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Xizhang Wei

Bio: Xizhang Wei is an academic researcher from National University of Defense Technology. The author has contributed to research in topics: Radar & Radar imaging. The author has an hindex of 11, co-authored 58 publications receiving 430 citations.


Papers
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Journal ArticleDOI
TL;DR: Simulation results indicate that the proposed method outperforms the existing methods in the spectrum accuracy, the range of estimable vibration amplitude/frequency, and the computation complexity.
Abstract: The intricate vibration of a working vehicle provides an important signature to the vehicle type. Small vibrations introduce phase modulation in radar echoes, which is referred to as micro-Doppler (m-D) phenomenon and can be modeled as sinusoidal frequency-modulated (SFM) signal. Such phase modulation induced by vibrations consists of multiple frequency components; moreover, the modulation is usually rather weak. Present parametric estimators are difficult to estimate so many parameters of every frequency component, while nonparametric approaches suffer from low precision. This paper considers the analysis of SFM signal with weak and multiple frequency components modulation on phase term. We first define the SFM signal space to bridge a gap between the SFM signal analysis and classical signal processing methods. Based on the defined signal space, a novel m-D analysis method, i.e., the sinusoidal frequency modulation Fourier transform (SFMFT), is presented. With the operations acting directly on the phase term of SFM signal, SFMFT gives the frequency spectrum of vibration traces. Unlike the existing methods, which apply a sliding short-time window to perform an instantaneous approximation, the proposed method makes use of the global data, which can provide a longer integral period gain, and consequently improves the estimation performance significantly. Simulation results indicate that the proposed method outperforms the existing methods in the spectrum accuracy, the range of estimable vibration amplitude/frequency, and the computation complexity.

74 citations

Journal ArticleDOI
TL;DR: In this paper, an electronic counter-countermeasure (ECCM) scheme is proposed to remove the ISRJ-based false targets from the pulse compression result of the de-chirping radar.

63 citations

Journal ArticleDOI
TL;DR: A novel framework in random PRI radar to generate the Doppler spectrum with low sidelobe for moving target detection with high performance of detection and free aliasing characteristic and can also shorten the coherent processing interval compared with traditional staggered PRI mode.
Abstract: The electronic counter-countermeasures capabilities of staggered pulse repetition interval (PRI) signal is limited by its repetitive character, and a random PRI radar is an alternative to improve the range and velocity coverage. However, the high sidelobe pedestal of the target Doppler spectrum caused by randomness prevents its development. In this paper, based on the compressed sensing theory, we present a novel framework in random PRI radar to generate the Doppler spectrum with low sidelobe for moving target detection. As a precondition, the equivalent sensing matrix is proved to satisfy the restricted isometry property by testifying its independent sub-Gaussian elements and comparing its mutual coherence as well as eigenvalues of its Gram matrices to a typical random compressed sensing matrix in a statistical sense. To cover the concerned velocity, multichannel processing is used and the iterative grid optimization algorithm is employed to eliminate the grid mismatch effect. The simulation results demonstrate that this scheme has high performance of detection and free aliasing characteristic, which can also shorten the coherent processing interval compared with traditional staggered PRI mode.

55 citations

Journal ArticleDOI
TL;DR: The authors illustrate the impact of the radar antenna geometry and target location prior density on the allocation results and demonstrate the superior performance of the proposed optimal power allocation scheme via Monte Carlo simulations.
Abstract: Power allocation in distributed multiple-input multiple-output radar is investigated for range-only target localisation such that the determinant of Bayesian Fisher information matrix (B-FIM) is maximised. The B-FIM is derived from a signal model that incorporates the propagation path loss, the target reflectivity, the transmitted power and target prior information. The authors model the problem as a cooperative game and exploit the solution concept of Shapley value to distribute a given power budget among all transmitting radars for localisation and integrate the algorithm with a sequential Bayesian estimator to localise target. In numerical simulations, it is shown that uniform power allocation is not in general optimal. They illustrate the impact of the radar antenna geometry and target location prior density on the allocation results and demonstrate the superior performance of the proposed optimal power allocation scheme via Monte Carlo simulations.

36 citations

Journal ArticleDOI
TL;DR: This letter presents a dynamic ISAR imaging algorithm based on sequential smoothed L0, which is proposed as an efficient recursive implementation of the SR approach and can seek the optimal pulse number required in each CPI.
Abstract: For maneuvering targets, the time-varying Doppler shifts will produce blurred inverse synthetic aperture radar (ISAR) images for a long coherent processing interval (CPI). By exploiting sparsity of the target scene, sparse recovery (SR) algorithms have been applied to achieve high cross-range resolution within a short CPI, during which the Doppler shifts nearly remain constant. For practical applications, however, the required pulse number for attaining an acceptable image is difficult to designate in various scenarios, and the common recovery procedure suffers from low efficiency because of having to solve a new SR problem from scratch when the new echo pulses are sequentially available. In this letter, we present a dynamic ISAR imaging algorithm based on sequential smoothed L0, which is proposed as an efficient recursive implementation of the SR approach. Furthermore, by defining the proper stopping rules, we can seek the optimal pulse number required in each CPI. Simulation results show that the proposed dynamic algorithm is more suitable for ISAR imaging of uncooperative targets.

34 citations


Cited by
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Journal ArticleDOI

[...]

08 Dec 2001-BMJ
TL;DR: There is, I think, something ethereal about i —the square root of minus one, which seems an odd beast at that time—an intruder hovering on the edge of reality.
Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

33,785 citations

Journal Article
TL;DR: The Micro-Doppler Effect in Radar by V. C. Chen as discussed by the authors is a book review of "The Micro Doppler effect in radar" by Chen et al. 2011. 290pp + diskette.
Abstract: This is a book review of 'The Micro-Doppler Effect in Radar' by V. C. Chen. Artech House, 16 Sussex Street, London, SW1V 4RW, UK. 2011. 290pp + diskette. Illustrated. £90. ISBN 978-1-60807-057-2.

439 citations

Journal ArticleDOI
TL;DR: A class of methods in TFA, parameterised TFA is focused on, summarizing its latest research progress and related engineering applications, so as to provide reference and guidance for researchers applying parametric TFA in different fields.

130 citations

Journal ArticleDOI
TL;DR: An instantaneous microwave-radar imaging technique is proposed to obtain focused high-resolution images of targets without motion limitation by shortening the imaging time to even a pulse width without resolution deterioration so as to improve the performance of processing noncooperative targets and simplifying the receiver complexity.
Abstract: Motivated by classical coincidence imaging which has been realized in optical systems, an instantaneous microwave-radar imaging technique is proposed to obtain focused high-resolution images of targets without motion limitation. Such a radar coincidence imaging method resolves target scatterers based on measuring the independent waveforms of their echoes, which is quite different from conventional radar imaging techniques where target images are derived depending on time-delay and Doppler analysis. Due to the peculiar features of coincidence imaging, there are two potential advantages of the proposed imaging method over the conventional ones: 1) shortening the imaging time to even a pulse width without resolution deterioration so as to improve the performance of processing noncooperative targets and 2) simplifying the receiver complexity, resulting in a lower cost and platform flexibility in application. The basic principle of radar coincidence imaging is to employ the time-space independent detecting signals, which are produced by a multitransmitter configuration, to make scatterers located at different positions reflect independent waveforms from each other, and then to derive the target image based on the prior knowledge of this detecting signal spatial distribution. By constructing the mathematic model, the necessary conditions of the transmitting waveforms are analyzed for achieving radar coincidence imaging. A parameterized image-reconstruction algorithm is introduced to obtain high resolution for microwave radar systems. The effectiveness of this proposed imaging method is demonstrated via a set of simulations. Furthermore, the impacts of modeling error, noise, and waveform independence on the imaging performance are discussed in the experiments.

128 citations

Journal ArticleDOI
TL;DR: The mathematic principles of ISRJ against LFM radars, which utilize matched-filter processing, stretch processing, and range-Doppler processing, are developed and the key jamming elements, which determine these false-target characteristics, are pointed out and analyzed in detail.
Abstract: Interrupted-sampling repeater jamming (ISRJ) provides a novel coherent-jamming mode against wideband radar. ISRJ allows the single-antenna jammer to periodically sample and repeat a fraction of the intercepted signal, which reduces the sampling rate and achieves transmit-receive isolation. The coherent-jamming signal generated by ISRJ can form multiple verisimilar false targets when received and processed by the victim radar receiver. Moreover, some false targets can precede the real target. This paper surveys the use of ISRJ in linear frequency modulated (LFM) radar jamming. The theory and application of ISRJ has been researched for more than one decade, but what is missing is a completed summary for the framework of this technique. In this paper, mathematic principles of ISRJ against LFM radars, which utilize matched-filter processing, stretch processing, and range-Doppler processing, are developed. The unique jamming effects in radar systems are focused on when the interrupted sampling frequency of the jammer is smaller than the bandwidth of the radar signal. Specifically, the false-target characteristics, including amplitude, space distribution, and phase, are discussed, respectively. On this basis, the key jamming elements, which determine these false-target characteristics, are pointed out and analyzed in detail. At last, simulation and real data are used to verify the correctness of the analyses. Experimental results highlight the potential application of the proposed jamming mode.

113 citations