摘要 :
The general approach to ISAR imaging is range-Doppler (RD) imaging approach. For this approach, the translational motion compensation (TMC) is firstly obtained by envelope alignment and autofocus, so the target can be treated as a...
展开
The general approach to ISAR imaging is range-Doppler (RD) imaging approach. For this approach, the translational motion compensation (TMC) is firstly obtained by envelope alignment and autofocus, so the target can be treated as a rotating target for the next processing. But in this method, scatterers' migration through resolution cells (MTRC) caused by rotational motion is neglected. However in practice, MTRC exists with the improvement of resolution or for big target. For MTRC compensation, a keystone transformation in SAR is used in this paper. Before keystone transformation, it is demanded that the raw data is coherent, while in fact, the ISAR raw data is usually not. So a coherent processing of raw data is proposed. In this paper, the coherent processing of raw data is firstly done and the next step is to correct MTRC. Finally a parameter estimation method of multi-component amplitude modulation and linear frequency modulation (AM-LFM) signal is proposed to estimate the scatterers' instantaneous amplitudes and frequencies, and the range-Instantaneous Doppler (RID) ISAR image is obtained. The effective of this algorithm is testified by the processing of simulation data.
收起
摘要 :
The general approach to ISAR imaging is range-Doppler (RD) imaging approach. For this approach, the translational motion compensation (TMC) is firstly obtained by envelope alignment and autofocus, so the target can be treated as a...
展开
The general approach to ISAR imaging is range-Doppler (RD) imaging approach. For this approach, the translational motion compensation (TMC) is firstly obtained by envelope alignment and autofocus, so the target can be treated as a rotating target for the next processing. But in this method, scatterers' migration through resolution cells (MTRC) caused by rotational motion is neglected. However in practice, MTRC exists with the improvement of resolution or for big target. For MTRC compensation, a keystone transformation in SAR is used in this paper. Before keystone transformation, it is demanded that the raw data is coherent, while in fact, the ISAR raw data is usually not. So a coherent processing of raw data is proposed. In this paper, the coherent processing of raw data is firstly done and the next step is to correct MTRC. Finally a parameter estimation method of multi-component amplitude modulation and linear frequency modulation (AM-LFM) signal is proposed to estimate the scatterers' instantaneous amplitudes and frequencies, and the Range-Instantaneous Doppler (RID) ISAR image is obtained. The effective of this algorithm is testified by the processing of simulation data.
收起
摘要 :
The general approach to ISAR imaging is range-Doppler (RD) imaging approach. For this approach, the translational motion compensation (TMC) is firstly obtained by envelope alignment and autofocus, so the target can be treated as a...
展开
The general approach to ISAR imaging is range-Doppler (RD) imaging approach. For this approach, the translational motion compensation (TMC) is firstly obtained by envelope alignment and autofocus, so the target can be treated as a rotating target for the next processing. But in this method, scatterers' migration through resolution cells (MTRC) caused by rotational motion is neglected. However in practice, MTRC exists with the improvement of resolution or for big target. For MTRC compensation, a keystone transformation in SAR is used in this paper. Before keystone transformation, it is demanded that the raw data is coherent, while in fact, the ISAR raw data is usually not. So a coherent processing of raw data is proposed. In this paper, the coherent processing of raw data is firstly done and the next step is to correct MTRC. Finally a parameter estimation method of multi-component amplitude modulation and linear frequency modulation (AM-LFM) signal is proposed to estimate the scatterers' instantaneous amplitudes and frequencies, and the range-Instantaneous Doppler (RID) ISAR image is obtained. The effective of this algorithm is testified by the processing of simulation data.
收起
摘要 :
The anntenna area of distributed micosateliites radar system is usually smaller than the minimum SAR antenna area constraint, and there are range-Doppler ambiguities. So one key focus of this signal processing research is to devel...
展开
The anntenna area of distributed micosateliites radar system is usually smaller than the minimum SAR antenna area constraint, and there are range-Doppler ambiguities. So one key focus of this signal processing research is to develop processing approaches that exploit the added degrees of freedom of a spatially diverse formation to resolve inherent ambiguities of this sparse aperture distributed micosateliites radar system. In the paper, a beamform processing method of three-dimensional sparse arrays is proposed to spatially null Doppler ambiguities. This method first filters out each unambiguous frequency point from ambiguous Doppler channels of a few different phase centers by using spatial filter, this processing can be regard as a space-time processing, then combines all unambiguous frequency point to a whole unambiguous Doppler band, after that, does imaging processing. Theoretical derivation, performance analysis, and simulation of this method are discussed in the paper.
收起
摘要 :
The anntenna area of distributed micosateliites radar system is usually smaller than the minimum SAR antenna area constraint, and there are range-Doppler ambiguities. So one key focus of this signal processing research is to devel...
展开
The anntenna area of distributed micosateliites radar system is usually smaller than the minimum SAR antenna area constraint, and there are range-Doppler ambiguities. So one key focus of this signal processing research is to develop processing approaches that exploit the added degrees of freedom of a spatially diverse formation to resolve inherent ambiguities of this sparse aperture distributed micosateliites radar system. In the paper, a beamform processing method of three-dimensional sparse arrays is proposed to spatially null Doppler ambiguities. This method first filters out each unambiguous frequency point from ambiguous Doppler channels of a few different phase centers by using spatial filter, this processing can be regard as a space-time processing, then combines all unambiguous frequency point to a whole unambiguous Doppler band, after that, does imaging processing. Theoretical derivation, performance analysis, and simulation of this method are discussed in the paper.
收起
摘要 :
The anntenna area of distributed micosateliites radar system is usually smaller than the minimum SAR antenna area constraint, and there are range-Doppler ambiguities. So one key focus of this signal processing research is to devel...
展开
The anntenna area of distributed micosateliites radar system is usually smaller than the minimum SAR antenna area constraint, and there are range-Doppler ambiguities. So one key focus of this signal processing research is to develop processing approaches that exploit the added degrees of freedom of a spatially diverse formation to resolve inherent ambiguities of this sparse aperture distributed micosateliites radar system. This paper proposed a Doppler ambiguity resolving method which makes the Doppler ambiguities null in Doppler domain using spatial filter of multiple phase centres.
收起
摘要 :
Usually inverse synthetic aperture radar (ISAR) imaging is for small aircraft, with long range, moreover the coherent integration angle is small, that is the target's wavenumber spectrum support region can be regard as a rectangle...
展开
Usually inverse synthetic aperture radar (ISAR) imaging is for small aircraft, with long range, moreover the coherent integration angle is small, that is the target's wavenumber spectrum support region can be regard as a rectangle, Range-Doppler(RD) algorithm or Range-Instantaneous-Doppler (RID) algorithm are employed for image reconstruction after translational motion compensation (TMC), which includes envelope alignment (such as envelope correlation algorithm, minimum entropy algorithm) and autofocus (such as single PPP algorithm, multiple PPP algorithm, PGA, weighted least square algorithm). But migration through resolution cell (MTRC) is not considered after TMC, in fact, the scatterers around the target usually take place MTRC if the size of target is large. In the paper, we first align and focus the high resolution radar target echoes according target center, then we do time scale transform in target's wavenumber domain, that is Soumekh proposed 'keystone' interpolation to compensate MTRC (which can also be realized rapidly by DFT-IFFT or SFT-IFFT in azimuth direction), after range compression (range IFFT), for steadily flying target, target image can be obtained only after azimuth compression (that is FFT in azimuth direction), for maneuvering target, time-frequency analysis must be taken for every range cell, and the existing instantaneous imaging algorithms (such as joint time-frequency distribution algorithm, Radon-Wigner algorithm) are also effective to obtain RID images. This paper gives the ISAR imaging algorithm flow diagram to obtain images from raw data of steadily flying and maneuvering big targets, and simulate data and real data prove that algorithm flow is effective.
收起
摘要 :
One dimensional (1D) images can be used to characterize the major features of the target and serve for the purpose of automatic target recognition (ATR). For conventional low resolution radar, 1D range profiles cannot be measured,...
展开
One dimensional (1D) images can be used to characterize the major features of the target and serve for the purpose of automatic target recognition (ATR). For conventional low resolution radar, 1D range profiles cannot be measured, but 1D cross-range images can be obtained by processing a sequence of radar echoes. There have been few papers in the literature discussing how to obtain 1D cross-range images, but the image resolutions obtained are low, and even some wrong images were obtained because of the following two reasons: one is that translational motion compensation (TMC) is not correct; the other is that 3D and nonuniform rotational motions are not considered. In this paper we propose new methods to tackle these two problems. First we use the minimum entropy method to compensate the translational motion. Second, based on the observation that the scatterer sub-echoes are not sinusoidal and should be approximated as linear frequency modulation (LFM) signals after TMC due to the 3D and nonuniform rotation of the target, we propose an extended RELAX high resolution method to estimate the multicomponent LFM signals, and obtain dynamic instantaneous 1D cross-range images. The methods are evaluated using both simulated data and real radar data.
收起
摘要 :
One dimensional (1D) images can be used to characterize the major features of the target and serve for the purpose of automatic target recognition (ATR). For conventional low resolution radar, 1D range profiles cannot be measured,...
展开
One dimensional (1D) images can be used to characterize the major features of the target and serve for the purpose of automatic target recognition (ATR). For conventional low resolution radar, 1D range profiles cannot be measured, but 1D cross-range images can be obtained by processing a sequence of radar echoes. There have been few papers in the literature discussing how to obtain 1D cross-range images, but the image resolutions obtained are low, and even some wrong images were obtained because of the following two reasons: one is that translational motion compensation (TMC) is not correct; the other is that 3D and nonuniform rotational motions are not considered. In this paper we propose new methods to tackle these two problems. First we use the minimum entropy method to compensate the translational motion. Second, based on the observation that the scatterer sub-echoes are not sinusoidal and should be approximated as linear frequency modulation (LFM) signals after TMC due to the 3D and nonuniform rotation of the target, we propose an extended RELAX high resolution method to estimate the multicomponent LFM signals, and obtain dynamic instantaneous 1D cross-range images. The methods are evaluated using both simulated data and real radar data.
收起
摘要 :
High-frequency(HF) skywave over-the-horizon
radar(OTHR) looks down its targets from the ionosphere, it
has a large operating range and a large cover areas, but it
received a large-amplitude backscatterer echo form the
terrain...
展开
High-frequency(HF) skywave over-the-horizon
radar(OTHR) looks down its targets from the ionosphere, it
has a large operating range and a large cover areas, but it
received a large-amplitude backscatterer echo form the
terrain and sea, and strong interference, such as, radio
frequency interference, industrial interference, impulsive
noise, lightning impulsive, meteor trail echoes and so on.
Interference can be divided into long time interference and
transient interference, transient interference lasts a short
time, but its intensity is great. This paper first discusses the
character of transient interference, and uses eigen-
decomposition to separate the sea clutter subspace and
filter it, or filters terrestrial clutter in frequency domain and
back to time domain, then the transient interference is
detected, after that the transient interference are excised
from the original echoes, finally, the excised clutter and
target echoes are predicted by Burg linear prediction
algorithm. This processing method has been successfully
applied to the real data from China experimental OTHR.
收起
原文获取