In order to improve the inverse synthetic aperture radar (ISAR) imaging quality of precession space target, an algorithm based on phase matching processing (PMP) of complex range profile envelope (CRPE) is proposed in this paper. By phase matching processing, only the echo components located at the scattering points corresponding to the main body of the warhead can be coherently accumulated. The echoes of other scattering centers without any coherence will cancel each other when they are transformed. Hence, the focusing of scatters centers of the warhead main body is improved and the interference caused by non-spin symmetric components is well suppressed. Simulation results confirmed the effectiveness of the method.
An inverse synthetic aperture radar (ISAR) high-precision compensation method is proposed based on coherent processing of intermediate frequency direct sampling data. First, the compensation of high-speed movement is performed by a modified linear frequency modulation matched filter during the pulse compression. The motion trajectory in the down-range direction is then reconstructed by compensation of window sampling difference of each pulse. Modified envelope correlation is applied to calculate the range profile shift between each pulse and the first one. Polynomial fitting is adopted to accurately estimate the motion characteristics. Subsequently, coherent processing is applied by combining range alignment and initial phase compensation. The migration through range cells correction can be then realized by keystone transform to the highly coherent data. Consequently, ISAR images with high quality are achieved. Experimental results on simulated and real data have demonstrated the validity of the proposed method.
Data fusion using subbands, which can obtain a higher range resolution without altering the bandwidth, hardware, and sampling rate of the radar system, has attracted more and more attention in recent years. A method of ISAR imaging based on subbands fusion and high precision parameter estimation of geometrical theory of diffraction (GTD) model is presented in this paper. To resolve the incoherence problem in subbands data, a coherent processing method is adopted. Based on an all-pole model, the phase difference of pole and scattering coefficient between each sub-band is used to effectively estimate the incoherent components. After coherent processing, the high and low frequency sub-band data can be expressed as a uniform all-pole model. The gapped-data amplitude and phase estimation (GAPES) algorithm is used to fill up the gapped band. Finally, fusion data is gained by high precision parameter estimation of GTD-all-pole model with full-band data, such as scattering center number, scattering center type and amplitude. The experimental results of simulated data show the validity of the algorithm.
The radar targets number increases from one to more when the ballistic missile is in the process of separating the lower stage rocket or casting covers or other components. It is vital to identify the warhead target quickly among these multiple targets for radar tracking. A fast recognition method of the warhead target is proposed to solve this problem by using kinematic features, utilizing fuzzy comprehensive method and information fusion method. In order to weaken the influence of radar measurement noise, an extended Kalman filter with constant jerk model (CJEKF) is applied to obtain more accurate target’s motion information. The simulation shows the validity of the algorithm and the effects of the radar measurement precision upon the algorithm’s performance.
We propose a new image registration method based on joint respective window sampling (RWS) and modified motion compensation (MMC) in an interferometric inverse synthetic aperture radar (InISAR) imaging system using two antennas. The causation and quantitative analysis of the offset between two ISAR images of different antennas along the baseline are analyzed. In the proposed method, the RWS method, according to the measured distance between the target and different antennas, compensates the offset in the range direction. The MMC method is adopted to eliminate the offset in the Doppler direction. Simulation results demonstrate that the offset between the two ISAR images can be compensated effectively, consequently achieving a high-quality three-dimensional InISAR image.
This paper proposes a new image registration method based on grade-by-grade matching in interferometric inverse
synthetic aperture radar (InISAR) imaging system using two antennas. The causation and quantitative analysis of the
offset between two ISAR images for different antennas along each baseline is analyzed. Strong scatterer centers (SSCs)
are extracted from the ISAR images of each antenna by OTSU method firstly. A standard matching is calculated by the
image centroid. Then a mapping of region of interest (ROI) and correlation is carried out to get the precise registration.
Simulation results demonstrate that the offset between two ISAR images can be compensated effectively when the
proposed method is used, achieving a high quality 3D InISAR image consequently.
In this paper the effects of orbits motion makes for scattering centers trajectory is analyzed, and introduced to scattering
centers association, as a constraint. A screening method of feature points is presented to analysis the false points of
reconstructed result, and the wrong association which lead these false points. The loop iteration between 3D
reconstruction and association result makes the precision of final reconstructed result have a further improvement. The
simulation data shows the validity of the algorithm.
Interferometric inverse synthetic aperture radar (InISAR) imaging provides complementary information to monostatic inverse synthetic aperture radar (ISAR) imaging. This paper proposes a new InISAR imaging system for space targets based on wideband direct sampling using two antennas. The system is easy to realize in engineering since the motion trajectory of space targets can be known in advance, which is simpler than that of three receivers. In the preprocessing step, high speed movement compensation is carried out by designing an adaptive matched filter containing speed that is obtained from the narrow band information. Then, the coherent processing and keystone transform for ISAR imaging are adopted to reserve the phase history of each antenna. Through appropriate collocation of the system, image registration and phase unwrapping can be avoided. Considering the situation not to be satisfied, the influence of baseline variance is analyzed and compensation method is adopted. The corresponding size can be achieved by interferometric processing of the two complex ISAR images. Experimental results prove the validity of the analysis and the three-dimensional imaging algorithm.
ISAR (inverse synthetic aperture radar) can generate 2D image of a non-cooperative moving target and be used for military and civilian purpose. For moving target,well-focused ISAR images can be achieved using appropriate motion compensation and image reconstruction algorithm. The ISAR image will be difficultly when the echo is at a low signal-to-noise level. For polarimetric ISAR system which transmits and receives different polarisation signal in both two channels, the fusion of HRRP (high range resolution profile) from different channels will improve significantly the SNR of the signal. The method proposed in this paper firstly fuses the different channels HRRP to get a higher SNR signal. Then the target region is extracted in fused HRRP. Finally, the motion compensation for ISAR imaging is carried out only on the extracted target region data in the sense of using image reconstruction method to gain a focused ISAR image. The real measured data shows the validity of the algorithm.
High speed movement of target leads to quadratic phase of the dechirped signal. A new high speed movement compensation method based on integrated cubic phase function is proposed. Numerical result shows that the algorithm can precisely estimate the quadratic phase coefficient and compensate the high resolution range profile under low signal to noise ratio. After compensation, the aberration of range profile is revised and the quality of ISAR image is greatly improved. In this way, the effectiveness of the method is verified.
An underwater metal pipeline detector is designed based on the principle of artificial source electromagnetic detection, which is used for detecting the deeply buried in underwater metal pipes. Narrowband band-pass filter in the receiver can well separate the specific frequency signal from mixed signal which is containing strong noise. Authors deduced the narrowband filter transfer function and simulated in computer, and the detector was applied in instrument prototype. Experiment results show that the error of the center frequency of the band-pass filter is small, and the gain is stable. In conclusion the detector has good performance.
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