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Xu J.,Tsinghua University | Xu J.,Radar Academy of Airforce | Dai X.-Z.,Tsinghua University | Xia X.-G.,University of Delaware | And 3 more authors.
IEEE Transactions on Aerospace and Electronic Systems | Year: 2011

This paper proposes a novel multisite radar system (MSRS) with multiple-input and multiple-output (MIMO) radars, i.e., MIMO-MSRS system, to improve the detection performance of fluctuating targets. The proposed MIMO-MSRS system increases the local signal-to-noise ratio (SNR) by using digital beamforming (DBF) among all transmitting and receiving channels in a single site. Then it smoothes the target's fluctuation via spatial diversity among the DBF outputs of different sites. For the MIMO-MSRS system, we derive the likelihood ratio test (LRT) detector at first based on the proposed signal model and spatial diversity conditions. Furthermore, with the derived statistics of the LRT detector in the fixed noise background, three optimization problems are discussed on the MIMO-MSRS system configurations, i.e., the numbers of sites and collocated channels in different sites. The first problem is to detect the lowest SNR target with a given probability of false alarm (PF), probability of detection (PD) and total system degrees of freedom (DOF). The second is to detect a target with the highest PD for a given PF, target SNR, and system DOF. The third is on the minimal system DOF to detect a target with a given PF, PD, and target SNR. For the uniform MIMO-MSRS system, both the standard optimal site number, i.e., the diversity DOF, and its closed-form approximation of the above three problems are obtained. Finally, some numerical results are also provided to demonstrate the effectiveness of the proposed MIMO-MSRS systems. © 2011 IEEE. Source


Xu J.,Tsinghua University | Xu J.,Radar Academy of Airforce | Yu J.,Tsinghua University | Peng Y.-N.,Tsinghua University | Xia X.-G.,University of Delaware
IEEE National Radar Conference - Proceedings | Year: 2010

Based on the internal coupling relationship among radial velocity, range-walk and Doppler frequency of moving target's echoes, this paper proposes a novel method, i.e., Radon-Fourier transform (RFT), to realize the long-time coherent integration for radar target detection. The RFT realizes the echoes spatial-temporal decoupling via joint searching along range and velocity directions, as well as the successive coherent integration via the Doppler filter bank. Besides, it is shown that RFT is a kind of generalized Doppler filter bank processing for targets with across range unit (ARU) range walk. Finally, numerical experiments are provided to demonstrate the effectiveness of the proposed methods. © 2010 IEEE. Source


Xu J.,Tsinghua University | Xu J.,Radar Academy of Airforce | Dai X.-Z.,Tsinghua University | Xia X.-G.,University of Delaware | And 3 more authors.
IEEE National Radar Conference - Proceedings | Year: 2010

Statistical multiple-input multiple-output (MIMO) radar may improve the fluctuated target detection by utilizing the multiple separate transmitting and receiving elements. Nevertheless, the transmitting power of single element is reciprocal to the transmitting element number, and the ultimate detection performance of MIMO radar may be inversely deteriorated with the increase of the transmitting elements. In this letter, the optimal transmitting diversity DOF, i.e., the optimal separate transmitting elements, is defined based on the proposed likelihood ratio test (LRT) detectors. Furthermore, with the given false alarm probability and detection probability, the closed-form optimal DOF approximations are derived for the two sub-forms of statistical MIMO radar, i.e., distributed MIMO radar and multiple-input single-output (MISO) radar, respectively. It is shown that a small transmitting diversity DOF, as well as the small number of orthogonal transmitting waveforms, may be needed for optimizing the statistical MIMO radar spatial diversity performance. Finally, numerical experiments are also provided to demonstrate the effectiveness of the proposed methods. © 2010 IEEE. Source


Xu J.,Beijing Institute of Technology | Xu J.,Tsinghua University | Xia X.-G.,University of Delaware | Xia X.-G.,Chonbuk National University | And 4 more authors.
IEEE Transactions on Signal Processing | Year: 2012

The slant range of a radar maneuvering target is usually modeled as a multivariate function in terms of its illumination time and multiple motion parameters. This multivariate range function includes the modulations on both the envelope and the phase of an echo of the coherent radar target and provides the foundation for radar target motion estimation. In this paper, the maximum likelihood estimators (MLE) are derived for motion estimation of a maneuvering target based on joint envelope and phase measurement, phase-only measurement and envelope-only measurement in case of high signal-to-noise ratio (SNR), respectively. It is shown that the proposed MLEs are to search the maximums of the outputs of the proposed generalized Radon-Fourier transform (GRFT), generalized Radon transform (GRT) and generalized Fourier transform (GFT), respectively. Furthermore, by approximating the slant range function by a high-order polynomial, the inherent accuracy limitations, i.e., the Cramer-Rao low bounds (CRLB), and some analysis are given for high order motion parameter estimations in different scenarios. Finally, some numerical experimental results are provided to demonstrate the effectiveness of the proposed methods. © 2012 IEEE. Source


Qian L.,Radar Academy of Airforce | Xu J.,Tsinghua University | Sun W.,Radar Academy of Airforce | Peng Y.,Tsinghua University
Proceedings of 2011 IEEE CIE International Conference on Radar, RADAR 2011 | Year: 2011

With respect to the scale effect of wideband radar echoes, this paper proposes a long-time coherent integration method, i.e., wideband scaled Radon-Fourier transform (WSRFT). It can make great improvement on the detection performance of far-range, weak and high speed target of wideband radar. The degradation of pulse compression performance caused by scale effect is studied. Range and velocity shifts of the output of standard RFT (SRFT) are analyzed. Furthermore, the detection performance comparison between WSRFT and SRFT is investigated. Finally, detailed numerical experiments are provided to demonstrate the effectiveness of the proposed WSRFT. © 2011 IEEE. Source

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