Low spatial correlation at base station uniform linear antennas

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.

Quantum-Inspired Equilibrium Optimizer for Linear Antenna Array

With the rapid development of communication technology,the problem of antenna array optimization plays a crucial role.Among many types of antennas,line antenna arrays(LAA)are the most commonly applied,but the side lobe level(SLL)reduction is still a challenging problem.In the radiation process of the linear antenna array,the high side lobe level will interfere with the intensity of the antenna target radiation direction.Many conventional methods are ineffective in obtaining the maximumside lobe level in synthesis,and this paper proposed a quantum equilibrium optimizer(QEO)algorithm for line antenna arrays.Firstly,the linear antenna array model consists of an array element arrangement.Array factor(AF)can be expressed as the combination of array excitation amplitude and position in array space.Then,inspired by the powerful computing power of quantum computing,an improved quantum equilibrium optimizer combining quantum coding and quantum rotation gate strategy is proposed.Finally,the proposed quantum equilibrium optimizer is used to optimize the excitation amplitude of the array elements in the linear antenna array model by numerical simulation to minimize the interference of the side lobe level to the main lobe radiation.Six differentmetaheuristic algorithms are used to optimize the excitation amplitude in three different arrays of line antenna arrays,the experimental results indicated that the quantum equilibrium optimizer is more advantageous in obtaining the maximum side lobe level reduction.Compared with other metaheuristic optimization algorithms,the quantum equilibrium optimizer has advantages in terms of convergence speed and accuracy.

Formulation of Optimization Problems with Radiation Field Phases as Design Variables for Pattern Synthesis of Linear Antenna Arrays

Pattern synthesise of antenna arrays is usually complicated optimization problems,while evolutionary algorithms(EAs)are promising in solving these problems.This paper does not propose a new EA,but does construct a new form of optimization problems.The new optimization formulation has two differences from the common ones.One is the objective function is the field error between the desired and the designed,not the usual amplitude error between the desired and the designed.This difference is beneficial to decrease complexity in some sense.The second difference is that the design variables are changed as phases of desired radiation field within shaped-region,instead of excitation parameters.This difference leads to the reduction of the number of design variables.A series of synthesis experiments including equally and unequally spaced linear arrays with different pattern shape requirements are applied,and the effectiveness and advantages of the proposed new optimization problems are validated.The results show that the proposing a new optimization formulation with less complexity is as significant as proposing a new algorithm.

Effects of Spatial Characteristics on Smart Antenna System with Uniform Linear Antenna Array

The effect of the spatial characteristics of antenna array on smart antenna systems can not be neglected. In the paper, the relation between spatial correlation and inter-antenna distance, impinging angle, angle spread is first investigated. With the same beam forming algorithm, we simulate the performance of smart antenna system with different Angle Spread （AS） values on the conditions of ideal and real Angle of Arrival （AOA） estimation. The results show that with the ideal AOA estimation, the AOA is enough accurate to guarantee that the system only has little performance degradation even in the case of 20 degreee AS value while the real AOA estimation influenced by channel environment degrades the performance very obviously, up to about 7 dB.

Optimal array factor radiation pattern synthesis for linear antenna array using cat swarm optimization： validation by an electromagnetic simulator

In this paper, an optimal design of linear antenna arrays having microstrip patch antenna elements has been carried out Cat swarm optimization （CSO） has been applied for the optimization of the control parameters of radiation pattern of an antenna array. The optimal radiation patterns of isotropic antenna elements are obtained by optimizing the current excitation weight of each element and the inter-element spacing. The antenna arrays of 12, 16, and 20 elements are taken as examples. The arrays are designed by using MATLAB computation and are validated through Computer Simulation Technology-Microwave Studio （CST-MWS）. From the simulation results it is evident that CSO is able to yield the optimal design of linear antenna arrays of patch antenna elements.

Length minimization of uniform linear antenna array for millimeter wave communications with maximum capacity

For uniform linear antenna array （ULA） based millimeter wave communications, the maximum capacity can be achieved by the optimal antenna separation product （ASP）. However, due to the practical size limitation, it is necessary to decrease the ULA length. In this paper, an optimization problem is formulated to minimize the ULA length for millimeter wave communications with maximum capacity. We decompose the problem into two subproblems： length selection optimization and orientation deployment optimization. The optimal length selection can be obtained when the transmit and receive ULAs have equal length. By using the property of trigonometric function, we derive the optimal orientation deployment and study the influence of orientation deviation on ULA length. Simulation results are presented to validate the analyses.

New Antenna Array Beamforming Techniques Based on Hybrid Convolution/Genetic Algorithm for 5G and Beyond Communications

Side lobe level reduction(SLL)of antenna arrays significantly enhances the signal-to-interference ratio and improves the quality of service(QOS)in recent and future wireless communication systems starting from 5G up to 7G.Furthermore,it improves the array gain and directivity,increasing the detection range and angular resolution of radar systems.This study proposes two highly efficient SLL reduction techniques.These techniques are based on the hybridization between either the single convolution or the double convolution algorithms and the genetic algorithm(GA)to develop the Conv/GA andDConv/GA,respectively.The convolution process determines the element’s excitations while the GA optimizes the element spacing.For M elements linear antenna array(LAA),the convolution of the excitation coefficients vector by itself provides a new vector of excitations of length N=(2M−1).This new vector is divided into three different sets of excitations including the odd excitations,even excitations,and middle excitations of lengths M,M−1,andM,respectively.When the same element spacing as the original LAA is used,it is noticed that the odd and even excitations provide a much lower SLL than that of the LAA but with amuch wider half-power beamwidth(HPBW).While the middle excitations give the same HPBWas the original LAA with a relatively higher SLL.Tomitigate the increased HPBWof the odd and even excitations,the element spacing is optimized using the GA.Thereby,the synthesized arrays have the same HPBW as the original LAA with a two-fold reduction in the SLL.Furthermore,for extreme SLL reduction,the DConv/GA is introduced.In this technique,the same procedure of the aforementioned Conv/GA technique is performed on the resultant even and odd excitation vectors.It provides a relatively wider HPBWthan the original LAA with about quad-fold reduction in the SLL.

A Linear Array Antenna of Microstrip Patch Antennas Fed by the Open-End of Coplanar Waveguides

In this study, we constructed a 4-element linear array antenna using four 20 GHz band microstrip patch antennas with a structure such that the signal is fed to the patch antennas from open-end coplanar waveguides without contact. We investigated factors related to the design of linear array patch antennas. To adjust the maximum radiation direction and reduce return loss, we optimized the spacing between the elements and their shape. With an element spacing of 11.50 mm, patch width of 3.90 mm, and patch length of 4.15 mm, we obtained a resonance frequency of 20.05 GHz and a return loss of -29.59 dB at the resonance frequency. However, in the case of a 4-element linear array antenna structure, undesired resonances occurred in frequency bands other than the design resonance frequency band of 20 GHz. To suppress these undesired resonances and obtaining stable operation at the design frequency, we propose a new structure in which the feed line is loaded with a short stub, and show through computer simulations that the occurrence of undesired resonances can be sufficiently suppressed. Furthermore, we demonstrate the problem of radiation gain reduction caused by introducing a short stub, propose a design method for a new structure in which the feed line has slits between the stubs, and show improvement of the antenna gain by 0.5 dBi.

Improved Measurement Method of Circularly-Polarized Antennas Based on Linear-Component Amplitudes

An improved measurement method of circularly-polarized (CP) antennas based on linear-component amplitudes is proposed in this paper. By utilizing two sets of orthogonal linear polarization (LP) amplitudes, measurement on axial ratio (AR) of CP antennas can be realized without phase information. However, the rotation sense of the co-polarization cannot be determined due to the absence of the phase information. Above problem is discussed here for the first time, and a solution is presented to determine the rotation sense of the co-polarization by using common auxiliary CP antennas. In addition, there will be some particular cases with large errors in actual measurement. Here a corresponding solution method is given. Finally, co-polarization and cross-polarization patterns can be further obtained from AR results. To verify this improved method, a self-developed CP microstrip array was measured. The measured results are in agreement with the simulated results, which prove this method is correct, effective and practical.

Experimental Study of Parameters of a Plasma Antenna

A plasma column excited by a surface wave can act as a plasma antenna. Experiments are carried out to study the current and conductivity distributions, field, power patterns, directivity and efficiency of such a plasma antenna. In addition, an equivalent metallic copper antenna is built up and its antenna parameters are compared with that of the plasma antenna. Our findings indicate that the power content in the harmonics of the plasma antenna is more prominent as compared to the copper antenna （which only generates a fundamental frequency）. However, the power patterns for both antennae are quite similar. To provide a more qualitative understanding regarding the generation of harmonics in the field of the plasma antenna, a bi-spectral analysis is performed to study the nonlinear interactions in the current fluctuations. Some specific features of the plasma antenna are investigated in our study, which may enhance the application prospect of the plasma antenna with respect to the conventional metallic antenna.

On an MC-CDMA System Operating with Distinctive Scenarios of Antenna

In this paper the impact of distinctive structure of antenna with branch correlation for an OFDM (orthogonal frequency division multiplexing)-based system, MC-CDMA (multi-carrier coded-division multiple-access) system, operating over the frequency selective fading environments is studied. For the reason of accordance with the working environments in the real world applications (urban areas) the correlated-Nakagami-m fading is adopted. Furthermore, the performance evaluation with average BER (bit error rate) formulas of MC-CDMA system with MRC (maximal ratio combining) diversity was derived with an alternative method of the complementary error function. The illustrated results are not only discussing the effect that comes from triangular, linear, and circular antenna array constructions, but the factors of branch correlation are also analyzed. Generally, it is known that the more the received branch number is, the more superior system performance of a multiple-access system will become. It is interesting to contrast to the geometric of the antenna array, that is, the little shape changing of the antenna is, the worse inferior system performance arrive at.

Numerical Modeling and Computer Simulation of a Meander Line Antenna for Alzheimer’s Disease Treatment, a Feasibility Study

Alzheimer’s disease (AD) is a brain disorder that eventually causes memory loss and the ability to perform simple cognitive functions;research efforts within pharmaceuticals and other medical treatments have minimal impact on the disease. Our preliminary biological studies showed that Repeated Electromagnetic Field Stimulation (REFMS) applying an EM frequency of 64 MHz and a specific absorption rate (SAR) of 0.4 - 0.9 W/kg decrease the level of amyloid-β peptides (Aβ), which is the most likely etiology of AD. This study emphasizes uniform E/H field and SAR distribution with adequate penetration depth penetration through multiple human head layers driven with low input power for safety treatments. In this work, we performed numerical modeling and computer simulations of a portable Meander Line antenna (MLA) to achieve the required EMF parameters to treat AD. The MLA device features a low cost, small size, wide bandwidth, and the ability to integrate into a portable system. This study utilized a High-Frequency Simulation System (HFSS) in the design of the MLA with the desired characteristics suited for AD treatment in humans. The team designed a 24-turn antenna with a 60 cm length and 25 cm width and achieved the required resonant frequency of 64 MHz. Here we used two numerical human head phantoms to test the antenna, the MIDA and spherical head phantom with six and seven tissue layers, respectively. The antenna was fed from a 50-Watt input source to obtain the SAR of 0.6 W/kg requirement in the center of the simulated brain tissue layer. We found that the E/H field and SAR distribution produced was not homogeneous;there were areas of high SAR values close to the antenna transmitter, also areas of low SAR value far away from the antenna. This paper details the antenna parameters, the scattering parameters response, the efficiency response, and the E and H field distribution;we presented the computer simulation results and discussed future work for a practical model.

Optimization Algorithms for Sidelobes SSL Reduction: A Comparative Study

The development of new technologies in smart cities is often hailed as it becomes a necessity to solve many problems like energy consumption and transportation. Wireless networks are part of these technologies but implementation of several antennas, using different frequency bandwidths for many applications might introduce a negative effect on human health security. In wireless networks, most antennas generate sidelobes SSL. SSL causes interference and can be an additional resource for RF power that can affect human being health. This paper aims to study algorithms that can reduce SSL. The study concerns typical uniform linear antenna arrays. Different optimum side lobe level reduction algorithms are presented. Genetic algorithm GA, Chebyshev, and Particle Swarm Optimization algorithm are used in the optimization process. A comparative study between the indicated algorithms in terms of stability, precision, and running time is shown. Results show that using these algorithms in optimizing antenna parameters can reduce SSL. A comparison of these algorithms is carried out and results show the difference between them in terms of running time and SSL reduction Level.

一种等通量波束的多极化可重构天线

随着航天技术的革新,对近地轨道的通信需求逐年增高。近地轨道卫星就在此背景下产生,主要应用于遥感探测天气预报和数据通信领域。由于近地轨道卫星天线辐射波束所覆盖的地球表面是球面,因此波束通常设计为等通量形式。由于卫星通信通常存在极化失配、多径效应等问题,选择多极化而不是圆极化作为近地卫星天线的工作状态能更好地适应复杂的工作环境,保证通信质量,将等通量波束天线和多极化可重构技术结合起来有很大的应用前景。基于一对正交圆极化波能合成线极化波的设计原理,文中提出了一种具有等通量波束的多极化可重构天线,该天线由可重构馈电网络和带扼流环的隔片极化器圆波导组成。馈电网络中嵌入单刀四掷开关(SP4T)与单刀双掷开关(SP2T),通过改变开关的工作状态,馈电网络将给圆波导提供不同的馈电条件,在圆波导内隔片的作用下天线实现两种圆极化与两种线极化的可重构。通过在圆波导口引入扼流环以及波导口作“T”型开槽处理,实现波束赋形,并且保证天线在不同极化状态下辐射等通量波束。实测结果显示,天线在不同的极化状态下-15 dB重叠阻抗带宽14.7%,覆盖4.80~5.56 GHz,方向图顶部在θ为-24°~+24°范围内具有平坦效果,圆极化状态下空间轴比覆盖-51°~+50°,覆盖范围大于方向图顶部平坦范围。天线实测结果与仿真结果有较好的一致性,具有多极化和方向图顶部平坦的优势,可满足移动通信和卫星通信中多极化应用场景的需要。

基于权重系数调控的阵列天线阵元方向布局优化

研究建立了一种基于权重系数调控的阵列天线阵元方向布局优化方法。该方法以阵列天线最大增益和最大旁瓣之差的加权和为适应度函数,通过合理选取主辐射方向增益与最大旁瓣之差和最大增益的权重系数,实现了阵列天线高增益、低旁瓣的设计需求,讨论了不同权重系数下的优化结果,并总结了权重系数调控阵列天线辐射性能的规律。采用基于矩量法的全波分析方法进行分析,充分考虑了阵列天线各阵元耦合场的影响。基于遗传算法求解了该文提出的优化问题,并实现了线性和平面偶极子阵列天线各阵元方向布局的优化设计。结果表明,当线性和平面阵列天线方向布局优化设计的权重系数分别取0.45和0.9时,所建立的优化方法不仅降低了旁瓣电平和交叉极化增益,并且能够保证主辐射方向增益下降不大,从而验证了该方法的可行性和有效性。

高铁5G天线技术及选型应用分析

5G网络高频段高穿损特征带来站址数量增加的压力,为降低工程选址难度,同时提升高铁场景的5G覆盖性能,本文从分析高铁5G天线入手,指出了5G站间距小于4G网络、以及传统天线在线性道路覆盖存在的远近效应影响是高铁5G网络性能的重要因素。本文详细阐述了天线波束调整能力增强技术和实现方案,并以测试实例验证了这种技术在高铁组网时的性能提升效果。考虑到工程应用需求,本文还对比了不同实现方案在覆盖性能、造价和工程应用等方面的差异,提出高铁场景下的5G天线选型应用建议。

基于多种群竞争差分进化算法的稀布线阵优化

为进一步降低差分进化算法及其改进算法优化稀布线阵时的峰值旁瓣电平,提出了一种基于多种群竞争的差分进化算法。用多个亚种群代替单一种群,借鉴竞争机制对亚种群进行评估,根据评估得分确定各亚种群产生新个体的数量,分数高的亚种群可以产生更多新个体,体现出高质量亚种群的优势。引入信息交流行为将这种优势扩散到其他亚种群,加快整个种群的收敛速度,提高解的质量。对亚种群评估和信息交流行为的机制分析以及实验验证表明,2种行为结合使用算法性能最佳。3种天线实例仿真实验表明:与对比算法中最优算法相较,所提方法50次实验的平均峰值旁瓣电平分别降低了4.31、1.31、0.41 dB。

整车天线无源性能测试结果计算模型研究

整车天线测试是为保障智能网联汽车通信性能而开展的基础性测试。在实际测试场景中,结果数据的处理和分析是一个重要环节。天线种类复杂、测试频点众多、计算需求多样等因素,增加了结果数据处理和分析的难度及复杂度。本文以目前最常见的球面近场测试为研究背景,以线性平均增益计算为研究目标,提取了整车天线测试场景下的关键要素,归纳了数据处理的关键环节,设计出线性平均增益计算模型的整体框架。针对不同测试场景,对结果计算模型的数据处理逻辑进行了详细的设计。该模型通过模块化、流程化的设计,在满足不同计算需求的同时能够大大提高测试结果数据处理的效率。

改进遗传算法应用于超低副瓣天线阵的综合设计

提出了一种改进的遗传算法。在同一代中对各个个体采用不重复交叉和不重复变异的策略和分别在交叉和变异后采用精英保留的策略,并改进了自适应规则。将该算法应用于实现线阵超低副瓣方向图。将各个天线单元的电流幅度和单元间距作为参量进行优化。给出了线阵天线单元在不同单元个数和不同间距条件下的优化结果。结果表明,该改进的遗传算法能够优化实现低于-40dB的超低副瓣,优于已有文献中遗传算法对天线阵副瓣的综合设计结果。

遗传算法在宽窄波束切换天线阵设计中的应用

采用对天线单元开关通断的方法,使天线阵形成不同的远场辐射方向图,实现阵列天线方向图宽波束和窄波束的切换。对一个24元线阵天线阵进行了设计。提出了一种改进的遗传算法及其目标函数模型。采用该算法对天线阵各个天线单元的电流幅度进行了优化计算,计算结果显示能够产生满足设计要求的宽波束和窄波束方向图。最后采用HFSS软件进行了仿真,计算结果与仿真结果吻合,证明了所提方法的有效性。