CN112731390B - Focusing windowing method and application equipment for radar imaging processing - Google Patents
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Abstract
The invention discloses a focusing windowing method and application equipment for radar imaging processing, wherein the method comprises the following steps: acquiring radar echo signals, and constructing an echo data matrix according to the radar echo signals; constructing a translation compensation factor according to the echo data matrix, and performing motion compensation processing on the echo data matrix according to the translation compensation factor to obtain a compensated echo data matrix; determining a windowing function according to focusing processing requirements of radar echo signals, and performing time domain windowing processing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix; wherein the windowing function has a basic form of a power function. According to the invention, the time domain windowing processing is carried out on the radar echo signal based on the windowing function in the form of the power function, so that the focusing performance of each scattering point on a distance-Doppler plane can be effectively enhanced, and the problems of imaging defocusing, tailing, ghosting and the like caused by the conditions of insufficient compensation precision, uneven rotation of a maneuvering target and the like are effectively solved.
Description
Technical Field
The invention relates to the technical field of signal processing, in particular to a focusing windowing method and application equipment for radar imaging processing.
Background
The radar performs two-dimensional high-resolution imaging on a target by using a synthetic aperture radar (Synthetic Aperture Radar, SAR) or an inverse synthetic aperture radar (Inverse Synthetic Aperture Radar, ISAR), and is realized by transmitting a plurality of groups of large time-width-bandwidth product signals to realize high-resolution distance and realizing high-resolution azimuth through relative motion between the radar and the target. Because the transmitted signal has a certain bandwidth, and the first-order or higher-order relative motion between the radar and the target introduces Doppler frequency in the echo spectrum, the echo signal often appears as a higher-order polynomial phase signal (Polynomial Phase Signal, PPS), so that the distance and azimuth spectrum of a single scattering point often has a widening phenomenon. In a classical Range-Doppler (R-D) imaging process, when motion compensation accuracy is insufficient due to inaccurate estimation of motion parameters, one-dimensional image broadening mapping is shown as defocusing of a scattering point in a Range direction and a direction in a Range-Doppler plane, i.e. imaging quality is seriously degraded. In addition, when two-dimensional radar imaging is performed on a maneuvering target, time-varying Doppler introduced by the maneuvering target which rotates unevenly can cause the conventional imaging algorithm to fail, so that serious tailing and other phenomena are caused.
In order to improve the imaging quality, in radar signal processing, the sidelobe amplitudes of the point spread function are typically suppressed by a "windowing" process, so that the resulting image appears smoother and more focused at each scattering point. Conventional window functions typically have "symmetrical" waveforms and "bell-shaped" smoothing characteristics, such as hanning windows, hamming windows, triangular windows, and the like. Due to the sharp sidelobe levels, the focusing performance of the image can be effectively improved; at the same time, however, stronger sidelobe suppression also means an increase in the main lobe width, and therefore these "bell-shaped" conventional windows tend to lose image resolution due to their smoothing effect.
Accordingly, there is a need for improvement and development in the art.
Disclosure of Invention
The invention aims to solve the technical problems of the prior art, provides a focusing windowing method and application equipment for radar imaging processing, and aims to solve the problem that the prior window function can improve the focusing performance of an image and simultaneously lose the resolution of the image due to smoothness.
The technical scheme adopted by the invention for solving the problems is as follows:
in a first aspect, an embodiment of the present invention provides a focusing and windowing method for radar imaging processing, where the method includes:
acquiring radar echo signals, and constructing an echo data matrix according to the radar echo signals;
constructing a translation compensation factor according to the echo data matrix, and performing motion compensation processing on the echo data matrix according to the translation compensation factor to obtain a compensated echo data matrix;
determining a window function according to focusing processing requirements of the radar echo signals, and performing time domain windowing on the compensated echo data matrix according to the window function to obtain a windowed echo data matrix; wherein the windowing function has a power function form.
The focusing windowing method facing radar imaging processing, wherein the step of constructing a translational compensation factor according to the echo data matrix comprises the following steps:
carrying out parameter estimation on the echo data matrix by adopting a parameter estimation method to obtain motion parameters;
and constructing a translational compensation factor according to the motion parameters.
The formula of the translational compensation factor is as follows:
wherein,is translational compensation factor->And f is the instantaneous frequency of the radar echo signal, t is time, and j is an imaginary unit in the complex exponential signal.
The focusing windowing method facing radar imaging processing comprises the following steps:
wherein E is s As a matrix of echo data,is a translational compensation factor, [..]Corresponding multiplications for the elements in the two matrices.
The focusing and windowing method facing radar imaging processing, wherein the step of determining a windowing function according to the focusing processing requirement of the radar echo signal comprises the following steps:
determining a bandwidth convergence ratio according to the focusing processing requirement of the radar echo signal;
determining window function orders corresponding to the windowing functions according to the bandwidth convergence;
and determining a windowing function according to the window function order and the sampling point number of the single observation sequence corresponding to the radar echo signal.
The focusing windowing method facing radar imaging processing comprises the following steps:
where N is the number of sampling points for a single observation sequence and η is the window function order.
The focusing windowing method facing radar imaging processing comprises the following steps:
where N is the number of sampling points for a single observation sequence and η is the window function order.
The focusing windowing method facing radar imaging processing comprises the following steps:
E W (m，：)＝E c (m，：).*h(n)
wherein E is W (m:) is a windowed echo data matrix E W Line m, E c (m:) is the compensated echo data matrix E c H (n) is a windowing function.
The focusing windowing method facing radar imaging processing, wherein the step of performing time domain windowing processing on the compensated echo data matrix by adopting a windowing function to obtain a windowed echo data matrix further comprises the following steps:
and carrying out two-dimensional Fourier transform on the windowed echo data matrix to obtain a focused image.
In a second aspect, the present invention further provides an application device, including:
the construction module is used for acquiring radar echo signals and constructing an echo data matrix according to the radar echo signals;
the compensation module is used for constructing a translational compensation factor according to the echo data matrix, and performing motion compensation processing on the echo data matrix according to the translational compensation factor to obtain a compensated echo data matrix;
the windowing module determines a windowing function according to the focusing processing requirement of the radar echo signal, and performs time domain windowing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix; wherein the windowing function has a power function form.
In a third aspect, embodiments of the present invention further provide a non-transitory computer-readable storage medium, which when executed by a processor of an electronic device, causes the electronic device to perform the radar imaging processing oriented focus windowing method as described in any one of the above.
The invention has the beneficial effects that: firstly, acquiring radar echo signals, constructing an echo data matrix according to the radar echo signals, then constructing a translational compensation factor according to the echo data matrix, performing motion compensation processing on the echo data matrix according to the translational compensation factor to obtain a compensated echo data matrix, finally, determining a windowing function according to focusing processing requirements of the radar echo signals, and performing time domain windowing processing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix; wherein the windowing function has a power function form. According to the invention, the time domain windowing processing is carried out on the radar echo signal based on the window function in the form of the power function, so that the focusing performance of each scattering point on a distance-Doppler plane can be effectively enhanced, and the problems of imaging defocusing, tailing, ghosting and the like caused by the conditions of insufficient compensation precision, uneven rotation of a maneuvering target and the like can be effectively solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are required to be used in the embodiments or the description of the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments described in the present invention, and other drawings may be obtained according to the drawings without inventive effort to those skilled in the art.
FIG. 1 is a schematic flow chart of a focusing and windowing method for radar imaging processing according to an embodiment of the present invention;
FIG. 2 is a graph of a signal spectrum obtained by performing 1-3-order windowing on a Chirp signal using a window function provided by an embodiment of the present invention;
FIG. 3 is a graph showing the variation of the various order window functions with respect to the signal spectrum reception level with the order η;
FIG. 4 is a graph of a signal spectrum of a Chirp signal windowed using a window function in the form of a positive power provided by an embodiment of the present invention;
FIG. 5 is a graph of a signal spectrum of a Chirp signal windowed using a window function in the form of a negative power provided by an embodiment of the present invention;
FIG. 6 is a graph of a signal spectrum of a Chirp signal windowed using a window function and a conventional window function provided by an embodiment of the present invention;
FIG. 7 is a plot of point target imaging contrast results using a window function provided by an embodiment of the present invention and a conventional window function;
FIG. 8 is a graph of overall imaging contrast results for the simulated target corresponding to FIG. 7;
fig. 9 is a functional schematic diagram of an application device according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more clear and clear, the present invention will be further described in detail below with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
It should be noted that, if directional indications (such as up, down, left, right, front, and rear … …) are included in the embodiments of the present invention, the directional indications are merely used to explain the relative positional relationship, movement conditions, etc. between the components in a specific posture (as shown in the drawings), and if the specific posture is changed, the directional indications are correspondingly changed.
In order to improve the imaging quality, in radar signal processing, the sidelobe amplitudes of the point spread function are typically suppressed by a "windowing" process, so that the resulting image appears smoother and more focused at each scattering point. Conventional window functions typically have "symmetrical" waveforms and "bell-shaped" smoothing characteristics, such as hanning windows, hamming windows, triangular windows, and the like. Due to the sharp sidelobe levels, the focusing performance of the image can be effectively improved; at the same time, however, stronger sidelobe suppression also means an increase in the main lobe width, and therefore these "bell-shaped" conventional windows tend to lose image resolution due to their smoothing effect.
In order to solve the problems of the prior art, the embodiment provides a focusing and windowing method for radar imaging processing, by which the focusing performance of each scattering point on a distance-Doppler plane can be effectively enhanced, and the problems of imaging defocusing, tailing, ghosting and the like caused by insufficient compensation precision, uneven rotation of a maneuvering target and the like are effectively improved. In specific implementation, firstly, radar echo signals are acquired, an echo data matrix is constructed according to the radar echo signals, then, a translational compensation factor is constructed according to the echo data matrix, motion compensation processing is carried out on the echo data matrix according to the translational compensation factor, a compensated echo data matrix is obtained, finally, a windowing function is determined according to focusing processing requirements of the radar echo signals, and time domain windowing processing is carried out on the compensated echo data matrix according to the windowing function, so that a windowed echo data matrix is obtained; the window function has a power function form, so that the window function based on the power function form carries out time domain window processing on radar echo signals, the focusing performance of each scattering point on a distance-Doppler plane can be effectively enhanced, and the problems of imaging defocusing, tailing, ghosting and the like caused by insufficient compensation precision, uneven rotation of a maneuvering target and the like are effectively solved.
Exemplary method
The embodiment provides a focusing windowing method for radar imaging processing, which can be applied to an intelligent terminal. As shown in fig. 1, the method includes:
and step S100, acquiring radar echo signals, and constructing an echo data matrix according to the radar echo signals.
Specifically, the radar performs synthetic aperture radar (Synthetic Aperture Radar, SAR) or inverse synthetic aperture radar (Inverse Synthetic Aperture Radar, ISAR) on the targetWhen in dimension high resolution imaging, the distance high resolution is realized by transmitting a plurality of groups of large time-width-bandwidth product signals, and the azimuth high resolution is realized by the relative motion between the radar and the target. In this embodiment, when SAR or ISAR two-dimensional high-resolution imaging is performed on a target by a radar, radar echo signals are acquired according to a signal transceiving mechanism of a radar imaging system. If the number of sampling points of the single observation sequence is N, the obtained radar echo signals can be constructed into a two-dimensional discrete echo data matrix E with the data size of N multiplied by M according to the distance-azimuth dimension s 。
And step 200, constructing a translational compensation factor according to the echo data matrix, and performing motion compensation processing on the echo data matrix according to the translational compensation factor to obtain a compensated echo data matrix.
Since the transmitted signal has a certain spread when the radar is imaged, and the first-order or higher-order relative motion between the radar and the target introduces a doppler frequency in the echo spectrum, the radar echo signal tends to appear as a higher-order polynomial phase signal (Polynomial Phase Signal, PPS). In this embodiment, after an echo data matrix is constructed, a translational compensation factor is constructed according to the echo data matrix, and motion compensation processing is performed on the echo data matrix according to the translational compensation factor, so as to obtain a compensated echo data matrix. The formula of the motion supplementing process is as follows:wherein E is s For echo data matrix>Is a translational compensation factor, [..]Corresponding multiplications for the elements in the two matrices.
In a specific embodiment, the step of constructing the translational compensation factor according to the echo data matrix in step S200 includes:
step S210, carrying out parameter estimation on the echo data matrix by adopting a parameter estimation method to obtain motion parameters;
and step 220, constructing a translational compensation factor according to the motion parameters.
Specifically, in this embodiment, when the translational compensation factor is constructed according to the echo data matrix, a classical parameter estimation method, such as a cross-correlation method, a minimum entropy method, and the like, is first used to perform parameter estimation on the echo data matrix, so as to obtain a motion parameter. And then constructing a translational compensation factor according to the obtained motion parameters. Wherein, the formula of the translational compensation factor is as follows:wherein (1)>Is translational compensation factor->Is a motion parameter, f is the instantaneous frequency of the radar echo signal, t is time, < >>Is the imaginary unit in the complex exponential signal.
Step S300, determining a windowing function according to focusing processing requirements of the radar echo signals, and performing time domain windowing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix; wherein the windowing function has a power function form.
Considering conventional window functions such as hanning windows, hamming windows, triangular windows, etc., have "symmetrical" waveforms and "bell-shaped" smoothing characteristics that improve image focusing while losing image resolution due to smoothing. The present embodiment proposes a new windowing technique, in general, a window function is defined as having normalized non-zero terms within a closed interval, in the form:
wherein, h n is more than or equal to 0 and less than or equal to 1, N is the signal length.
Referring to the definition form of the window function, the window function proposed in this embodiment is normalized η power function (η is a natural number) within the time t e [0, t ], and the expression of the window function and its antisymmetric form is:
based on the above formula (2), the expression of the η -order normalized window function in discrete form and its antisymmetric form is further defined as:
after determining the windowing function, the embodiment further performs time domain windowing processing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix. Compared with the symmetrical waveform and bell-shaped smooth characteristic of the conventional window function, the window function provided by the embodiment has the asymmetric wedge-shaped sharpening characteristic, can effectively enhance the focusing property of each scattering point on a distance-Doppler plane, and effectively improve the problems of imaging defocusing, tailing, ghost and the like caused by the conditions of insufficient compensation precision, uneven rotation of a maneuvering target and the like.
To further illustrate the focused windowing effect of the window function presented in this embodiment on radar imaging processing, the inventors take the form of the primary signal in radar imaging processing as an example, using the window function presented in this embodiment on a single-component Chirp signal (i.e., chirp signal) And (5) windowing. The expression of the single-component linear frequency modulation pulse signal is as follows:wherein (1)>K is the imaginary unit in the complex exponential signal 1 Is the angular frequency, k of the signal 2 Is the frequency modulation rate of the signal, and k 2 ≠0。
When the window function order η=1, the frequency spectrum function after the window processing is performed on the single-component chirp signal by using the window function proposed in the present embodiment is:
wherein,x is a Fourier transform operator 0 And (omega) is a signal obtained by performing Fourier transform on the single-component chirp signal.
As can be seen from the above equation (4), the spectrum obtained by first-order windowing the single-component Chirp signal corresponds in form to the original spectrum X of the signal 0 (omega) amplitude modulation of the primary function. The slope of the modulation function A (ω) depends on the angular modulation frequency k of the Chirp signal 2 The zero position of the modulation function on the frequency axis corresponds to the initial angular frequency k of the Chirp signal 1 。
When the window function order η > 1, the frequency spectrum function after the window processing is performed on the single component chirp signal by using the window function provided in the present embodiment is:
the following recursive relationship exists in the above formula (5):
when η=0 in equation (6), a spectrum function obtained by performing the second-order windowing on the single-component Chirp signal is:
X 2 (ω)＝[A 2 (ω)+C]·X 0 (ω)+B(ω)[A(ω)+T]+C·A(ω) (7)
as can be seen from the above equation (7), the second order windowed spectrum of the single-component Chirp signal is obtained by modulating its original spectrum via a quadratic function. Further to the general situation, the spectrum expression obtained after the eta-order window function windowing is carried out on the single-component Chirp signal is as follows:
X η (ω)＝Λ η (ω)·X 0 (ω)+γ(ω) (8)
wherein gamma (omega) is the lower order margin of the eta-order windowed signal spectral function, which has no effect on the overall envelope shape of the spectrum, Λ η (omega) is the core modulation function,
from the above analysis, it can be seen that the windowing of a wideband signal in the form of a Chirp signal by an η -order window function results in a spectral function corresponding to the modulation of the waveform by an η power of the original spread spectrum of the signal. FIG. 2 shows a Chirp signal example x (t) =exp (-j 2. Pi. 20t+j2pi.8t) 2 ) The original frequency spectrum of the signal and the frequency spectrum shape of the signal after 1-3-order windowing treatment are carried out, wherein the initial frequency of the signal is 20Hz, the pulse time width is tau=2.5 s, and the sampling point number is N s =256. As can be seen from fig. 2, PPS signals such as Chirp signals have a certain frequency bandwidth due to the high-order time-varying characteristic of the phase, which is not beneficial to the envelope alignment of single-component signals. In contrast, the frequency spectrum subjected to windowing presents a sharper single peak, highlights the strongest jump point in the frequency component, and is very beneficial to signal alignment. From a physical perspective, the window function proposed in this embodiment has a time-frequency that is complexThe broadened spectrum of the signal is sharpened to the characteristic of a "wedge" unimodal envelope such that the energy of the signal is concentrated at the edges of the spectrum as the only spike and the higher the power the more concentrated the sharpened envelope shape is concentrated.
Keeping the fourier spectrum bandwidth of the original signal as B, if the widths of the window function converging waveforms with different orders are defined at the median position (the normalized amplitude intensity is 0.5 corresponds to-3 dB bandwidth) shown in fig. 2, the median width of the signal spectrum after η -order windowing can be obtained as follows:the degree of sharpening of the signal spectrum by the window function is described by a normalized bandwidth convergence ratio (Normalized Bandwidth Convergence Ratio, NBCR), which is the ratio of the width of the spectrum (median line) to the width of the original signal spectrum after η -order windowing of the wideband signal, recorded asFig. 3 is a graph showing the variation of the signal spectrum convergence degree with the order η of each order window function, and it can be seen from fig. 3 that when η=0, the signal spectrum is consistent with the original spectrum, and the convergence ratio is 1; when going to infinity, the convergence ratio tends to be 0, i.e. the spectral width of the signal tends to be zero, the spectrum will gradually converge to a sprint function. From the enlarged detail view, it can be seen that the 1 st order window function can converge the wideband spectrum of the signal to half, the 2 nd order window function can converge the wideband spectrum of the signal to 1/3, and the signal spectrum processed by the 3 rd order window function is converged to only one single peak with the 1/5 of the original spectrum width.
Further, as can be seen from the above formula (3), the window function in the present embodiment is an irregular window function of an asymmetric form including a positive-power form and a negative-power form, that is, an antisymmetric form. As shown in fig. 4 and 5, the signal spectrum diagram of the Chirp signal is obtained after the window function in the form of positive power and the window function in the form of negative power are processed. From fig. 4 and fig. 5, it can be seen that, from the window function, both forms of window functions filter out the frequency position with the strongest signal amplitude, and take this position as the center, to converge the signal energy into a lobe with a narrower bandwidth than the original bandwidth. From the focusing effect, the window functions of the two forms are the same; the difference between the two forms of window functions is only that the edge positions for sharpening the signal spectrum are different, and the difference between the edge positions can be corrected by carrying out unified spectrum offset processing according to the signal bandwidth in an imaging calibration link.
In a specific embodiment, the step of determining the windowing function according to the focusing processing requirement of the radar echo signal in step S300 includes:
step S310, determining a bandwidth convergence ratio according to the focusing processing requirement of the radar echo signal;
step 320, determining the window function order corresponding to the windowing function according to the bandwidth convergence;
step S330, determining a windowing function according to the window function order and the number of sampling points of the single observation sequence corresponding to the radar echo signal.
As can be seen from the above formula (3), the windowing function provided in this embodiment is determined by the window function order η, when determining the windowing function, the normalized bandwidth convergence ratio is set according to the actual requirement of the user for the wideband signal spectrum convergence, and then the window function order corresponding to the windowing function is determined according to the preset bandwidth convergence ratio. Wherein, the formula of the window function order is:wherein eta is the order of a window function, R is the bandwidth convergence ratio, and R is more than 0 and less than 1.
Further, as mentioned in step S100, the radar echo signal is collected according to the observation sequence transmitted by the radar in the observation accumulation time and the sampling point number of the single observation sequence, where the sampling point number of the single observation sequence is the sampling point number of the single observation sequence corresponding to the radar echo signal. After determining the window function order corresponding to the windowing function, determining the windowing function according to the window function order and the sampling point number of the single observation sequence corresponding to the radar echo signal. Wherein the windowing function is a common formulaThe formula is:where N is the number of sampling points for a single observation sequence and η is the window function order.
The order variability is one of the important characteristics of the window function proposed in this embodiment, but it does not mean that the better the spectral width of the signal is converged by the window function of higher power, because the "windowing" process inevitably reduces some frequency components of the signal, and the reduction of the spectrum necessarily reduces the energy of the signal itself to some extent. To measure the impact of the windowing process on signal energy, the inventors describe the degree of loss of signal power or energy by coherent power gain. In a visual sense, the gain degree can be understood as a proportional relation between the frequency spectrum after being windowed and the area surrounded by the original frequency spectrum of the signal and the frequency axis in fig. 2, and the coherent power gain corresponding to the η -order window function can be expressed as:
from the above equation (9), it is known that the coherent power gain after the eta-order windowing process is inversely proportional to the power of 2 eta of the Chirp modulation frequency, i.e.Therefore, selecting the appropriate window function order is important to achieve both signal spectrum focusing and signal energy conservation. Considering the focusing requirement on the signal spectrum and the energy requirement of the signal overall, a more suitable windowed power is η=1 to 3.
FIG. 6 is a graph of a signal spectrum of a Chirp signal windowed using a window function and a conventional window function provided by an embodiment of the present invention, where it can be seen from FIG. 6 that the conventional window function has a "smoothing" effect on the signal spectrum, and the windowed signal spectrum exhibits a centrally focused "bell-shaped" response; in contrast, the window function in the invention can be regarded as a wedge-shaped band-pass filter with sharp edges, and the window function acts on the signal spectrum to sharpen sharp frequency conversion points on two sides (one side) of the frequency band and filter out the broadening components of the frequency spectrum, so that the window function has the characteristic of wedging single peak on the broadband signal spectrum and can sharply highlight the frequency position where amplitude jump occurs on the edge. The window functions of the two classes are each long in different signal processing scenarios. In the signal processing field facing ISAR imaging, insufficient compensation caused by insufficient parameter estimation precision or high-order rotation existing in the target can lead to the spectrum broadening of each component of the target echo, and the spectrum broadening is reflected on a two-dimensional image, namely defocusing and blurring. In this case, the unconventional window function provided by the invention can better solve the defocus problem and improve the signal spectrum and the focusing property of imaging.
And step 400, performing two-dimensional Fourier transform on the windowed echo data matrix to obtain a focused image.
Specifically, after the windowed echo data matrix is obtained in this embodiment, a two-dimensional fourier transform is further performed on the windowed echo data matrix, so as to perform a distance-azimuth two-dimensional compression process on the windowed echo data matrix, and obtain an image with better focusing. The formula for performing two-dimensional Fourier transform on the windowed echo data matrix is as follows: i=fft2 (E W )。
In order to verify the imaging effect of the scheme of the invention, an application example of ISAR imaging of an airplane by using a radar is described, and a simulation design target has high-order rotation parameters w1=0.1 rad/s and ω2= -0.04rad/s 2 Taking the 67 th scattering point in the target as a single scattering point target, FIG. 7 shows the point target imaging comparison result graphs of the windowed, 8 conventional window functions and 1-3 order window functions, and FIG. 8 is the corresponding simulation target overall imaging comparison result graph. From fig. 7 and 8, the following conclusions can be drawn: (1) Because the non-uniform rotation characteristic of the target generates time-varying Doppler, serious azimuth defocusing occurs when imaging is not performed, and particularly, the positions of a nose, a wing, a tail and the like which are far away from the center of a phase have obvious trailing phenomena; (2) The various windowing processes enhance the focusing of the scattering points to varying degrees, but almost all conventional windows do not effectively address the target edgesProblems with scattering tails; (3) Compared with a conventional window function, the image processed by the window function has obvious focusing effect, particularly, the 2-order and 3-order window functions focus the points of the image very intensively, thereby effectively improving the tailing phenomenon, enhancing the imaging details and being very beneficial to target identification. Therefore, the windowing method provided by the invention has very practical application significance for the frequency spectrum broadening phenomenon and the image defocusing condition generated by the complex motion of the target in the radar imaging processing.
Exemplary apparatus
Based on the above embodiment, the present invention also provides an application device, and a functional schematic diagram thereof is shown in fig. 9. The application device includes a build module 110, a compensation module 120, and a windowing module 130.
The construction module 110 is configured to acquire a radar echo signal, and construct an echo data matrix according to the radar echo signal;
the compensation module 120 is configured to construct a translational compensation factor according to the echo data matrix, and perform motion compensation processing on the echo data matrix according to the translational compensation factor, so as to obtain a compensated echo data matrix;
the windowing module 130 is configured to determine a windowing function according to a focusing processing requirement of the radar echo signal, and perform time domain windowing processing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix; wherein the windowing function has a power function form.
Those skilled in the art will appreciate that implementing all or part of the above described methods may be accomplished by way of a computer program stored on a non-transitory computer readable storage medium, which when executed, may comprise the steps of the embodiments of the methods described above. Any reference to memory, storage, database, or other medium used in embodiments provided herein may include non-volatile and/or volatile memory. The nonvolatile memory can include Read Only Memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), memory bus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), among others.
In summary, the invention discloses a focusing windowing method and application equipment for radar imaging processing, wherein the method comprises the following steps: acquiring radar echo signals, and constructing an echo data matrix according to the radar echo signals; constructing a translation compensation factor according to the echo data matrix, and performing motion compensation processing on the echo data matrix according to the translation compensation factor to obtain a compensated echo data matrix; determining a windowing function according to focusing processing requirements of the radar echo signals, and performing time domain windowing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix; wherein the windowing function has a power function form. Compared with the symmetric waveform and bell-shaped smooth characteristic of the conventional window function, the window function provided by the invention has the asymmetric wedge-shaped sharpening characteristic, can effectively enhance the focusing property of each scattering point on a distance-Doppler plane, and effectively improve the problems of imaging defocusing, tailing, ghost and the like caused by insufficient compensation precision, uneven rotation of a maneuvering target and the like.
It is to be understood that the invention is not limited in its application to the examples described above, but is capable of modification and variation in light of the above teachings by those skilled in the art, and that all such modifications and variations are intended to be included within the scope of the appended claims.
Claims (6)
1. A radar imaging processing-oriented focusing windowing method, the method comprising:
acquiring radar echo signals, and constructing an echo data matrix according to the radar echo signals;
constructing a translation compensation factor according to the echo data matrix, and performing motion compensation processing on the echo data matrix according to the translation compensation factor to obtain a compensated echo data matrix;
determining a windowing function according to focusing processing requirements of the radar echo signals, and performing time domain windowing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix; wherein the windowing function has a power function form;
the step of determining a windowing function according to the focusing processing requirement of the radar echo signal comprises the following steps:
determining a bandwidth convergence ratio according to the focusing processing requirement of the radar echo signal;
determining window function orders corresponding to the windowing functions according to the bandwidth convergence;
determining a windowing function according to the window function order and the sampling point number of the single observation sequence corresponding to the radar echo signal;
the formula of the windowing function is as follows:
wherein,Nthe number of sampling points for a single observation sequence,order for window function;
the anti-symmetric form of the windowing function is:
wherein,Nthe number of sampling points for a single observation sequence,order for window function;
the formula of the time domain windowing processing is as follows:
wherein,for a windowed echo data matrix +.>Is the first of (2)mThe number of rows of the device is,E c (mfor a compensated echo data matrixE c Is the first of (2)mThe number of rows of the device is,h(n) Is a windowing function.
2. The radar imaging processing oriented focusing windowing method as in claim 1, wherein said step of constructing a translational compensation factor from said echo data matrix comprises:
carrying out parameter estimation on the echo data matrix by adopting a parameter estimation method to obtain motion parameters;
and constructing a translational compensation factor according to the motion parameters.
3. The radar imaging processing oriented focusing windowing method as in claim 2, wherein said translational compensation factor is formulated as:
wherein,is translational compensation factor->For exercise parameters->For the instantaneous frequency of the radar return signal,tj is the imaginary unit in the complex exponential signal for time.
4. The radar imaging processing oriented focusing windowing method as in claim 1, wherein said motion compensation processing is formulated as:
wherein,for echo data matrix>Is a translational compensation factor, [..]Corresponding multiplications for the elements in the two matrices.
5. The radar imaging processing-oriented focusing windowing method as in claim 1, wherein said step of performing time-domain windowing on said compensated echo data matrix using a windowing function to obtain a windowed echo data matrix further comprises:
and carrying out two-dimensional Fourier transform on the windowed echo data matrix to obtain a focused image.
6. A radar imaging processing-oriented focused windowing application device, comprising:
the construction module is used for acquiring radar echo signals and constructing an echo data matrix according to the radar echo signals;
the compensation module is used for constructing a translational compensation factor according to the echo data matrix, and performing motion compensation processing on the echo data matrix according to the translational compensation factor to obtain a compensated echo data matrix;
the windowing module is used for determining a windowing function according to the focusing processing requirement of the radar echo signal, and performing time domain windowing on the compensated echo data matrix according to the windowing function to obtain a windowed echo data matrix; wherein the windowing function has a power function form;
the windowing module is further configured to:
determining a bandwidth convergence ratio according to the focusing processing requirement of the radar echo signal;
determining window function orders corresponding to the windowing functions according to the bandwidth convergence;
determining a windowing function according to the window function order and the sampling point number of the single observation sequence corresponding to the radar echo signal;
the formula of the windowing function is as follows:
wherein,Nthe number of sampling points for a single observation sequence,order for window function;
the form of symmetry inversion of the windowing function is:
wherein,Nthe number of sampling points for a single observation sequence,order for window function;
the formula of the time domain windowing processing is as follows:
wherein,for a windowed echo data matrix +.>Is the first of (2)mThe number of rows of the device is,E c (mfor a compensated echo data matrixE c Is the first of (2)mThe number of rows of the device is,h(n) Is a windowing function.
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