Modeling and simulation method for ground clutter during travel of vehicle-mounted radar

Abstract

The invention particularly relates to a method for modeling and simulating ground clutters during traveling of a vehicle-mounted radar, which comprises the following steps of: setting parameters of the vehicle-mounted radar, so that the vehicle-mounted radar transmits pulse strings at equal period intervals in the traveling process; setting motion parameters of the vehicle-mounted platform; carrying out ground clutter azimuth and distance sampling, calculating the amplitude of ground clutter echo signals received by a radar based on radar parameters, and calculating Doppler frequency based on vehicle-mounted platform motion parameters; and calculating a ground clutter echo signal phase based on the Doppler frequency, and calculating a ground clutter echo signal based on the ground clutter echo signal phase and the ground clutter echo signal amplitude. According to the method, the influence of various factors such as the radar working frequency, the radar erection height, the beam pointing, the beam gain, the signal bandwidth and the platform motion on the ground clutter echo is fully considered, simulation modeling is carried out on the radar ground clutter echo signal in a single CPI, and simulation data are closer to a real scene.

Description

Technical Field

[0001] The present invention relates to the field of radar technology, and in particular to a method for modeling and simulating ground clutter of a moving vehicle-mounted radar, which is suitable for simulating a complex working environment of the vehicle-mounted radar. Background Art

[0002] Vehicle-mounted reconnaissance radar mainly detects targets such as personnel, vehicles and low-altitude aircraft on the ground. Due to the particularity of its working environment, it is mainly interfered by ground clutter during the detection of targets. The clutter components in the echo data have complex characteristics, and their amplitude characteristics and pulse correlation will be different from the characteristics of conventional single-type clutter. In scientific research and engineering applications, radar workers often use simulated data to replace field test data due to the difficulty of control, poor repeatability, and requirements for manpower, material resources, and financial resources in field tests. The key to the quality of the clutter model lies in whether it can realistically simulate the relevant characteristics of clutter in the actual test environment. Excellent clutter models often act as clutter signal sources in radar systems, providing clutter basis for the research and development and upgrading of radar signal processing systems. In addition to being more conducive to radar simulator designers to establish a more ideal radar system model, it is also beneficial for signal workers to have a deep understanding of the characteristics of various signal processing methods, provide theoretical support for related design decisions, and combine specific technologies to maximize the elimination of the adverse effects of clutter interference on the working performance of related radar products.

[0003] People have done a lot of research and experiments on clutter characteristics, and established a variety of statistical models to further analyze the formation mechanism of clutter. Among them, the common clutter amplitude distribution models are: Rayleigh distribution, Weibull distribution, log-normal distribution and K distribution. When the clutter of the radar mainly comes from meteorological interference or the radar resolution is low, the clutter envelope obeys the Rayleigh distribution. Rayleigh distribution is an extreme distribution, and the distribution is mainly affected by a single parameter. At the same time, the distribution can be derived from the central limit theorem in theory. Since the Rayleigh distribution has the shortest tail and the in-phase and orthogonal components of the clutter both satisfy the Gaussian sequence, it is also called Gaussian clutter. The existing clutter simulation methods mainly include zero memory nonlinear transformation method (ZMNL) and spherically invariant random process method (SIRP). The ZMNL method is a process in which a non-correlated Gaussian sequence is transformed into a correlated Gaussian sequence, and then a certain nonlinear change is found to become a correlated non-Gaussian sequence. The SIRP method is used to generate clutter data. The probability density function characteristics and power spectrum density function characteristics of the clutter data can be independently controlled and are not affected by each other, which is conducive to generation.

[0004] The above clutter simulation methods are essentially to 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. In addition, the correlation of clutter echoes within a single CPI cannot be achieved, resulting in the inability of traditional methods to truly simulate the ground clutter echo signals of radars under vehicle-mounted platforms.

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

[0006] The present invention provides a method for modeling and simulating ground clutter of a vehicle-mounted radar while it is moving, which takes into account the influence of radar parameters on clutter echoes and can more realistically simulate ground clutter echo signals of the radar under a vehicle-mounted platform.

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

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

[0009] Set the vehicle platform motion parameters;

[0010] Sampling the ground clutter azimuth and distance, calculating the amplitude of the ground clutter echo signal received by the radar based on the radar parameters, and calculating the Doppler frequency based on the vehicle platform motion parameters;

[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 of the ground clutter echo signal and the 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 vehicle-mounted platform motion parameter includes a motion velocity vector.

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

[0016]

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

[0018] In some exemplary embodiments, the calculation of the Doppler frequency based on the vehicle-mounted platform motion parameters is specifically as follows:

[0019]

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

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

[0022] In order to ensure that the Doppler dimension of the radar received data is not ambiguous, the azimuth sampling interval should be reasonably selected to ensure that the radar Doppler resolution is not less than twice the mean value of the Doppler frequency increment around the center distance of the ground object.

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

[0024]

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

[0026]

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

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

[0029] According to a third aspect of the present invention, there is provided a computer program product having a computer program stored thereon, and when the computer program is executed by a processor, the method for modeling and simulating ground clutter of a moving vehicle-mounted radar as described in the first aspect is implemented.

[0030] The embodiment of the present invention provides a method for modeling and simulating ground clutter of a vehicle-mounted radar during movement. The method performs simulation modeling based on the actual working scene of the vehicle-mounted battlefield reconnaissance radar, fully considers the influence of multiple factors such as radar operating frequency, radar height, beam pointing, beam gain, signal bandwidth and platform motion on ground clutter echo, and simulates and models the radar ground clutter echo signal within a single CPI. The simulated data is closer to the real scene. The vehicle-mounted radar transmits a pulse train at equal periodic intervals during the movement process, which is received by the radar after being reflected by the ground object. The radar signal processor then performs MTD filtering on the received echo signal to improve the radar detection performance.

[0031] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings herein are incorporated into and constitute a part of the specification, illustrate embodiments consistent with the present invention, and together with the specification are used to explain the principles of the present invention. Obviously, the accompanying drawings described below are only some embodiments of the present invention, and for those of ordinary skill in the art, other accompanying drawings can be obtained based on these accompanying drawings without creative work.

[0033] Figure 1 A flow chart of a method for modeling and simulating ground clutter of a moving vehicle-mounted radar provided in an embodiment of the present invention.

[0034] Figure 2 The present invention provides a method for simulating single pulse ground clutter time domain echo data.

[0035] Figure 3 The echo data after compression of a single CPI internal clutter pulse is obtained by simulation using the method provided by the present invention.

[0036] Figure 4 The MTD post-echo data of the clutter in a single CPI is simulated by the method provided by the present invention. DETAILED DESCRIPTION

[0037] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in many forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that the present invention will be more comprehensive and complete and fully convey the concepts of the example 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] In addition, the accompanying drawings are only schematic illustrations of the present invention and are not necessarily drawn to scale. The same reference numerals in the figures represent the same or similar parts, and their repeated description will be omitted. Some of the block diagrams shown in the accompanying drawings are functional entities and do not necessarily correspond to physically or logically independent entities. These functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices.

[0039] The embodiment of the present invention provides a method for modeling and simulating ground clutter of a vehicle-mounted radar while it is moving. The present invention performs simulation modeling based on the actual working scene of the vehicle-mounted battlefield reconnaissance radar, fully considers the influence of multiple factors such as radar operating frequency, radar height, beam pointing, beam gain, signal bandwidth and platform motion on ground clutter echo, and simulates and models the radar ground clutter echo signal within a single CPI, so that the simulated data is closer to the real scene. The vehicle-mounted radar transmits a pulse train at equal periodic intervals during the moving process, which is received by the radar after being reflected by the ground object, and the radar signal processor then performs MTD filtering on the received echo signal to improve the radar detection performance. In order to restore the real scene, the simulation model established by the present invention: 1) considers the influence of sidelobe clutter on the basis of mainlobe clutter; 2) the intensity of ground clutter echo at different distances is affected by antenna gain and radar equation; 3) considering the influence of the moving platform, the Doppler center of the ground clutter is not at zero frequency, and the frequency center is related to the beam pointing and the movement speed of the vehicle-mounted platform.

[0040] Figure 1 A flow chart of a method for modeling and simulating ground clutter of a vehicle-mounted radar during movement provided by 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 of vehicle-mounted motion platform parameters: platform motion velocity vector v, assuming that the radar beam is pointing to θ0 is the azimuth of the beam center in the geodetic coordinate system, is the beam center elevation direction in the geodetic coordinate system, then the direction vector is

[0043] According to the above information, the projection speed of the platform 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 Doppler center of the ground clutter wave received by the radar beam center is

[0044]

[0045] Where λ is the wavelength of the radar signal.

[0046] Step 3: Assume that the set of azimuth sampling points is {θ m ,m=1,2,…,M}, the distance ring set is {R C,n ,n=1,2,…,N}, the corresponding radar receives the ground clutter echo signal amplitude is

[0047]

[0048] Among them, R C is the distance between the object and the radar, and F is the system loss. C is the ground object scattering cross-sectional area, and its corresponding Doppler frequency is

[0049]

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

[0051] Step 4: To ensure that the Doppler dimension of radar received data is not ambiguous, the azimuth sampling interval Δθ should be reasonably selected to ensure that the radar Doppler resolution is not less than twice the mean value of the Doppler frequency increment around the center distance of the object.

[0052] Step 5: Calculate the ground clutter phase information of the mth azimuth sampling of the nth range loop as follows:

[0053]

[0054] Without considering the influence of the fluctuation of the clutter amplitude between pulses, the received N range loop echo signals are

[0055]

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

[0057] Below, each step of the phased array radar design method in this example implementation will be described in more detail with reference to the accompanying drawings and embodiments.

[0058] Step 1: In a 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, is the pitch angle. At this time, the maximum unambiguous distance of the radar is Radar range resolution c is the speed of light. Assume that the radar baseband transmission waveform is a linear frequency modulation signal:

[0059]

[0060] in, is the frequency modulation slope. The baseband sampling frequency is F s , requiring the baseband sampling frequency to be F s Satisfies the Nyquist sampling theorem, that is, F s ≥2B.

[0061] Step 2: Simulation settings of vehicle motion platform parameters: platform motion velocity vector v = [v x ,v y ,v z ] T , where v x , v y , v z Represents east speed, north speed and sky speed respectively, [·] T represents the matrix transpose. Assume that the radar beam is pointing to θ0 is the azimuth of the beam center in the geodetic coordinate system, is the beam center elevation direction in the geodetic coordinate system, then the direction vector is

[0062] According to the above information, the projection speed of the platform 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 Doppler center of the ground clutter wave received by the radar beam center is

[0063]

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

[0065]

[0066] Where λ is the wavelength of the radar signal, R C is the distance between the object and the radar, and F is the system loss. C is the ground object scattering cross-sectional area. C =ηR·Δθ·ΔR, η is the scattering coefficient. is the elevation angle of the ground object relative to the radar at different distance rings, and the corresponding Doppler frequency is

[0067]

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

[0069] Step 4: To ensure that the Doppler dimension of radar received data is not ambiguous, the radar Doppler resolution should be no less than twice the mean value of the Doppler frequency increment of the center distance ring object. The specific calculation method is as follows:

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

[0071] 2) Calculate the mean value of the Doppler frequency increment of the center distance ring ground object scattering unit

[0072]

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

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

[0075] Step 5: The phase of the ground clutter echo signal consists of two parts: the Doppler frequency caused by the platform motion and the phase difference caused by the signal transmission path. The ground clutter phase information of the mth azimuth sampling of the nth range loop is calculated as

[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) are the real and imaginary parts of the noise w(t), respectively, which obey the Gaussian distribution N(0,1).

[0080] Without considering the influence of the fluctuation of the clutter amplitude between pulses, the received N range loop echo signals are

[0081]

[0082] Where k = 1, 2, ..., K represents the number of pulses. n (m) is the random amplitude, which follows the Gaussian distribution N(0,1). Substituting in, we get after baseband sampling

[0083]

[0084] Among them, T S =1 / F S Represents the sampling interval, l=1,2,…,TF S .

[0085] The effect of the present invention can be further illustrated by the following computer simulation experimental results:

[0086] The vehicle-mounted radar transmitter transmits 128 coherent pulse signals in sequence within a single CPI, with a pulse repetition period (PRT) of 200us, a pulse width of 10us, 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 array elements, with horizontal and vertical array element spacing of 16.7mm, and the antenna gain is At this time, the maximum unambiguous distance of the radar is 30km, and the radar distance resolution is 37.5m. The radar baseband transmission waveform is a linear frequency modulation signal:

[0087]

[0088] The vehicle-mounted radar antenna is 5m high, and the velocity vector is v=[0,10,0] T m / s, system loss 5dB, the beam center pointing in the radar geodetic coordinate system is θ0=20°, 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] 2. Simulation experiment:

[0090] Under the above simulation conditions, the simulation data of the clutter echo of the vehicle-mounted radar during movement of the method provided by the present invention is obtained, and the clutter signal has an undulating characteristic in different distance units. Figure 2The time-domain ground clutter echo data in a single PRT simulated by the method provided by the present invention is shown in FIG. 1 . The blue curve represents the real part of the clutter signal, and the red curve represents the imaginary part of the clutter signal. Figure 3 It is the data after pulse compression of noise data in a single CPI. Figure 4 It is the result obtained by MTD processing after pulse compression of radar received clutter data, and the vertical axis is the normalized Doppler frequency.

[0091] According to the simulation parameters, the first blind speed of the radar system is 75m / s. According to the center direction of the radar beam, the projection speed of the platform in the direction of the beam is about 9.4m / s. Figure 4 It can be obtained that the Doppler center of the ground clutter is basically located at about -0.13, and the simulation results are consistent with the actual results. In addition, after MTD processing, the signal energy accumulates near the Doppler center and has a certain spectrum width, and the clutter echo signal pulses in a single CPI are coherent. Therefore, the ground clutter modeling and simulation method proposed by the present invention for the vehicle-mounted radar during movement has certain advantages.

[0092] It should be noted that, as another aspect, the present 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 above storage medium carries one or more programs, and when the above one or more programs are executed by an electronic device, the electronic device implements the method described in the following embodiments.

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

[0094] In addition, the above-mentioned figures are only schematic illustrations of the processes included in the method according to an exemplary embodiment of the present invention, and are not intended to be limiting. It is easy to understand that the processes shown in the above-mentioned figures do not indicate or limit the time sequence of these processes. In addition, it is also easy to understand that these processes can be performed synchronously or asynchronously, for example, in multiple modules.

[0095] Other embodiments of the invention will readily occur to those skilled in the art after considering the specification and practicing 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 that are not disclosed by the present invention. The specification and examples 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 exact construction that has been described above and shown in the drawings and that various modifications and changes may be made without departing from the scope thereof. The scope of the present invention is limited only by the appended claims.

Claims

1. A method for modeling and simulating ground clutter of a vehicle-mounted radar while traveling, characterized in that: The method comprises: Set the vehicle radar parameters so that the vehicle radar transmits pulse trains at equal periodic intervals during the moving process; Set the vehicle platform motion parameters; Sampling the ground clutter azimuth and distance, calculating the amplitude of the ground clutter echo signal received by the radar based on the radar parameters, and calculating the Doppler frequency based on the vehicle platform motion parameters; 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 of the ground clutter echo signal and the amplitude of the ground clutter echo signal.

2. The method for modeling and simulating ground clutter of a vehicle-mounted radar according to claim 1, characterized in that: The radar parameters include: 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 3. The method for modeling and simulating ground clutter of a vehicle-mounted radar while traveling according to claim 1, characterized in that: The vehicle-mounted platform motion parameters include a motion velocity vector.

4. The method for modeling and simulating ground clutter of a vehicle-mounted radar according to claim 3, characterized in that: The calculation of the radar receiving ground clutter echo signal amplitude based on radar parameters is specifically as follows: Where λ is the wavelength of the radar signal, R C,n is the distance between the object and the radar, F is the system loss; σ C is the ground scattering cross-sectional area, is the elevation angle of the ground object relative to the radar at different distance rings, θ m is the azimuth of the azimuth sampling point.

5. The method for modeling and simulating ground clutter of a vehicle-mounted radar while traveling according to claim 4, characterized in that: The vehicle-mounted platform motion parameter calculates the Doppler frequency, specifically: Among them, v d,m,n =v,a m,n , v is the velocity vector of the vehicle platform, a m,n is the moving direction vector of the vehicle-mounted platform.

6. The method for modeling and simulating ground clutter of a vehicle-mounted radar while traveling according to claim 1, characterized in that: The method further comprises: In order to ensure that the Doppler dimension of the radar received data is not ambiguous, the azimuth sampling interval should be reasonably selected to ensure that the radar Doppler resolution is not less than twice the mean value of the Doppler frequency increment around the center distance of the ground object.

7. The method for modeling and simulating ground clutter of a vehicle-mounted radar while traveling according to claim 5, characterized in that: The phase of the ground clutter echo signal is calculated based on the Doppler frequency, specifically:

8. The method for modeling and simulating ground clutter of a vehicle-mounted radar while traveling according to claim 7, characterized in that: The ground clutter echo signal is calculated based on the ground clutter echo signal phase and the ground clutter echo signal amplitude, specifically: Where k = 1, 2, ..., K represents the number of pulses, z n (m) is the random amplitude, which follows the Gaussian distribution N(0,1), and w(t) is Gaussian white noise.

9. A storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the method for modeling and simulating ground clutter of a moving vehicle-mounted radar according to any one of claims 1 to 8 is implemented.

10. A computer program product, comprising a computer program, characterized in that When the computer program is executed by a processor, the method for modeling and simulating ground clutter of a moving vehicle-mounted radar according to any one of claims 1 to 8 is implemented.

Images