the Doppler values ​​of the radar received data are not blurred, the azimuth sampling interval should be reasonably selected to ensure that the radar Doppler resolution is not less than twice the average Doppler frequency increment of the center distance around the ground features.

[0023] In some exemplary embodiments, the calculation of the ground clutter echo signal phase based on the Doppler frequency specifically involves:

[0024]

[0025] In some exemplary embodiments, the calculation of the ground clutter echo signal based on the phase and amplitude of the ground clutter echo signal specifically involves:

[0026]

[0027] Where k = 1, 2, ..., K represents the number of pulses, z n (m) represents the random amplitude, which follows a Gaussian distribution N(0,1), and w(t) represents Gaussian white noise.

[0028] According to a second aspect of the present invention, a storage medium is provided having a computer program stored thereon, which, when executed by a processor, implements the vehicle-mounted radar ground clutter modeling and simulation method described in the first aspect above.

[0029] According to a third aspect of the present invention, a computer program product is provided, on which a computer program is stored, wherein when the computer program is executed by a processor, the above-described method for modeling and simulating ground clutter during vehicle-mounted radar travel is implemented.

[0030] The embodiments of this invention provide a simulation method for modeling ground clutter on the move by a vehicle-mounted radar. Based on the actual working scenario of a vehicle-mounted battlefield reconnaissance radar, the simulation model fully considers the influence of various factors such as radar operating frequency, radar elevation, beam pointing, beam gain, signal bandwidth, and platform motion on ground clutter echoes. It simulates and models the radar ground clutter echo signal within a single CPI, resulting in simulation data that more closely approximates the real scenario. During movement, the vehicle-mounted radar transmits pulse trains at equal periodic intervals. These pulses are reflected by ground objects and received by the radar. The radar signal processor then performs MTD filtering on the received echo signals to improve radar detection performance.

[0031] It should be understood that the above general description and the following detailed description are exemplary and explanatory only, and are not intended to limit the invention. Attached Figure Description

[0032] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the invention and, together with the description, serve to explain the principles of the invention. It is obvious that the drawings described below are merely some embodiments of the invention, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort.

[0033] Figure 1 A flowchart illustrating a method for modeling and simulating ground clutter while a vehicle-mounted radar is in motion, as provided in an embodiment of the present invention.

[0034] Figure 2 The method provided in this invention provides simulation data of a single-pulse ground clutter time-domain echo.

[0035] Figure 3 The method provided in this invention simulates the echo data after compression of a single CPI internal clutter pulse.

[0036] Figure 4 The method provided in this invention is used to simulate the echo data after the MTD of clutter in a single CPI. Detailed Implementation

[0037] Exemplary embodiments will now be described more fully with reference to the accompanying drawings. However, these exemplary embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, they are provided so that the invention will be more comprehensive and complete, and will fully convey the concept of the exemplary embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0038] Furthermore, the accompanying drawings are merely illustrative of the invention and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and therefore repeated descriptions of them will be omitted. Some block diagrams shown in the drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software, in one or more hardware modules or integrated circuits, or in different network and / or processor devices and / or microcontroller devices.

[0039] This invention provides a simulation method for modeling ground clutter in a moving vehicle-mounted radar system. Based on the actual working scenario of a vehicle-mounted battlefield reconnaissance radar, this invention performs simulation modeling, fully considering the influence of various factors such as radar operating frequency, radar elevation, beam pointing, beam gain, signal bandwidth, and platform movement on ground clutter echoes. It simulates and models the radar ground clutter echo signal within a single CPI, resulting in simulation data that more closely approximates the real scenario. During movement, the vehicle-mounted radar transmits pulse trains at equal periodic intervals, which are reflected by ground objects and received by the radar. The radar signal processor then performs MTD filtering on the received echo signals to improve radar detection performance. To recreate the real scenario, the simulation model established in this invention: 1) considers the influence of sidelobe clutter on top of the main lobe clutter; 2) the intensity of ground clutter echoes at different distances is affected by antenna gain and radar equations; 3) considering the influence of the moving platform, the Doppler center of the ground clutter is not at zero frequency, and this frequency center is related to the beam pointing and the speed of the vehicle-mounted platform.

[0040] Figure 1 A flowchart of a method for modeling and simulating ground clutter while a vehicle-mounted radar is in motion, provided in an embodiment of the present invention, includes the following steps:

[0041] Step 1: Radar parameter settings: CPI internal coherent pulse number K, pulse repetition period T, pulse width τ, signal instantaneous bandwidth B, radar operating frequency f0, peak power P t and radar antenna gain

[0042] Step 2: Simulation settings for vehicle motion platform parameters: Platform motion velocity vector v, assuming the radar beam direction is... θ0 is the azimuth direction of the beam center in the geodetic coordinate system. If the beam center is in the elevation direction in the geodetic coordinate system, then the direction vector is:

[0043] Based on the above information, the projected velocity of the platform's motion velocity vector in the beam pointing direction is v. d =<v,a0> , where the symbol <·> represents the inner product of two vectors. At this time, the radar beam center receives the ground clutter Doppler center as...

[0044]

[0045] Where λ is the radar signal wavelength.

[0046] Step 3: Assume the set of azimuth sampling points is {θ} m The distance ring set is {R, m = 1, 2, ..., M}. C,n The amplitude of the ground clutter echo signal received by the radar is given by the expression for the input signal n = 1, 2, ..., N.

[0047]

[0048] Among them, R C Let σ be the distance between the ground object and the radar, and F be the system loss. C Let be the ground object's scattering cross-section, and its corresponding Doppler frequency be .

[0049]

[0050] Among them, v d,m,n = <v,a m,n >,

[0051] Step 4: To ensure that the Doppler values ​​of the radar received data are not blurred, the azimuth sampling interval Δθ should be reasonably selected to ensure that the radar Doppler resolution is not less than twice the average Doppler frequency increment of the center distance around the ground objects.

[0052] Step 5: Calculate the ground clutter phase information of the m-th azimuth sample in the nth range loop.

[0053]

[0054] Ignoring the influence of inter-pulse clutter amplitude fluctuations, the received N range loop echo signals are:

[0055]

[0056] Where k = 1, 2, ..., K represents the number of pulses. n (m) represents the random amplitude, which follows a Gaussian distribution N(0,1), and w(t) represents Gaussian white noise.

[0057] The following will describe in more detail each step of the phased array radar design method in this exemplary embodiment, with reference to the accompanying drawings and embodiments.

[0058] Step 1: Within one coherent processing interval, the vehicle-mounted radar transmitter sequentially transmits K coherent pulses of the same period, with a pulse repetition period (PRT) of T, a pulse width of τ, a signal instantaneous bandwidth of B, a radar operating frequency of f0, and a peak power of P. tThe radar antenna gain is Where θ is the azimuth angle. Where is the elevation angle. At this point, the maximum unambiguous radar range is... Radar range resolution c is the speed of light. Assume the radar baseband transmitted waveform is a linear frequency modulated signal:

[0059]

[0060] in, This represents the frequency modulation slope. The baseband sampling frequency is F. s The baseband sampling frequency is required to be F. s Satisfying the Nyquist sampling theorem, i.e., F s ≥2B.

[0061] Step 2, Simulation settings for vehicle motion platform parameters: Platform motion velocity vector v = [v x ,v y ,v z ] T , where v x v y v z These represent the eastward speed, the northward speed, and the celestial speed, respectively. [·] T This represents the matrix transpose. Assume the radar beam is pointing in the following direction: θ0 is the azimuth direction of the beam center in the geodetic coordinate system. If the beam center is in the elevation direction in the geodetic coordinate system, then the direction vector is:

[0062] Based on the above information, the projected velocity of the platform's motion velocity vector in the beam pointing direction is v. d =<v,a0> , where the symbol <·> represents the inner product of two vectors. At this time, the radar beam center receives the ground clutter Doppler center as...

[0063]

[0064] Step 3: Determine the simulated distance range of ground clutter [R] min ,R max ], Azimuth sampling range [θ min ,θ max Given the azimuth sampling interval Δθ, the set of azimuth sampling points is {θ}. m The distance ring set is {R, m = 1, 2, ..., M}. C,n Given the range sampling interval ΔR, where n = 1, 2, ..., N, and the corresponding amplitude of the ground clutter echo signal received by the radar is...

[0065]

[0066] Where λ is the radar signal wavelength, R C Let σ be the distance between the ground object and the radar, and F be the system loss. C σ represents the cross-sectional area of ​​the ground object's radiation. C =ηR·Δθ·ΔR, where η is the scattering coefficient. The elevation angles of ground objects relative to the radar at different range rings correspond to the Doppler frequencies as follows:

[0067]

[0068] Among them, v d,m,n = <v,a m,n >,

[0069] Step 4: To ensure that the Doppler values ​​of the radar received data are not blurred, the radar Doppler resolution should be no less than twice the average Doppler frequency increment of the center distance around the ground features. The specific calculation method is as follows:

[0070] 1) Calculate the Doppler resolution of the radar system

[0071] 2) Calculate the mean Doppler frequency increment of the scattering unit around the center.

[0072]

[0073] in, v c,m = <v,a c,m >, The elevation angle of the ground object relative to the radar is the center distance ring.

[0074] 3) Ensure If the condition is not met, the azimuth sampling interval Δθ should be reduced until the condition is met.

[0075] Step 5: The ground clutter echo signal phase consists of two parts: the phase difference caused by the Doppler frequency due to platform motion and the signal transmission path. The ground clutter phase information of the m-th azimuth sample in the nth range loop is calculated as follows:

[0076]

[0077] The receiver noise signal is

[0078]

[0079] Where k is the Boltzmann constant, T0 is the system noise temperature, and w I (t) and w Q(t) represents the real and imaginary parts of the noise w(t), respectively, which follow a Gaussian distribution N(0,1).

[0080] Ignoring the influence of inter-pulse clutter amplitude fluctuations, the received N range loop echo signals are:

[0081]

[0082] Where k = 1, 2, ..., K represents the number of pulses. n (m) represents the random amplitude, following a Gaussian distribution N(0,1). The transmitted signal... Substitute, and obtain through baseband sampling

[0083]

[0084] Among them, T S =1 / F S The sampling interval is represented by l = 1, 2, ..., TF. S .

[0085] The effectiveness of this invention can be further illustrated by the following computer simulation results:

[0086] The vehicle-mounted radar transmitter sequentially transmits 128 coherent pulse signals within a single CPI, with a pulse repetition period (PRT) of 200µs, a pulse width of 10µs, a signal instantaneous bandwidth of 4MHz, a radar operating frequency of 10GHz, and a peak power of 1000W. The radar array antenna consists of 22×22 elements, with a horizontal and vertical element spacing of 16.7mm, achieving an antenna gain of [missing value]. At this point, the radar's maximum unambiguous range is 30 km, and its range resolution is 37.5 m. The radar baseband transmission waveform is a linear frequency modulated signal.

[0087]

[0088] The vehicle-mounted radar antenna is mounted at a height of 5m, and its velocity vector is v = [0, 10, 0]. T m / s, system loss 5dB, beam center pointing at θ0 = 20° in radar geodetic coordinate system. The azimuth sampling range is [10°, 30°], the distance sampling range is [6.16km, 8.15km], the azimuth sampling interval is 0.25°, the distance sampling interval is 37.5m, and the ground clutter scattering coefficient is -23dB.

[0089] II. Simulation Experiment:

[0090] Under the above simulation conditions, simulation data of ground clutter echo of vehicle-mounted radar during travel provided by the present invention are obtained, and the clutter signal has fluctuation characteristics at different distance cells. Figure 2The blue curve represents the real part of the clutter signal and the red curve represents the imaginary part of the clutter signal, which is simulated using the method provided by this invention in the time domain of a single PRT. Figure 3 This is the compressed data of a single CPI clutter data pulse. Figure 4 The result is obtained by pulse compression and MTD processing of radar clutter data, with the vertical axis representing the normalized Doppler frequency.

[0091] Based on simulation parameters, the radar system's first blind velocity is 75 m / s. According to the radar beam center direction, the platform's projected velocity in the beam direction is approximately 9.4 m / s. Figure 4 It can be seen that the Doppler center of the ground clutter is basically located at around -0.13, which is consistent with the actual result. Furthermore, after MTD processing, the signal energy accumulates near the Doppler center and has a certain spectral width, with inter-pulse coherence of the clutter echo signal within a single CPI. Therefore, the ground clutter modeling and simulation method for vehicle-mounted radar during transit proposed in this invention has certain advantages.

[0092] It should be noted that, as another aspect, this application also provides a storage medium, which may be included in an electronic device or may exist independently without being assembled into the electronic device. The storage medium carries one or more programs, which, when executed by an electronic device, cause the electronic device to perform the methods described in the following embodiments.

[0093] In one embodiment, this application provides a computer program product including a computer program that, when executed by a processor, implements the steps in the above-described method embodiments.

[0094] Furthermore, the above figures are merely illustrative of the processes included in the method according to exemplary embodiments of the present invention, and are not intended to be limiting. It is readily understood that the processes shown in the above figures do not indicate or limit the temporal order of these processes. Additionally, it is readily understood that these processes may be executed synchronously or asynchronously, for example, in multiple modules.

[0095] Other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention herein. This application is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein. The specification and embodiments are to be considered exemplary only, and the true scope and spirit of the invention are indicated by the claims.

[0096] It should be understood that the present invention is not limited to the precise structure described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. A method for modeling and simulating ground clutter while a vehicle-mounted radar is in motion, characterized in that, The method includes: Set the parameters of the vehicle radar so that the vehicle radar emits pulse trains at equal periodic intervals during the journey. Set the motion parameters of the vehicle platform; Ground clutter azimuth and range sampling is performed, and the amplitude of the ground clutter echo signal received by the radar is calculated based on radar parameters. The Doppler frequency is calculated based on the motion parameters of the vehicle platform. The phase of the ground clutter echo signal is calculated based on the Doppler frequency, and the ground clutter echo signal is calculated based on the phase and amplitude of the ground clutter echo signal. To ensure that the Doppler values ​​of the radar received data are not blurred, the radar Doppler resolution should be no less than twice the average Doppler frequency increment of the center distance around the ground features. The specific calculation method is as follows: Calculate the Doppler resolution of a radar system ;in, The number of internal parametric pulses in CPI. The pulse repetition period; Calculate the mean Doppler frequency increment of the scattering unit around the center of the ground object. in, , , , The elevation angle of the ground features relative to the radar at the center distance ring. It is the azimuth angle. Let the platform's velocity vector be... The wavelength of the radar signal; Ensure If this is not met, the azimuth sampling interval should be reduced. Continue until the conditions are met.

2. The method for modeling and simulating ground clutter while the vehicle is in motion, as described in claim 1, is characterized in that... The radar parameters include: Number of phase pulses within CPI Pulse repetition period Pulse width Instantaneous bandwidth of the signal Radar operating frequency Peak power and radar antenna gain .

3. The method for modeling and simulating ground clutter while the vehicle is in motion, as described in claim 1, is characterized in that... The motion parameters of the vehicle platform include the motion velocity vector.

4. The method for modeling and simulating ground clutter while the vehicle is in motion, as described in claim 2, is characterized in that... The calculation of the radar received ground clutter echo signal amplitude based on radar parameters is specifically as follows: in, For radar signal wavelength, For the first n The distance between the ground features and the radar distance. It is system loss; The scattering cross-section of the ground object, The elevation angles of ground features relative to the radar at different ranges are given. The azimuth angle of the azimuth sampling point.

5. The method for modeling and simulating ground clutter while the vehicle is in motion, as described in claim 4, is characterized in that... The calculation of Doppler frequency based on the motion parameters of the vehicle platform is specifically as follows: in, , , The velocity vector of the vehicle platform. This is the motion direction vector of the vehicle platform.

6. The method for modeling and simulating ground clutter while the vehicle is in motion, as described in claim 5, is characterized in that... The calculation of the ground clutter echo signal phase based on Doppler frequency is specifically as follows: 。 7. The method for modeling and simulating ground clutter while the vehicle is in motion, as described in claim 6, is characterized in that... The calculation of the ground clutter echo signal based on the phase and amplitude of the ground clutter echo signal is specifically as follows: in, Indicates the number of pulses. The amplitude is random and follows a Gaussian distribution. , It is Gaussian white noise. To transmit a signal.

8. A storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements the vehicle-mounted radar ground clutter modeling and simulation method as described in any one of claims 1 to 7.

9. A computer program product, comprising a computer program, characterized in that, When the computer program is executed by the processor, it implements the vehicle-mounted radar ground clutter modeling and simulation method according to any one of claims 1 to 7.

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