Smart antennas based on spatial multiplexing of local elements (SMILE) for mutual coupling reduction

A new method for reducing mutual coupling in a smart antenna array using patch antenna elements is proposed. In a recently introduced smart antenna architecture, the spatial multiplexing of local elements (SMILE) scheme, the newly proposed array feed network affects mutual coupling. It is demonstrated that proper design of the feed network may reduce mutual coupling significantly, yielding nearly ideal radiation characteristics. Numerical solutions are used to study and optimize the currents on the surface of a four-element C-band patch antenna array and feed network. Radiation patterns of the same array with different feed networks are also computed. Results show a reduction in sidelobe level of several decibels, increased accuracy in beam pointing during scan, and improved depth and placement.     

Synthesis of onboard array antennas including interaction with themounting platform and mutual coupling effects

The synthesis of array antennas mounted on ships, or any other vehicular platform, is addressed here. Both the mutual coupling between the array elements, and their interaction with the mounting platform, are considered and introduced into the synthesis procedure. This is done by using a three-dimensional formulation of the method of moments, which models the currents induced on the platform and the antennas, combined with an optimization procedure. Some results are presented, illustrating the capability of the proposed synthesis method     

Analysis of injection-locked antenna array including mutual coupling effects

In this paper, the injection locking performance analysis of dipole antenna array with each element loaded with a two-terminal oscillator is presented. The analysis is based on the nonlinear model of oscillator and the linear model of antenna array considering mutual coupling effects. The locking range of injection signal and the array radiated power are obtained by solving an equivalent multiport network. In general, the solutions include stable and unstable solutions. The Routh-Hurwitz stability criterion is then applied to remove the unstable solutions. Numerical results show that the array performance such as frequency locking range and radiated power by taking into account the array mutual coupling effects is quite different from that of an isolated antenna element. In addition, the influence of antenna element spacing upon array locking parameters in this paper is found to be consistent with other existing theories.     

Curvature effects on the mutual coupling of cylindrical-rectangularmicrostrip antennas

The mutual coupling between two cylindrical-rectangular microstrip antennas is studied from the application of the generalised transmission line model (GTLM). Theoretical solutions and measured results of both E-plane and H-plane coupling coefficients are presented. The curvature effects on the mutual coupling are discussed     

Mutual coupling between triangular microstrip antennas on acylindrical body

The full-wave solutions and measured results of mutual coupling coefficients between two cylindrical-triangular microstrip antennas are presented. Both E-plane and H-plane coupling cases are studied. Theory and experiment are in good agreement     

互耦效应对波束赋形天线的影响分析

波束赋形天线技术可以通过基带调零等手段降低干扰信号影响,提升系统抗干扰性能,通过数字信号处理还可以在空间上形成多个波束,从而形成空分多址,大幅度提升系统的容量。但是波束赋形天线技术要求天线间隔尽可能小,一般约为工作频率的半波长,而较小的天线间隔在实际工程实现时会引起严重互相耦合。由于对互耦效应进行有效的数学描述非常困难,一般通过计算量极大的专业天线仿真软件进行仿真验证,严重制约了互耦效应解决方案的提出和论证。文中针对上述问题,提出了互耦效应的数学模型,并利用MATLAB和ANSYS-HFSS工具对相关模型进行了交叉验证。不同平台的对比仿真结果显示了相关模型的正确性和有效性。     

A measurement of the coupling between close-packed shieldedcassegrain antennas

Design and performance details are given for a 0.9-m diameter shielded cassegrain antenna, which will be used in a 13-element close-packed array, The array is designed to make images of brightness fluctuations in the cosmic microwave background radiation. Coupling between a pair of the shielded cassegrain antennas with a separation of 1 m is in the range -110 to -130 dB over the 26- to 36-GHz band     

凸表面上天线间互耦的射线分析法

本文给出了在电尺寸很大的理想导体光滑凸表面上,无限小磁矩或电矩在空间产生的电磁场的近似渐近解,利用该解可以准确有效地计算凸表面上天线间的互耦。此解中,表面塌沿Keller的表面射线路经传播,且在阴影边界过渡区域,包括对于源的邻城,它们仍然一致适用。除此之外,在给出的解中,通过一个系数T/K给出了关于表面场的表面射线绕曲的影响,其中,T表示表面射线的绕曲,K表示射线方向上的表面曲率。该解是由简单的典型问题的近似解导出的。给出了圆柱面和圆锥面上裂缝间互耦的数字结果,它与实验结果相吻合。     

Fundamental superstrate (cover) effects on printed circuit antennas

The fundamental effects of superstrate (cover) materials on printed circuits antennas are investigated. Substrate-superstrate resonance conditions are established which maximize antenna gain, radiation resistance, and radiation efficiency. Criteria are determined for material properties and dimensions for which surface waves are eliminated and a radiation efficiency due to substrate-superstrate effects ofe_{s} = 100percent is obtained. Criteria for nearly omnidirectionalbar{H}-plane patterns and nearly omnidirctionalbar{E}-plane patterns are presented. Finally, a general criterion is given for choosing a superstrate to optimize efficiency for the important case of nonmagnetic layers with the antenna at the interface.     

Hybrid analysis of reflector antennas including higher order interactions and blockage effects

The analysis of a reflector antenna system consisting of a feeder, a sub-reflector, and a main-reflector in microwave frequency bands, where the electrical dimensions of the antenna become prohibitively large for the use of a rigorous numerical method, has been performed by high-frequency asymptotic techniques (HFATs). As a result, the radiation patterns and input impedances of the antenna system were calculated based on an approximation: the radiation characteristics of the feed, sub-reflector and main-reflector are independent from each other. In this study, as an effort to alleviate the inaccuracy due to the exclusion of higher order mutual interactions existing among those subsystems, three different hybrid methods [finite-element method/method of moment (FEM/MOM) + physical optics (PO), FEM/MOM + geometrical theory of diffraction (GTD), and FEM/MOM + PO + physical theory of diffraction (PTD)] are introduced in the context of an iterative algorithm. The interactions between the feed and sub-reflector are accounted by a hybrid method which combines the FEM with the MOM; FEM/MOM. Whereas, the interactions between the objects in the FEM/MOM domain and the main-reflector are taken into account through the iteration: the fields and currents in the FEM/MOM domain are updated using the fields and currents obtained from the HFAT domain and vise-versa. These three methods are applied to two-dimensional reflector configurations, and corresponding results are compared in terms of accuracy and efficiency. The accuracy of the hybrid methods, especially those of FEM/MOM + GTD and FEM/MOM + PO + PTD, is found to be comparable to that of a rigorous numerical method. Furthermore, their computational costs are almost independent to the size of the main-reflector and to the distance from the feed point to the main-reflector.     

Comparative study on the mutual coupling between different sized cylindrical dielectric resonators antennas and circular microstrip patch antennas

A systematic comparative study on the mutual coupling (S/sub 21/) between dielectric resonator antennas (DRAs) and microstrip patch antennas is presented. The mutual coupling between two cylindrical probe-fed DRAs is studied for different radius to height (a/L) ratios. It is found that the mutual coupling decreases with the radius to height ratio. Comparison between mutual coupling of probe-fed cylindrical DRAs and circular microstrip patch antennas with different dielectric substrates are also studied. The mutual coupling between DRAs is 2 dB stronger than between microstrip patch antennas when the patch is etched on a dielectric substrate of a dielectric constant close to the permittivity of the DRA. The mutual coupling of the circular patch antennas reduces with the dielectric constant of the substrate.     

Genetic approach to the minimization of the coupling between aircraft antennas

In this study, the optimization of the electromagnetic interference (EMI) induced by two aircraft onboard VHF–UHF transreceiver antennas is aimed. The EMI reduction is implemented by varying the antenna positions and orientations. The transreceiver antennas are modelled as single monopole antennas therefore the problem is reduced to antenna-to-antenna coupling optimization. The Method of Moments (MoM) is selected for the EMI analysis and the continuous parameter Genetic Algorithm (CPGA) is chosen for the optimization method. The results of the numerical analysis are verified by the measurement on a 1:10 scaled model in an anechoic chamber.     

Gaussian beam mode analysis of the coupling of power between horn antennas

Gaussian beam mode analysis can be applied in an elegant way to study the coupling of power between two horn antennas. Coupling efficiencies are evaluated for a number of horn combinations and the results presented in a straightforward form useful in the design of submillimetre-wave interferometers and astronomical receiver systems. We show that there is a marked variation in efficiency (up to 30%) depending on the coupling optics, even for beams with well matched profiles.     

Adaptive algorithm of direct data domain including mutual coupling effects

An adaptive algorithm of direct data domain including mutual coupling effects is presented. Numerical simulation shows that this algorithm can recover the desired signal accurately in the presence of mutual coupling. Since the mutual coupling effects are included in the adaptive algorithm automatically, compensation on the receiving signal is then no longer required.     

Study of the coupling between human head and cellular phone helical antennas

The interaction between normal-mode helical antennas and human head models is analyzed, using both a novel accurate semi-analytical method and finite-difference time-domain (FDTD) simulations. The semi-analytical method is based on the combination of Green's functions theory with the method of moments (Green/MoM) and is able to model arbitrarily shaped wire antennas radiating in the close proximity of layered lossy dielectric spheres representing simplified models of the human head. The purpose of the development of the Green/MoM technique is to provide a reliable tool for preliminary (worst case) estimation of human head exposure to the field generated by different antenna configurations with emphasis on the helical antenna, representing the most diffused antenna type used in modern cellular handsets. Furthermore, the accurate semi-analytical character of the Green/MoM technique permits the accuracy assessment of purely numerical techniques, such as the FDTD, which is currently the most widely used computational method in mobile communication dosimetric problems, since it allows modeling of anatomically based head models. After appropriate benchmarking, FDTD simulations are used to study the interaction between a heterogeneous anatomically correct model of the human head exposed to a normal-mode helix monopole operating at 1710 MHz mounted on the top of a metal box representing a realistic mobile communication terminal. The study of both canonical and realistic exposure problems includes computations of specific absorption rates (SARs) inside the human head, total power absorbed by the head and assessment of antenna performance. Emphasis is placed on the comparative dosimetric assessment between adults and children head models.     

Mutual coupling between metal strip antennas on finite size,electrically thick dielectric substrates

An analysis of the mutual coupling between metal strip antennas which are contiguous with the ends of finite-size, electrically thick dielectric substrates is outlined. Such antennas have been proposed as useful monolithic microwave integrated circuit antennas for millimeter-wavelength applications. The analysis presented was verified experimentally, and the results are applied to three-element arrays of metal strip folded dipoles with coplanar strip feed lines. The effect of the electrically thick, finite-size dielectric substrates on the mutual coupling between elements of the arrays is described     

Comparison of measured and calculated mutual coupling in the near field between microwave antennas

Measurements of near-field mutual coupling between two moderate sized microwave antennas were performed and compared to coupling calculated using recently developed computer programs. Required input data for the programs are the complex far-field radiation patterns of the antennas and various geometrical factors describing the relative positions and orientations of the two antennas. Measured and calculated coupling as a function of both transverse and radial displacement showed good agreement.     

随机相位误差对相控阵天线的性能影响

为了对随机相位误差对于相控阵天线波束指向精度和副瓣电平的影响进行分析,以一维均匀直线阵为模型,采用概率统计的手段对波束指向误差的数学期望、方差和峰值副瓣电平进行了推导,并对此结果进行了计算机仿真验证和比较.仿真结果表明,理论公式推导得到的结论与仿真实验的各项结果吻合良好.