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On the MIMO channel capacity saturation for spatially constrained receive region

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Journal of Systems Engineering and Electronics 2007年第3期18卷 437-442页

作者： Wu Yujiang nie zaiping School of Electronic Engineering Univ. of Electronic Science and Technology Chengdu 610054 P. R. China

In MIMO wireless communication systems, when more and more antennas are packed into spatiallylimited receive region, the antenna saturation phenomenon will appear. Moreover, the electromagnetic interactions among antennas will also become stronger and stronger and affect the antenna saturation effect considerably. Despite this, few studies consider these two effects jointly. The effects of antenna saturation are investigated under the consideration of mutual coupling, thus a more practical and physically meaningful result can be obtained.

关键词： MIMO systems capacity saturation mutual coupling spatially constrained array.

On the improvement of the mutual coupling compensation in DOA estimation

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Journal of Systems Engineering and Electronics 2008年第1期19卷 1-6页

作者： Wu Yujiang nie zaiping Univ. of Electronic Science and Technology Chengdu 610054 P. R. China Tongyu Comm. Equipment Co. Ltd. Zhangshan 528437 P.R.China

A new and exact calculation method for the mutual impedance matrix of receiving arrays is proposed. The mutual impedance matrix is derived from electromagnetic boundary conditions and can be used to relate the coupling free open-circuit voltages, instead of the conventional ones, to the measured voltages. A remarkable improvement on compensation for the coupling effects is shown in the direction finding applications, while a simple relationship between measured terminal voltages and the coupling free voltages is remained.

关键词： mutual coupling reaction concept mutual impedance receiving array

Low spatial correlation at base station uniform linear antennas

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Journal of Systems Engineering and Electronics 2006年第4期17卷 709-711页

作者： Xiao Hailin nie zaiping School of Electronic Engineering Univ. of Electronic Science and Technology Chengdu 610054 E R. China

A spatial channel propagation model is presented. Consider a uniform linear antenna （ULA） at the base station （BS） and narrowband signals transmitted at the mobile. In two types of propagating environments： indoor and outdoor, performance of low spatial correlation is investigated and some results are provided, which are significant to an,3. lyze the performance of diversity systems and configuration of army. The results also show that the configuration of array with either smaller angular spread or bigger angle of arrival （AOA） dominates the impact on spatial correlation, and that increasing angular spread or decreasing AOA diminishes, or even eliminates this impact.

关键词： spatial correlation uniform linear antennas angular spread angle of arrival.

Efficient analysis of dielectric radomes using multilevel fast multipole algorithm with CRWG basis

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Journal of Systems Engineering and Electronics 2008年第1期19卷 81-87页

作者： Que Xiaofeng nie zaiping Hu Jun School of Electronic Engineering Univ. of Electronic Science and Technology of China Chengdu 610054 P. R. China

A full-wave analysis of the electromagnetic problem of a three-dimensional （3-D） antenna radiating through a 3-D dielectric radome is preserued. The problem is formulated using the Poggio-Miller-Chang-Harrington- Wu（PMCHW） approach for homogeneous dielectric objects and the electric field integral equation for conducting objects. The integral equations are discretized by the method of moment （MoM）, in which the conducting and dielectric surface/interfaces are represented by curvilinear triangular patches and the unknown equivalent electric and magnetic currents are expanded using curvilinear RWG basis functions. The resultant matrix equation is then solved by the multilevel fast multipole algorithm （MLFMA） and fast far-field approximation （FAFFA） is used to further accelerate the computation. The radiation patterns of dipole arrays in the presence of radomes are presented. The numerical results demonstrate the accuracy and versatility of this method.

关键词： multilevel fast multipole algorithm antenna radome curvilinear RWG basis PMCHW formulation fast far-field approximation.

Co-aperture arrangement of dual antennas for orientation and telemetry in a conformal cavity

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Journal of Systems Engineering and Electronics 2008年第6期19卷 1133-1138页

作者： Zong Xianzheng nie zaiping Wang Jun School of Electronic Engineering Univ. of Electronic Science and Technology Chengdu 610054 P. R. China Inst. of Electronic Engineering Chinese Academy of Engineering Physics Mianyang 621900 P. R. China

The feasibility of making two antennas work within a shared aperture conformai to a platform like an aircraft or a missile is investigated. The shared aperture is enclosed by a deep cavity, which is covered by a columniform dielectric radome. A modified quadrifilar helix antenna （QHA） with extended volute arms and a vertical monopole with a ring shaped ground are arranged in this co-aperture for global position system （GPS） orientation and telemetry, respectively. The effects of the cavity on these two antennas and the mutual coupling between these two antennas are studied through large numbers of experiments. The results show that the QHA has a strong influence on the monopole; however, these two antennas of the overall arrangement can perform simultaneously well within the aperture. The QHA has a right hand circular polarization （RHCP） and a broad beam normal to the radome topside, meanwhile the monopole can be used to produce a main lobe in the grazing direction above the aperture in some certain cases of the vertical location of the QHA in the cavity.

关键词： antennas co-aperture cavity radome

Fast and accurate analysis of electromagnetic scattering from targets situated in dielectric half space

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Journal of Systems Engineering and Electronics 2010年第1期21卷 37-40页

作者： Yongpin Chen zaiping nie Jun Hu School of Electronic Engineering University of Electronics Science and Technology of China Chengdu 610054 E R. China

Electromagnetic scattering from targets situated in half space is solved by applying fast inhomogeneous plane wave algorithm combined with a tabulation and interpolation method. The integral equation is set up based on derivation of dyadic Green＇s functions in this environment. The coupling is divided into nearby region and well-separated region by grouping. The Green＇s function can be divided into two parts： primary term and reflected term. In the well-separated region, the two terms are both expressed as Sommerfeld integral, which can be accelerated by deforming integral path and taking interpolation and extrapolation. For the nearby region, the direct Sommerfeld integral makes the filling of impedance matrix time-expensive. A tabulation and interpolation method is applied to speed up this process. This infinite integral is pre-computed in sampling region, and a two-dimensional table is then set up. The impedance elements can then be obtained by interpolation. Numerical results demonstrate the accuracy and efficiency of this algorithm.

关键词： electromagnetic scattering dielectric half space fast inhomogeneous plane wave algorithm tabulation and interpolation.

Channel capacity and digital modulation schemes in correlated Weibull fading channels with nonidentical statistics

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Journal of Systems Engineering and Electronics 2007年第2期18卷 205-209页

作者： Xiao Hailin nie zaiping Yang Shiwen School of Electronic Engineering Univ. of Electronic Science and Technology of Chinas Chengdu 610054 P. R. China

The novel closed-form expressions for the average channel capacity of dual selection diversity is presented, as well as, the bit-error rate （BER） of several coherent and noncoherent digital modulation schemes in the correlated Weibull fading channels with nonidentical statisticS. The results are expressed in terms of Meijer＇s Gfunction, which can be easily evaluated numerically. The simulation results are presented to validate the proposed theoretical analysis and to examine the effects of the fading severity on the concerned quantities.

关键词： Average channel capacity Weibull fading channels Bit-error rate Digital modulation Nonidentical statistics.

Fast computation of scattering from 3D complex structures by MLFMA

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Journal of Systems Engineering and Electronics 2008年第5期19卷 872-877页

作者： Hu Jun nie zaiping Que Xiaofeng Meng Min Coll. of Electronic Engineering Univ. of Electronic Science and Technology of China Chengdu 610054 P. R. China

This paper introduces the research work on the extension of multilevel fast multipole algorithm （MLFMA） to 3D complex structures including coating object, thin dielectric sheet, composite dielectric and conductor, cavity. The impedance boundary condition is used for scattering from the object coated by thin lossy material. Instead of volume integral equation, surface integral equation is applied in case of thin dielectric sheet through resistive sheet boundary condition. To realize the fast computation of scattering from composite homogeneous dielectric and conductor, the surface integral equation based on equivalence principle is used. Compared with the traditional volume integral equation, the surface integral equation reduces greatly the number of unknowns. To computc conducting cavity with electrically large aperture, an electric field integral equation is applied. Some numerical results are given to demonstrate the validity and accuracy of the present methods.

关键词： impedance boundary condition equivalence theory surface integral equation dielectric cavity.

Direction of arrival estimation on cylindrical conformal array using RARE

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Journal of Systems Engineering and Electronics 2011年第5期22卷 767-772页

作者： Kai Yang Zhiqin Zhao Wei Yang zaiping nie School of Electronic Engineering University of Electronic Science and Technology of China Chengdu 610054 E R. China

When the information of mutual coupling and shadowing effect of a conformal antenna array are unknown, the performance of direction of arrival （DOA） estimation will be seriously degraded by using some classical methods, such as the multiple signal classification （MUSIC） algorithm. Meanwhile it is difficult to measure or estimate the shadowing effect. The DOA estimation for a conformal uniform circular array （UCA） is studied. Firstly, the azimuthal angle is separated from all the unknown information by transforming the UCA from the element space to the mode space. Then the rank reduction （RARE） algorithm is applied in the estima- tion of the azimuthal angle. The π ambiguity existed in the RARE is solved by the beam forming. The main advantage of this method is that it does not need to measure the mutual coupling and the shadowing effect. Compared with the subarray method, it will not decrease the aperture of the array. Simulation results validate the advantages of the method.

关键词： conformal antenna direction of arrival mutual coupling.