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.

LOW PROFILE MEANDER LINE PRINTED QUADRIFILAR HELIX ANTENNA

In this paper,a new approach of meander line technique for Printed Quadrifilar Helix Antenna(PQHA) is studied.Compared with other meander line techniques,this approach has lowered the axial height of antenna greatly and improved the efficiency of model-building in simulation processing.We have focused on the analysis of radiation pattern,axial ratio,and design graph for the Meander line Printed Quadrifilar Helix Antenna(MPQHA).Finally,we have reduced successfully 67% size in geometry compared with traditional PQHA method,and obtained rather reasonable results.

An Inductor Model for Analyzing the Performance of Printed Meander Line Antennas in Smart Structures

Meander line antenna has been considered desirable on flight vehicles to reduce drag and minimize aerodynamic disturbance;however, the antenna design and performance analysis have made mostly by trial-and-error. An inductor model by simulating the meander line sections as electrical inductors and the interconnecting radiation elements as a quasi-monopole antenna is developed to analyze the antenna performance. Experimental verifications of the printed meander line antennas embedded in composite laminated substrates show that the inductor model is effective to design and analyze. Of the 4 antennas tested, the discrepancy of resonant frequency in simulation and experiment is within 4.6%.

Antenna-in-package system integrated with meander line antenna based on LTCC technology

We present an antenna-in-package system integrated with a meander line antenna based on low temperature co-fired ceramic(LTCC) technology. The proposed system employs a meander line patch antenna, a packaging layer, and a laminated multi-chip module(MCM) for integration of integrated circuit(IC) bare chips.A microstrip feed line is used to reduce the interaction between patch and package. To decrease electromagnetic coupling, a via hole structure is designed and analyzed. The meander line antenna achieved a bandwidth of 220 MHz with the center frequency at 2.4 GHz, a maximum gain of 2.2 d B, and a radiation efficiency about 90% over its operational frequency. The whole system, with a small size of 20.2 mm×6.1 mm×2.6 mm, can be easily realized by a standard LTCC process. This antenna-in-package system integrated with a meander line antenna was fabricated and the experimental results agreed with simulations well.

Study on a W-band modified V-shaped microstrip meander-line traveling-wave tube

The study on a miniaturized, low-voltage, wide-bandwidth, high-efficiency modified V-shaped microstrip meander-line slow-wave structure is presented. This structure is evolved from the original U-shaped microstrip meander-line slow-wave structure, combining the advantages of a traditional microstrip and a rectangular helix. In this paper, simulations of the electromagnetic characteristics and the beam-wave interaction of this structure are carried out. Our study shows that when the design voltage and the current of a sheet electron beam are set to be 4700 V and 100 mA, respectively, this miniature millimeter-wave power amplifier is capable of delivering 160-W output power with a corresponding gain of 37.3 dB and a maximum interaction efficiency of 34% at 97 GHz.

动态风向对风力机尾流演化规律的影响

为了研究动态风向对水平轴风力机尾流演化规律的影响,文中基于OpenFOAM软件平台,采用大涡模拟(LES)耦合致动线模型(ALM)的方法,分析动态风向幅值变化对尾流速度特性、湍流特性以及蜿蜒特性的影响.研究结果表明:随着动态角度幅值的变化,尾流速度上的差异主要体现在4D(D为风轮直径)以后,且随着角度幅值的增加,尾流平均速度的恢复越来越快;动态风向条件下,叶尖涡出现振荡现象,且随着动态风向角幅值的增加,振荡幅度越来越大;风向角的动态变化加剧了尾流的蜿蜒,随着角度幅值的增加,尾流中心最大偏移量增加,增长符合二次幂函数规律,且远尾流的增长率远大于近尾流;当动态角度变化幅值达到15°时,10D处的尾流中心偏移量达到了48.62%;动态风向角变化幅值的增加会改变尾流边界,导致尾流影响范围扩大.

小型化星载Ku频段宽带扇形波束圆极化天线

为适应星载天线小型化、宽带、高性能的发展趋势,提出一种小型化星载Ku频段宽带扇形波束圆极化天线。通过在H面扇形喇叭口处加入曲折线圆极化器实现天线圆极化,将传统平面圆极化器变为半圆柱形,天线的包络尺寸减小近36%。同时,在喇叭口处增加介质透镜,在有限尺寸内将球面波调节为平面波。半圆柱极化器和介质透镜的设计可共同调节入射波束角度,提升天线的宽角波束覆盖性能。利用CST软件建立模型进行仿真,仿真结果表明:天线结构紧凑、波束覆盖范围宽,俯仰面大于11.3 dBi的增益覆盖范围达90°。半圆柱极化器的设计为星载天线的小型化、低成本设计提供新的思路。

平面超材料对曲折线慢波结构行波管效率改善和杂模抑制的影响

针对U型曲折线慢波结构带状注行波管杂模抑制和互作用效率提高等面临的挑战,提出了一种开口菱形超材料结构。在综合考虑电路单元谐振性能、与U型曲折线慢波结构之间的协调配合以及电路实现可行性和结构简单等因素,通过电路设计和数值模拟优化等具体措施相结合,探讨这种超材料对增强注波互作用表面电场和抑制电路振荡的效果。在Ka波段优化的结果表明,这种超材料在抑制杂波和改善注波互作用效率方面效果明显,对此类行波管稳定性提高具有重要意义。

小型化准八木天线的仿真与实验研究

微带准八木天线具有端射的辐射方向图,设计方便,结构简单,其小型化是应用中面临的重要任务。文中针对S波段微带准八木天线的小型化技术开展了仿真和实验研究。首先,研究了基本型的印刷八木天线,在有源振子长度为50 mm和4个引向器的条件下,仿真得到驻波比小于2的频率为2.73 GHz,增益约为4 dBi;然后,在相同的有源振子横向尺寸和引向器个数条件下,采用振子曲折线技术,仿真得到驻波比小于2的频率为2.675 GHz,增益也约为4 dBi;最后,针对相同横向尺寸和引向器个数的曲折线振子,引入介质埋藏技术,对于不同厚度的高介电常数的介质基板覆盖,仿真了准八木天线的端口驻波比和辐射性能的变化情况,在介质基板的相对介电常数为9.8和厚度为8 mm的情况下,仿真得到驻波比小于2的频率为2.2 GHz,增益也约为5 dBi,方向图形状略有变化,对介质埋藏的曲折线振子八木天线进行了加工和测试,测试结果和仿真结果接近。研究结果表明,采用介质埋藏和振子曲折线技术均可以一定程度上缩减准八木天线的横向尺寸,其中介质埋藏技术效果更为明显,二者之间的结合是小型化准八木天线的有效方案,文中的研究为实际工程应用提供了技术参考。

曲折线圈型电磁超声表面波换能器的优化设计

电磁超声表面波换能器的换能效率较低,严重限制了其进一步的发展。为此,在建立曲折线圈型电磁超声表面波换能器多物理场有限元模型的基础上,通过仿真分析,分别从EMAT(Electromagnetic Acoustic Transducer)磁铁尺寸和线圈中导线的分布方式两个角度对电磁超声表面波换能器进行了优化。实验表明,与传统的曲折线圈型电磁超声表面波换能器相比,采用相同的磁铁体积时,在一发一收的工作模式下,文中提出的优化后的换能器接收信号幅度可提高39%;在收发一体的工作模式下,信号幅度可提高86.2%,有效地改善了换能器的性能。

弯折线偶极子天线谐振特性的研究

本文研究了由矩形弯折线构成的偶极子天线的谐振特性,分析了弯折线偶极子天线的弯折次数、矩形弯折的高度以及弯折角度等参数对天线谐振特性的影响。结果表明,弯折线偶极子天线的参数改变对天线谐振特性有较强的调节作用,适当的改变天线的参数可以获得较好的天线尺寸缩减特性,适合RFID标签天线的应用。

140GHz菱形微带曲折线慢波结构行波管的模拟计算

提出了一种新型的菱形微带曲折线慢波结构。该结构可适用于低电压、宽带宽、中等功率水平的高效率毫米波行波管。和传统的慢波结构相比,微带曲折线是一种平面结构,因此其加工工艺可采用2维微细加工技术。该结构可以用带状电子束进行注-波互作用,并且不需要额外的电子束通道。给出了菱形微带曲折线慢波结构在140 GHz的色散曲线和注-波互作用模拟分析。研究结果显示：在输入功率为40 mW,带状电子束的电流和工作电压分别为90 mA和7 kV的条件下,该微带曲折线行波管可以获得数十W功率输出,互作用效率可达14.3%,瞬时3 dB带宽为18 GHz（132~150 GHz）。

弯折线天线原理、结构及其研究进展

弯折线技术作为一种减小天线尺寸和实现宽频带的有效手段,在现代天线设计中被广泛使用。根据不同的技术要求,研究者们提出了多种改进结构。文中介绍了6种具有代表性的弯折线天线结构,其中包括双弯折线天线、折叠式弯折线天线、立体式弯折线天线、渐变式弯折线天线、行波弯折线天线和弯折线缝隙天线。同时也对上述6种天线的工作原理以及研究进展进行了简要的阐述。

一种用于移动终端的新型内置五频芯片天线

研制了一种用于GSM850/GSM900/DCS1800/PCS1900/UMTS频段的五频内置芯片天线.芯片天线将FR-4介质（介电常数为4.4）上的曲折线和螺旋线相结合,两者分别产生谐振频段进行叠加从而实现天线宽频工作特性.弯曲的折线结构实现了天线尺寸的小型化,天线的体积为20 mm×8 mm×3.2 mm,适合用作移动手机终端的内置天线.电路板的尺寸为40 mm×93 mm,适用于新款小型手机.在驻波比小于3时,测试低频带宽为146 MHz（1030-1176 MHz）,高频工作带宽为530 MHz（1756-2286 MHz）.

基于曲折线单元的小型化频率选择表面

为了得到小型化的频率选择表面进而避免栅瓣问题,提出了一种新型小型化频率选择表面,通过在方环单元的内部空间中增加曲折线长度来增加谐振长度。仿真计算和实验结果表明:在4 GHz谐振频率下,该小型化频率选择表面(FSS)比传统方环面积减小88%左右,而且该FSS单元具有良好的角度稳定性。

800V行波管研究

提出了一种角度对数周期微带曲折线慢波结构,该结构具有微带型慢波结构尺寸小、易加工的特点,同时特殊的结构使得它可以工作在极低的电压下,可用于低工作电压、宽频带毫米波径向束行波管。给出了这种慢波结构在Ka波段的色散特性和传输特性,并进行了注波互作用的分析。计算结果表明:该新型慢波结构的工作电压可低至809V,输出功率26W,3dB带宽约为19GHz(27～46GHz),虽然单个角度对数周期微带曲折线慢波结构的输出功率较小,但是这种结构通过功率合成,可以达到数百W的功率输出。

周期性缺陷接地结构的微带线

基于单元缺陷接地结构(DGS)等效电路模型,研究了周期性缺陷接地结构微带线的色散关系,并给出其阻带的快速估算方法。为提高微波电路的集成度和灵活性,提出了基于周期性DGS结构弯折型微带线,分析其带阻特性、色散特性和阻抗特性。实验证明,该结构在4～7GHz之间具有良好的宽阻带特性。

偶极子RFID标签天线研究

偶极子天线是RFID标签天线中应用最广泛的一类天线结构,对半波偶极子及弯折偶极子RFID标签天线进行了分析和仿真,并比较了弯折偶极子天线的形状参数对其性能的影响。仿真结果表明,在保持天线效率的前提下,与半波偶极子相比,弯折偶极子天线具有更好的尺寸缩减特性。

Ka频段回折线型宽带圆极化器设计

提出了一种可应用于Ka频段毫米波卫星通信系统的新型圆极化天线实现方案。利用回折线周期结构特性,只需在已有线极化喇叭天线的前方放置回折线型圆极化器,不需对已有线极化天线做任何内部修改,即可实现线极化向圆极化的转换。这种实现方式具有低成本、低设计复杂度、高灵活性的特点,可与现有的线极化毫米波天线无缝兼容。采用CST软件建立系统仿真模型,对回折线结构进行了参数分析,并对天线进行了加工与实际测试。实验结果表明:该天线的3dB以下轴比圆极化工作带宽覆盖27.5-32.5GHz。

轮胎嵌入式小型化UHF RFID电子标签弯折天线设计

为提高轮胎嵌入式UHF RFID电子标签读取可靠性,需要解决一对矛盾,即一方面,为保证电子标签与轮胎有良好的粘合性和绑定性,要求标签天线尺寸足够小;另一方面,轮胎无线电环境差,轮胎材料对电磁波的固有介质损耗和干扰要求电子标签天线尺寸应足够大,以提高电磁辐射能力。针对以往设计方法复杂、不利于标签与轮胎绑定的问题,根据Bode-Fano阻抗匹配的约束,利用弯折天线的周期性和紧凑性,提出了一种简单、具有良好阻抗特性和绑定特性的轮胎嵌入式小型化UHF RFID弯折天线方法,设计了一种物理空间受限的轮胎嵌入式小型化UHF RFID弯折天线。HFSS仿真验证表明,设计的天线在833~971MHz频带范围内回波损耗小于-10dB,覆盖了美国RFID标准带宽902~928MHz,最大辐射增益为2.4dBi。最后,通过设计的轮胎嵌入式RFID电子标签测试,结果表明:当读取距离小于90cm时,标签识别率大都大于80%;当读取距离小于50cm时,标签识别率大于90%,标签与轮胎具有良好的绑定效果,满足设计要求。