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Direction-of-arrival estimation for uniform circular arrays under small sample size

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Journal of Systems Engineering and Electronics 2016年第6期27卷 1142-1150页

作者： Guojun Jiang Xingpeng Mao Yongtan Liu School of Electronics and information Engineering Harbin Institute of Technology collaborative innovation center of information sensing and understanding Harbin Institute of Technology

With a small number of snapshots, performances of uniform circular array (UCA) root-MUSIC based methods for directionof- arrival (DOA) estimation suffer serious degradation, because the beamspace sample covariance matrix (BSCM) severely deviates from the true one. To solve this problem, an iterative technique is proposed. The proposed technique has two key points: transform array data into beamspace data and construct a BSCM; modify the BSCM repeatedly by removing the residual parts. Meanwhile, error and beamspace leakage associated with the BSCM are investigated. The proposed technique can significantly reduce the error and the beamspace leakage which in turn could improve the performance for DOA estimation. Simulation results are given to illustrate the superiority of the proposed technique for uncorrelated and correlated signals. © 2016 Beijing Institute of Aerospace information.

关键词： Covariance matrix Error analysis Errors Iterative methods Matrix algebra

Low-Profile Dual-Polarized Planar Antenna with Compact Structure for Base Stations

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Chinese Journal of Electronics 2017年第5期26卷 1092-1095页

作者： LIU Ying WANG Jiu GONG Shuxi Science and Technology on Antenna and Microwave Laboratory Collaborative Innovation Center of Information Sensing and UnderstandingXidian University

A low-profile dual-polarized planar antenna with compact structure for 2.4GHz Wireless local area network(WLAN) and 2.5GHz Long term evaluation(LTE2500) base stations is proposed.A combination of a planar radiator and compact Artificial magnetic conductor(AMC) reflector is utilized to achieve a full planar structure without adding extra matching circuit,an extremely low-profile of 0.127 wavelength,as well as a high front to back ratio(F/B) of 25 *** antenna is fabricated to test the performance such as S-parameters,radiation patterns and peak *** results show the suitability of the proposed antenna for 2.4GHz WLAN and LTE2500 applications.

关键词： Low profile Planar Compact structure Base station antenna

Numerical Evaluation of Effect of Motion of Samples on Ptychographic Imaging and Solution with a Random Phase Modulator

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Chinese Physics Letters 2016年第2期33卷 43-46页

作者：李昭慧张建奇刘德连王晓蕊 School of Physics and Optoelectronic Engineering Xidian University collaborative innovation center of information sensing and understanding Xidian University

The retrieval of ptychographical imaging encounters a degradation produced by motion of samples. The mech- anism of capturing the diffractive patterns of a sample which is motile is simulated numerically. The relation between the retrieval degradation and the amplitude of motion is evaluated quantitatively. Experiments indicate that the reliability and resolution of the complex amplitude retrieval of a sample is inversely proportional to its vibratory amplitude. A random phase modulated aperture is employed to cure the degradation produced by the motion of samples to a certain extent.

关键词： of et is with PIE RPM into that MSE on CCD

Full aperture imaging algorithm for highly squinted TOPS SAR

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Journal of Systems Engineering and Electronics 2016年第6期27卷 1168-1175页

作者： Sheng Zhang Guangcai Sun Mengdao Xing National Laboratory of Radar Signal Processing Xidian University collaborative innovation center of information sensing and understanding Xidian University

Aiming at solving the azimuth signal aliasing problem in the Doppler domain, the azimuth time aliasing problem after range cell migration correction (RCMC) and the severe range and the azimuth coupling problem in both the phase and envelope for highly squinted terrain observation by progressive scans (TOPS) synthetic aperture radar (SAR), a novel full aperture imaging algorithm is presented. An unaliased two-dimensional (2-D) spectrum is first obtained by the azimuth preprocessing; the modified range migration algorithm (RMA) is then used to complete RCMC; and finally the azimuth signal is focused in the Doppler domain by spectral analysis (SPECAN) and deramping. Simulations and real data processing results validate the effectiveness of the proposed algorithm. © 2016 Beijing Institute of Aerospace information.

关键词： Data handling Radar Radar imaging Spectrum analysis

How to Select the Best Sensors for TDOA and TDOA/AOA Localization?

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China Communications 2019年第2期16卷 134-145页

作者： Yue Zhao Zan Li Benjian Hao Pengwu Wan Linlin Wang State Key Laboratory of Integrated Service Networks Xidian University collaborative innovation center of information sensing and understanding

This paper focuses on the sensor subset optimization problem in time difference of arrival(TDOA) passive localization scenario. We seek for the best sensor combination by formulating a non-convex optimization problem, which is to minimize the trace of covariance matrix of localization error under the condition that the number of selected sensors is given. The accuracy metric is described by the localization error covariance matrix of classical closed-form solution, which is introduced to convert the TDOA nonlinear equations into pseudo linear equations. The non-convex optimization problem is relaxed to a standard semi-definite program(SDP) and efficiently solved in a short time. In addition, we extend the sensor selection method to a mixed TDOA and angle of arrival(AOA) localization scenario with the presence of sensor position errors. Simulation results validate that the performance of the proposed sensor selection method is very close to the exhaustive search method.

关键词： sensor selection localization TDOA/AOA non-convex convex relaxation

Wideband MIMO Radar Waveform Optimization Based on Range Profile

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Journal of Beijing Institute of Technology 2019年第1期28卷 137-145页

作者： Qun Zhang Yishuai Gong Yijun Chen Institute of information and Navigation Air Force Engineering University collaborative innovation center of information sensing and understanding

Aiming at the signal bandwidth design problem for multi-target imaging task,a kind of multiple input multiple output(MIMO)radar waveform design method is *** first,the closed-loop feedback between the range profile and the signal bandwidth,which can design the minimum bandwidth of a transmitting signal that can distinguish each scatterer of the target in range direction,is ***,considering the request of beam pattern and the bandwidth limitation,a waveform optimization model is established and ***,the multi-target observation and the dynamic adjustment of the signal bandwidth are *** the end,the simulation results prove the performance of the algorithm in a low SNR circumstance.

关键词： multiple input multiple output(MIMO)radar cognition waveform design range profile range resolution

Fractional Frequency Offset Estimation for OFDM Systems in Non-Cooperative Communication

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China Communications 2016年第9期13卷 65-71页

作者： Mingqian Liu Jian Chen Bingbing Li Junfang Li State Key Laboratory of Integrated Service Networks Xidian University collaborative innovation center of information sensing and understanding Xidian University

The traditional fractional frequency offset(FFO) estimation schemes for orthogonal frequency division multiplexing(OFDM) in non-cooperative communication have the problems of susceptible performance with the frequency offset values and the number of OFDM symbols,a novel fractional frequency offset blind estimation scheme based on EKF for OFDM systems is *** nonlinear function of the frequency offset is calculated by employing the *** then the frequency offset is estimated by means of the iterative algorithm of *** finally fractional frequency offset is estimated by adopting repeated the above *** results demonstrate that the proposed scheme is robust to the frequency offset values without any requirements of a prior knowledge.

关键词： parameter estimation fractional frequency offset orthogonal frequency division multiplexing extended kalman filter

Hybrid beamforming with discrete phase shifters for millimeter wave backhaul networks

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The Journal of China Universities of Posts and Telecommunications 2018年第5期25卷 31-38页

作者： Yuan Jiangwei Li Xiaohui Pu Wenjuan Yang Xu State Key Laboratory of Integrated Service Networks Xidian University collaborative innovation center of information sensing and understanding Xidian University

Hybrid beamforming（ HBF） technology becomes one of the key technologies in the millimeter wave（ mm Wave）mobile backhaul systems,for its lower complexity and low power consumption compared to full digital beamforming（ DBF）. Two structures of HBF exist in the mm Wave mobile backhaul system,namely,the fully connected structures（ FCS） and partially connected structures（ PCS）. However,the existing methods cannot be applied to both structures. Moreover,the ideal phase shifter is considered in some current HBF methods,which is not realistic. In this paper,a HBF algorithm for both structures based on the discrete phase shifters is proposed in the mm Wave mobile backhaul systems. By using the principle of alternating minimization,the optimization problem of HBF is decomposed into a DBF optimization problem and an analog beamforming（ ABF） optimization *** the least square（ LS） method is enabled to solve the optimization model of DBF. In addition,the achievable data rate for both structures with closed-form expression which can be used to convert the optimization model into a single-stream beamforming optimization model with per antenna power constraint is derived. Therefore,the ABF is easily solved. Simulation results show that the performance of the proposed HBF method can approach the full DBF by using a lower resolution phase shifter.

关键词： millimeter wave backhanl networks fully connected structure partially connected structure hybrid beamforming limited phase shiftersresolution

Improved Q-learning algorithm for load balance in millimeter wave backhaul networks

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The Journal of China Universities of Posts and Telecommunications 2018年第3期25卷 8-16页

作者： Meng Danfeng Li Xiaohui Pu Wenjuan State Key Laboratory of Integrated Service Networks Xidian University collaborative innovation center of information sensing and understanding Xidian University

With the intensive deployment of users and the drastic increase of traffic load, a millimeter wave （mmWave） backhaul network was widely investigated. A typical mmWave backhaul network consists of the macro base station （MBS） and the small base stations （SBSs）. How to efficiently associate users with the MBS and the SBSs for load balancing is a key issue in the network. By adding a virtual power bias to the SBSs, more users can access to the SBSs to share the load of the MBS. The bias values shall be set reasonably to guarantee the backhaul efficiency and the quality of service （QoS）. An improved Q-learning algorithm is proposed to effectively adjust the bias value for each SBS. In the proposed algorithm, each SBS becomes an agent with independent learning and can achieve the best behavior, namely the optimal bias value through a series of training. Besides, an improved behavior selection mechanism is adopted to improve the learning efficiency and accelerate the convergence of the algorithm. Finally, simulations conducted in the 60 GHz band demonstrate the superior performance of the proposed algorithm in backhaul efficiency and user outage probability.

关键词： millimeter wave backhaul networks load balance user association Q-learning