Time filter

Source Type

Zhang W.,Missile Institute | Tong C.-M.,Missile Institute | Tong C.-M.,Nanjing Southeast University | Zhang Q.,Institute of Telecommunication Engineering
Tien Tzu Hsueh Pao/Acta Electronica Sinica | Year: 2011

Aiming at extracting the time-varying micro-Doppler feature of the vibrating target in ground clutter environment, the method of micro-Doppler extraction based on dual-channel ATI technique and Radon transform is presented. The ATI technique is utilized to suppress ground clutter and obtain the interferometric signal of the vibrating target, which is presented as a straight line along the azimuth direction in the range-compressed data domain. The Radon transform is utilized to detect the weak straight line and find out which range cell it locates at. And the mathematical expressions of micro-Doppler with different vibrating directions are derived and discussed in detail. Compared with the single-channel situation, it is no need to compensate for the Doppler shift caused by the radar's translation, and the target vibrating along the azimuth direction could be effectively detected, whose micro-Doppler presents remarkably nonperiodic feature. Simulated results verify the accuracy and availability of the proposed method. Source

He J.,Institute of Telecommunication Engineering | Zhang Q.,Institute of Telecommunication Engineering | Zhang Q.,Fudan University | Yang X.-Y.,Institute of Telecommunication Engineering | And 3 more authors.
Yuhang Xuebao/Journal of Astronautics | Year: 2011

Synthetic aperture LADAR (SAL) is an active laser imaging system. It has much higher imaging resolution than the microwave synthetic aperture radar, and can realize the refined imaging for a far distance target. Due to the extra large bandwidth of laser signal, the hardware of SAL is difficult to satisfy the requirement for Nyquist sampling rate. A new signal sampling method based on the compressed sensing (CS) theory is proposed to reduce the sampling rate of echoes in this paper. In the method, the echoes are randomly sampled by using an optical heterodyne process, and then the high-resolution range profile is recovered by using the orthogonal matching pursuit algorithm (OMP). The 2-D image is recovered by using frequency scaling algorithm. Simulations demonstrate that high-quality images can be reconstructed even though the sampling rate is much lower than the Nyquist sampling rate. Source

Zhu X.-P.,Institute of Telecommunication Engineering | Zhang Q.,Institute of Telecommunication Engineering | Zhang Q.,Fudan University | Li H.-W.,Institute of Telecommunication Engineering
Yuhang Xuebao/Journal of Astronautics | Year: 2011

A method called Polar Format Algorithm(PFA) suitable for the Bistatic-ISAR system is analyzed, the coordinate transformation from polar coordinate to rectangular coordinate is achieved by linear interpolation in range dimension and non-linear interpolation in azimuth dimension. Considering the complexity in interpolation, an improved PFA is proposed by using Chirp-Z transformation to replace the range dimension interpolation, thus reducing computational complexity greatly and obtaining the same effect as interpolation. Simulations of scatter points have demonstrated the validity of the proposed improved algorithm. Source

Zhu R.-F.,Institute of Telecommunication Engineering | Zhu X.-P.,Institute of Telecommunication Engineering | Zhang Q.,Institute of Telecommunication Engineering | Zhang Q.,Fudan University
Yuhang Xuebao/Journal of Astronautics | Year: 2012

A method is proposed for solving the problem when using Frequency Modulation Continuous Wave(FMCW) in Bi-static ISAR system. Considering coupling terms induced by using FMCW signal, the Discrete Polynomial Phase Transform(DPT) is used to estimate the combined component, then the phases of echo signal are compensated by using compensation functions to eliminate the fixed frequency offset caused by first coupling term and main-lobe expansion induced by second coupling term. The Range Doppler algorithm is used to attain clear target's image. At last, the validity of the proposed compensation algorithm is validated by simulation and focused image is obtained. Source

Deng D.H.,Institute of Telecommunication Engineering | He J.,Institute of Telecommunication Engineering | Wang M.,Institute of Telecommunication Engineering | Zhang Q.,Institute of Telecommunication Engineering | Bai P.,AFEU
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

If the target or any structure on the target undergoes micro-motion dynamics, such as mechanical vibrations or rotations, it will induce Doppler frequency modulation on the returned signal that generates sidebands about the target's Doppler frequency, which is referred to as the micro-Doppler effect. The micro-Doppler signatures enable certain properties of the target to be determined that may be used for target recognition. In this paper, taking the Micro-Doppler effect caused by the rotation of target in Bi-static inverse synthetic aperture radar (Bi-ISAR) system as example, a novel extraction method of the micro-motion feature is presented. With the proposed method, the micro-motion parameters of the target can be detected rapidly from the spectrogram and the computational efficiency can be enhanced compared with that of the modified extended Hough transform. A computer simulation is given to illustrate the effectiveness of the proposed method. © 2011 IEEE. Source

Discover hidden collaborations