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.     

Mutual coupling between reduced surface-wave microstrip antennas

An investigation of the mutual coupling between reduced surface-wave microstrip antennas is presented and compared with that for conventional microstrip antennas. Numerical results are presented from a theoretical analysis of the mutual coupling along with confirming experimental results. It is shown that for electrically thin substrates, the space-wave coupling, not the surface-wave coupling, is predominant for typical element spacing, for both the conventional and reduced surface-wave antennas. In addition, the mutual coupling behavior is examined using an asymptotic analysis, which demonstrates how the coupling falls off much faster with patch separation for reduced surface wave antennas compared to conventional microstrip patch antennas     

A mutual coupling study of linear and circular polarized microstrip antennas for diversity wireless systems

In this paper, an analysis of mutual coupling is presented to examine the benefits of orthogonal polarizations and patterns for adjacent microstrip antennas. The mutual coupling between two linear polarized antennas orientated in parallel polarizations (E and H plane) is reduced using low dielectric constant materials. The mutual coupling can be reduced an additional 20-35dB at the same inter-element spacing when adjacent elements are orientated in orthogonal polarizations, O plane. Similarly, the mutual coupling between two circular polarized antennas orientated in the parallel polarization is reduced using low dielectric constant materials. However, the reduction in mutual coupling between two circular polarized antenna elements orientated in the O plane is only an additional 1-6 dB. The mutual coupling between a linear polarized sum beam (1/2/spl lambda/) and difference beam (1/spl lambda/) antenna is reduced 20-35 dB below the case when using identical antennas only in the H- and O-planes. Compact two- and four-element multielement antennas with inter-element spacings less than 0.15/spl lambda/ are fabricated and the S parameters and radiation patterns are measured.     

Theory of mutual coupling among minimum-scattering antennas

A novel and rigorou formulation for mutual impedance among a class of idealized but realizable antennas is presented. Unlike past treatments of mutual coupling, which have proceeded from structurally specified antennas, the present treatment deals with a class of antennas, all the electromagnetic properties of which are rigorously expressed explicitly in terms of their radiation patterns alone. Employing a network formulation based on a scattering representation of electromagnetic fields in terms of spherical (or cylindrical) modes, the mutual impedances between such antennas are computed exactly. Several alternate representations for the mutual impedance are derived, one of which is an integral representation involving the power pattern function for both real and complex angles. In special cases, these exact results agree with published results obtained by applying well-known approximate techniques to structurally specified antennas. An important and illuminating example is provided by an infinite planar array of antennas radiating into a half-space for which the present formulation yields the well-known grating-lobe series representation of the active impedance without an explicit reference to structural properties of the radiating elements.     

A numerical technique for calculating mutual impedance and element patterns of antenna arrays based on the characteristics of an isolated element

A numerical technique for calculating mutual impedance and element patterns of antenna arrays based on the characteristics of an isolated element is presented. The basis for this technique is the theory of minimum-scattering (MS) antennas and, in particular, the interpretation of the mutual impedance between two canonical minimum-scattering (CMS) antennas as the first term in a perturbation series of the mutual impedance of arbitrary antennas. For the computation of the mutual impedance via the CMS approximation this pattern must be continued analytically into the complex domain. However, numerical codes provide radiation patterns only for real observation angles. To overcome this problem, the numerically calculated patterns are expanded in terms of spherical modes and the computation over complex angles is carried out analytically. Numerical results for collinear and linear arrays of parallel electric dipole antennas and rectangular probe-fed patch antennas are presented and a comparison is made with direct calculations using the WIPL-D code. Results presented show the good agreement between the CMS approximation and the WIPL-D code.     

Correlation and capacity of MIMO systems and mutual coupling, radiation efficiency, and diversity gain of their antennas: simulations and measurements in a reverberation chamber

MIMO systems are characterized by their maximum available capacity, which is reduced if there is correlation between the signals on different channels. The correlation is primarily caused by mutual coupling between the elements of the antenna arrays on both the receiving and transmitting sides. Similarly, diversity antennas can be characterized by a diversity gain that also is affected by mutual coupling between the antennas. We explain how such MIMO and diversity antennas with mutual coupling can be analyzed by classical embedded element patterns that can be computed by standard computer codes. In the MIMO example under investigation, the mutual coupling reduces both correlation, which increases the capacity, and radiation efficiency, which decreases it, and the combined effect is a net capacity reduction. We also explain how the radiation efficiency, diversity gain, correlation, and channel capacity can be measured in a reverberation chamber. The measurements show good agreement with simulations.     

Antenna diversity in mobile communications

The conditions for antenna diversity action are investigated. In terms of the fields, a condition is shown to be that the incident field and the far field of the diversity antenna should obey (or nearly obey) an orthogonality relationship. The role of mutual coupling is central, and it is different from that in a conventional array antenna. In terms of antenna parameters, a sufficient condition for diversity action for a certain class of high gain antennas at the mobile, which approximates most practical mobile antennas, is shown to be zero (or low) mutual resistance between elements. This is not the case at the base station, where the condition is necessary only. The mutual resistance condition offers a powerful design tool, and examples of new mobile diversity antennas are discussed along with some existing designs.     

Comparison of mutual coupling of blade antennas with predictionsbased on minimum-scattering antenna theory

The utility of the minimum-scattering antenna model in describing the mutual coupling between two L-band aircraft blade antennas is examined. The communication and sensor requirements of many aircraft, particularly those used by the military, frequently necessitate antennas being placed in close proximity to one another. For such cases, the relatively simple minimum-scattering antenna model provides a very good approximation of the measured mutual coupling of blade antennas and eliminates the need for solving coupled integral equations     

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     

复杂平台天线间耦合度预测的逐级等效法

复杂平台天线间耦合度计算是系统级电磁兼容研究的重要课题,给出一种解决复杂平台天线间耦合度问题的新方法——逐级等效法。逐级等效法把原始求解区域分成三个分区逐级求解,在求解一个区时,把上一区的等效源作为此区的激励源,最终求得天线间耦合度。通过此方法降低了每次运算时的计算量,使得许多原来不能计算的问题得到解决。为了验证方法的正确性,举例计算了一平台上天线间的耦合度,结果与矩量法计算的统一模型做了对比。最后以某大型战斗机上两天线间的耦合度为例,用逐级等效法解决了这一普通算法在现有计算机配置下很难计算的问题。     

自适应天线中阵元间互耦的校正＊

本文基于对自适应天线协方差矩阵特征结构的分析,推导出了考虑阵元间互耦时的自适应天线最佳权矢量的解析表达式。阐明了互耦导致自适应天线系统性能下降的机制,最后提出了一种有效的互耦校正方法。     

Experimental verification of the reduction of coupling between dipole antennas by using a woodpile substrate

In this paper, the mutual coupling between dipole antennas placed on top of a woodpile structure is experimentally investigated. The coupling between dipoles backed by a woodpile substrate is compared with that obtained when the dipole antennas are placed on a dielectric substrate and when they radiate into free space. On average, between 2 and 7 dB reduction of the mutual coupling is achieved with respect to the dielectric substrate case when the woodpile substrate is used. The free space coupling is also reduced in the H-plane configuration case. However, the E-plane coupling slightly increases due to modification of the radiation pattern. Imaging array applications could potentially benefit from the use of EBG substrates due to the improved isolation between pixels.     

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 microstrip antennas

A theoretical study of mutual coupling between microstrip antennas is presented. The cavity method is used, and from the equivalence theorem application the problem is reduced to interaction of two magnetic loops. The mutual impedance is then calculated from the reaction theorem. Theoretical results and measurements are in good agreement.     

Comments on “Anomalous mutual coupling between microstripantennas” [and reply]

The paper by Haddad and Pozar (see ibid., vol.42, no.11, p.1545, 1994) contains important observations about the mutual coupling between printed antennas. It presented the oscillatory behavior of the mutual coupling between two printed dipoles as the separation between elements is increased. The authors used a closed form asymptotic Green's function to evaluate the mutual impedance between the elements. The oscillatory behavior of the mutual coupling is supposed to be a consequence of the interference between the surface waves and the space waves. The authors of the aforementioned paper stated that this behavior was previously unreported. Rosales here comments that the "anomalous" oscillatory behavior of the mutual coupling between microstrip antennas was in fact reported in a paper presented at the Ninth Computing Conference on the Computation of Electromagnetic Fields, and by Haddad and Pozar in their paper, almost simultaneously. The results and conclusions of both papers confirm each other. Haddad and Pozar reply to the Comment     

High mutual coupling reduction between microstrip patch antennas using novel structure

In this paper, a novel parasitic configuration to reduce the mutual coupling between two adjacent microstrip patch antennas is presented. It is shown that mutual coupling between the antenna elements can be reduced significantly by two simple slots structure on the ground plane and several shorted simple conducting strips between patch antennas. The structure has been constructed and tested. Both simulated and measured results are presented. The results are shown that more than 7 dB reduction within operational frequency bandwidth with the maximum 41 dB mutual coupling at center frequency can be achieved. The measurement results prove the high efficiency of this configuration in multi antenna systems.     

Application of the minimum scattering antenna theory to mismatched antennas

The mutual impedance between canonical minimum scattering (CMS) antennas can be calculated directly from their far-field radiation patterns. While having the potential to greatly simplify array analysis and design, the theory has limited practical applicability because, by definition, CMS antennas are matched to their terminations. It is shown here that the theoretical basis of the mutual coupling calculation does not require the antennas to be matched and that the theory is simply extended to mismatched antennas. The only requirement is that the antennas are invisible, i.e., do not scatter, when open-circuited. This does not impose a greater restriction on the practical applicability of the method, since characteristic mode theory indicates that dipoles and loops, and perhaps other antennas, can be made very nearly invisible by a suitable reactive termination if the frequency is near or below first resonance. A new antenna, consisting of the original antenna plus a particular length of transmission line, will then be almost invisible on open circuit. The theory is applied to calculating the active impedance in an array of small monopole-like elements in a parallel plate waveguide and the results compared with experiment.     

背腔式缝隙天线混合方法降耦研究

运用混合降耦方法,提出了一种简单但高效率的减小背腔式缝隙天线耦合的结构,通过放置两对称寄生单元和去介质的降耦方法,经点频优化,与无附加结构的天线相比,在反射系数小于-10dB 的1. 7% 带宽范围内(中心频率为12GHz)互耦降低了9. 7dB,天线的方向图得到了改善,端射方向的能量减小。在点频优化的基础上,通过带宽内的优化进一步改善了耦合性能,在反射系数小于-10dB 的2. 2%带宽范围内互耦降低了11. 5dB。该降耦方法结构简单、成本低、易加工。     

An analysis of antenna coupling between arrays on a polyhedronstructure

Antenna coupling between arrays on a polyhedron structure is investigated. First of all, a high-frequency asymptotic closed-form formula is derived for the mutual admittance between two linearly polarized circular microstrip antennas located on the different faces of a perfectly conducting wedge. The microstrip antennas are modeled by the cavity model, and the mutual coupling caused by the wedge-diffracted field is analyzed by the EMF method using Keller's GTD diffraction coefficients for the diffracted field. Next, the antenna coupling between arrays is calculated and compared with an experimental result. Good agreement between them supports the theory. Finally, the properties of the antenna coupling are described by some numerical simulations     

共享孔径交错稀疏阵列天线互耦误差建模与校正

共享孔径交错稀疏阵列天线是实现多功能阵列天线的有效途径。现有的参数化互耦消除方法都是针对均匀阵列天线展开的,其研究的互耦矩阵都是规则的方阵,对共享孔径交错稀疏阵列天线的互耦矩阵模型并不适用。在充分考虑共享孔径交错稀疏阵列天线中子阵内互耦的“稀疏”和“方位依赖”的特殊性后,通过将常规的互耦矩阵扩展表示为“非方”的“增广互耦矩阵”来对交错稀疏阵列天线子阵内和子阵间的耦合效应进行建模,并通过“增广互耦矩阵”的参数化估计最终实现了共享孔径交错稀疏阵列天线互耦误差的建模与校正。仿真结果证实了所提方法的有效性和可行性。