Triangular quad-port multi-polarized UWB MIMO antenna with enhanced isolation using neutralization ring

In this study, a quad-port multi-polarized ultra-wideband (UWB) multiple input multiple output (MIMO) antenna system with a new isolation technique is designed for wireless devices. The antenna structure consists of four triangular monopole elements and neutralization ring (NR) structures. The monopoles are back-to-back positioned in symmetrical and orthogonal arrangement. Therefore, they radiate towards four directions without interference, and thus the diversity performance is improved. A novel NR is formed by combining a rectangular ring and a straight line to reduce the mutual coupling due to interoperation of the elements. Each triangular monopole is fed by 50 Ohm microstrip transmission line (MTL) with a thin strip line for ensuring impedance matching. Antenna performance in terms of impedance bandwidth, current distribution, radiation pattern, peak gain and envelope correlation coefficient (ECC) is also investigated. The MIMO antenna system has 3.1–17.3 GHz impedance bandwidth, 1–5 dBi peak gain variation, less than 0.1 ECC. The results indicate that the proposed antenna has the characteristics of larger UWB bandwidth, high isolation by the NR structure, multi-polarization, uniform gain and quasi-omnidirectional pattern.     

MIMO Channel Capacity and Configuration Selection for Switched Parasitic Antennas

Multiple-input multiple-output (MIMO) systems offer significant enhancements in terms of their data rate and channel capacity compared to traditional systems. However, correlation degrades the system performance and imposes practical limits on the number of antennas that can be incorporated into portable wireless devices. The use of switched parasitic antennas (SPAs) is a possible solution, especially where it is difficult to obtain sufficient signal decorrelation by conventional means. The covariance matrix represents the correlation present in the propagation channel, and has significant impact on the MIMO channel capacity. The results of this work demonstrate a significant improvement in the MIMO channel capacity by using SPA with the knowledge of the covariance matrix for all pattern configurations. By employing the “water-pouring algorithm” to modify the covariance matrix, the channel capacity is significantly improved compared to traditional systems, which spread transmit power uniformly across all the antennas. A condition number is also proposed as a selection metric to select the optimal pattern configuration for MIMO-SPAs.     

Broadband bowtie belt nanoantennas

In this article, we study a linear array of bowtie nanoantennas placed between two metallic strips that can work from 800 to 1420 nm (600 nm linewidth), with an electric field enhancement factor close to 20. We study the dynamical change of the position of the electric field enhancement amongst different elements in the array and, at the same time, the effects of dispersion on the scalability of the array elements. A systematic analysis and methodology to produce an array that can operate over a large bandwidth whilst maintaining the electric field enhancement without significant variation is provided.     

恒模信号波达方向和阵列天线互耦系数的联合估计算法

提出了1种针对恒模信号的波达方向和阵列天线互耦系数的联合估计算法。新算法不需要方位已知的辅助校正源,可以在线完成实际信源的方位估计。仿真结果证明了新算法的估计精度取决于信源的信噪比、方位组合和快拍数等因素。     

Scheme for antenna design used in in-band full-duplex communication

In order to effectively suppress the self-interference of the in-band full-duplex communication system, a solution for designing the transceiver antenna based on the simple ring structure and collinear dipole is proposed. In this design, two printed dipole antennas are placed in the zero radiation direction of each other to achieve low port isolation between the two transceiver antennas. Then a simple ring structure is added to improve the isolation between the two antennas. Experimental results show that the two transceiver antennas designed by this scheme have omnidirectional radiation characteristics and can obtain a high port isolation of better than 45.9 dB in 2.4~2.6 GHz band. The scheme for designing the transceiver antenna proposed in this paper can not only effectively reduce the interference between two transceiver antennas, but also provide omnidirectional signal coverage. It is an effective solution for designing transceiver antennas for the in-band full-duplex communication system.     

Proximity effects of a layered periodic structure on miniaturization of patch antennas

A miniaturized microstrip antenna on a planar layered periodic structure is proposed, designed and fabricated. The proposed structure miniaturizes patch antennas in the microwave band. With varying the parameters of the proposed structure, the achieved miniaturization factor can be adjusted in the range 2.6–4.2. Numerical and experimental results are presented. © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2013.     

TLM modeling of a probe‐coupled cylindrical cavity based on compact wire model in the cylindrical mesh

This article describes an implementation of a compact wire model into the three‐dimensional transmission‐line matrix (TLM) cylindrical mesh for the purpose of an efficient analysis of probe‐coupled cylindrical microwave cavity devices. Because of a cylindrical grid structure and empirical nature of the compact model, this implementation has to take into account a change of wire model parameters with a variable cross section of the TLM nodes through which a wire conductor passes. The model accuracy has been experimentally verified and compared with the corresponding results reached by the TLM method based on a rectangular grid in order to consider its advantages. © 2011 Wiley Periodicals, Inc. Int J RF and Microwave CAE, 2012.     

粒子群阵列天线方向图适应值函数研究

在粒子群算法优化阵列天线方向图时,适应值函数的选取对算法收敛和优化效率都有着至关重要的影响。针对复杂多指标方向图优化容易早熟收敛,提出了一种分步的适应值函数策略,通过分阶段提高优化指标,可以更好地促进算法收敛和提升优化效率。仿真结果表明:将此适应值策略应用于天线方向图综合中,在不改变算法本身的同时,可以在多零点和低旁瓣约束情况下取得更好的优化效果。     

阵列天线相位中心的测量方法研究

提出了一种测量阵列天线相位中心的方法。首先,根据阵列天线的基本原理,推导出了阵列天线相位方向图与相位中心偏移量的关系式;再结合相位中心的定义和实际测量的步骤,运用最小二乘法及其矩阵解形式计算出了相位中心的精确值;最后对提出的测量方法进行了模拟实验验证。实验证明,该测量方法可以精确地计算出相位中心的位置,并发现计算结果与测量时的读数精度有很大关系。当读数精度达到百分位时,校准误差仅为0.168%。     

双发射天线对混响室场性能影响的数值分析

提出了双天线激励混响室的方法,研究了双天线激励对混响室场性能的影响。分析了双天线改善混响室场均匀性的原理,对单天线激励下的混响室模型以及处于不同位置的双天线激励下的混响室模型进行了仿真计算,从场均匀性和场强两个方面研究了双天线对混响室场性能的影响,对双天线影响场强的机理进行了分析。研究表明:采用双天线激励改善了混响室工作区域的场均匀性;采用双天线可以降低对功率放大器的要求,降低大型混响室测试成本。最后对双发射天线在大型混响室中的应用进行了探讨和展望。