Step frequency inverse synthetic aperture radar (ISAR) imaging method based on coherent processing
A technology of stepping frequency and imaging method, which is applied in the field of radar, and can solve problems such as low computing efficiency, large estimation error, and affecting sub-pulse coherence
Active Publication Date: 2014-07-09
XIDIAN UNIV
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[0005] 1. The minimum entropy method needs to use the search method to estimate the motion parameters, the search step size is difficult to control, and the operation efficiency is low
[0006] 2. Fitting the motion parameters of the target through the movement of the echo envelope, the estimation error is large, and the residual phase error is also large, which seriously affects the coherence between the sub-pulses in the pulse group and makes the synthesized target image appear Phenomenon of main lobe broadening and side lobe deterioration
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[0037] The present invention will be further described below in conjunction with the drawings.
[0038] Reference figure 1 The specific implementation steps of the present invention are as follows:
[0039] Step 1. Establish a stepped frequency ISAR echo signal model.
[0040] Suppose the waveform of the linear frequency modulation step signal transmitted by the radar is:
[0041] U(t)=u 1 (t)exp(j2π(f 0 +nΔf)t) 0≤n≤N-1
[0042] Where u 1 (t)=rect(t / T 1 )exp(jπγt 2 ) Is the chirp sub-pulse, exp is the base of the exponential function, j is the imaginary number, f 0 Is the fundamental frequency, n is the number of FM step sub-pulses, Δf is the frequency step, f 0 +nΔf is the carrier frequency of the nth FM step sub-pulse, t is the time, N is the step FM number of the sub-pulse in each pulse group, T 1 Is the sub-pulse width, γ is the sub-pulse modulation frequency;
[0043] The distance between any scattering point P on the moving target and the radar when the radar transmits the nth sub...
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The invention relates to a step frequency inverse synthetic aperture radar (ISAR) imaging method based on coherent processing. The method mainly solves the problems in a traditional parameter estimation method of being low in calculating efficiency and having large effects of phase error on frequency synthesis after envelope compensation. The method includes the steps: building a step frequency ISAR echo signal model; conducting motion parameter estimation according to the echo signal model; constructing a penalty function and compensating a sub-pulse envelope of echo signals; conducting frequency synthesis based on coherent processing on the compensated echo signals; conducting inverse fast Fourier transformation (IFFT) on the synthesized echo signals, and obtaining a high-resolution range profile; and conducting direction imaging through an RD algorithm or an RID algorithm to obtain a directional high-resolution image. Experiments prove that the method has the advantages of being high in phase error compensation precision and calculation efficiency and can be used for achieving two-dimensional high-resolution ISAR imaging of a target.
Description
Technical field [0001] The invention belongs to the field of radar technology, and particularly relates to an inverse synthetic aperture radar high-resolution imaging technology, which can be used to achieve high-resolution two-dimensional imaging of a target. Background technique [0002] High-resolution ISAR imaging radar is widely used in modern radar systems because it can achieve two-dimensional imaging of targets and obtain richer target scattering information, which is conducive to target identification and classification. High-resolution ISAR imaging of targets needs to improve the longitudinal and lateral resolution of the radar. The lateral resolution is achieved by the rotation of the target relative to the radar, while the longitudinal resolution is achieved by the large signal bandwidth emitted by the radar. [0003] Chirp stepped signals are widely used in high-resolution imaging radar systems because they can synthesize a large signal bandwidth to improve the longit...
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IPC IPC(8): G01S13/89
Inventor 李亚超全英汇邢孟道许斌周瑞雨
Owner XIDIAN UNIV