A low-cost invasive microwave ablation antenna with a directional heating pattern

Microwave ablation(MWA) is a cancer treatment method. The tumor tissue absorbs electromagnetic energy, which heats and kills it. A microwave ablation antenna plays a critical role in this process. Its radiation field must completely cover the tumor but not the healthy tissue. At present, the radiation pattern of most invasive ablation antennas is spherical.However, in the clinic, the shape of some tumors may be asymmetrical or the antenna cannot be inserted into the center of the tumor for some other reason. In order to solve these problems, a directional heating antenna for microwave ablation is proposed in this paper. The proposed antenna, operating at 2.45 GHz, consists of a monopole and a reflector. The feed is given by a substrate integrated coaxial line(SICL) and coplanar waveguide(CPW). The omnidirectional radiation field of the monopole is reflected by a reflector that is extended from the outer conductors of the SICL to form a directional radiation field. The impedance matching network is designed on SICL to match the antenna to 50 Ω. The antenna is fabricated using a mature printed circuit board(PCB). The reflection coefficient of the antenna in porcine liver tissue measured by a vector network analyzer shows good agreement with the simulations. Then, an ablation experiment in porcine liver is conducted with power of 10 W for 10 min, and the experimental results confirm the validity of the design.

Analysis of the radiation Resistance and Gain of Full-Wave Dipole Antenna for Different Feeding Design

This paper demonstrates the analysis of antenna pattern and gain for different designs of full-wave dipole antenna feeding techniques. Seven such techniques were studied and analyzed;symmetrical dual feeding in phase, symmetrical dual feeding out of phase, asymmetrical dual feeding in phase, asymmetrical dual feeding out of phase, symmetrical triple feeding in phase and symmetrical triple feeding out of phase. Symmetrical dual feeding in phase produced high gain as compared to the single and center-fed antennas. An improvement of about 3 to 3.5 dB was achieved comparing to center tap fed and off center fed. It was found that an asymmetrical dual feeding in-phase provides good performance, considering the directivity, pattern, and input impedance. A 2.46 dB gain has been attained. It was found that a symmetrical triple feeding provides an overall best performance with respect to gain, radiation pattern, beam width and input impedance.

Design of a High-Gain 2 × 1 Array Antenna for S-Band Applications

Antennas are an indispensable element in wireless networks. For long-distance wireless communication, antenna gains need to be very strong (highly directive) because the signal from the antenna loses a lot of strength as it travels over long distances. This is true in the military with missile, radar, and satellite systems, etc. Antenna arrays are commonly employed to focus electromagnetic waves in a certain direction that cannot be achieved perfectly with a single-element antenna. The goal of this study is to design a rectangular microstrip high-gain 2 × 1 array antenna using ADS Momentum. This microstrip patch array design makes use of the RT-DUROID 5880 as a substrate with a dielectric constant of 2.2, substrate height of 1.588 mm, and tangent loss of 0.001. To achieve efficient gain and return loss characteristics for the proposed array antenna, RT-Duroid is a good choice of dielectric material. The designed array antenna is made up of two rectangular patches, which have a resonance frequency of 3.3 GHz. These rectangular patches are excited by microstrip feed lines with 13 mm lengths and 4.8 mm widths. The impedance of the patches is perfectly matched by these transmission lines, which helps to get better antenna characteristics. At a resonance frequency of 3.3 GHz, the suggested antenna array has a directivity of 10.50 dB and a maximum gain of 9.90 dB in the S-band. The S parameters, 3D radiation pattern, directivity, gain, and efficiency of the constructed array antenna are all available in ADS Momentum.

Mathematical Simulating Model of Phased-Array Antenna in Multifunction Array Radar

A mathematical simulating model of phased-array antenna in multifunction array radar has been approached in this paper, including the mathematical simulating model of plane phased-array pattern, the mathematical simulating model of directionality factor, the mathematical simulating model of array factor, the mathematical simulating model of array element factor and the mathematical simulating model of beam steering.

Comparative Analysis on Antenna Balun and Feeding Techniques of Step Constant Tapered Slot Antenna

This paper represents the performance analysis of the different shapes of antenna balun and feeding techniques for step constant tapered slot antenna. This work also addresses the benefits of antenna balun (circular and rectangular) along with two types of feeding techniques (Microstrip line L-shape and Microstrip line I-shape). The performance of the antenna for each technique is thoroughly investigated using Computer Simulation Technology (CST) Microwave Studio software simulation under the resonant frequency of 5.9 GHz. Results demonstrate that the proposed model is an effective tool for improving antenna performance. Moreover, an extensive comparison has been carried out between the two different shapes, with and without antenna balun and between two feeding techniques focusing on return losses, gain, directivity, and voltage standing wave ratio (VSWR).

Multi-Band Antenna with Three Folded Monopoles for Mobile Communication Systems

This paper presents the design and the experimental characterization of a new multi-band antenna consisting of three folded monopoles dedicated to mobile communication systems. The originality of this paper is to get the PMR (Professional or Private Mobile Radio) band with the GSM (Global System for Mobile Communications), DCS (Digital Cellular System) and UMTS (Universal Mobile Telecommunications System) bands. The main lobe of the antenna radiates in the zenith direction with a linear polarization over all bands. It is interesting to design the proposed antenna in order to obtain better performances in terms of directive radiation pattern (especially in the PMR band) in comparison with the already existing antenna systems in the wireless market for similar purposes. The prototype was studied with the software CST-MWS (Micro wave studio 2012). The antenna has been designed and successfully measured.

A 4-element Rectangular Microstrip Patch Antenna Array

Patch antennas are small in size and suitable for microwave transmission,so they are widely used in small portable wireless devices.Multiple patch antennas are connected together to form an array antenna.Compared with the patch antenna,the array antenna has a higher directivity gain and can achieve better transmission performance.In this project,I will test the single patch antenna first,and then move to 2×1 antenna array.Finally,built a 2×2 antenna array,test and record their performance respectively.

A Compact Diversity Antenna for Handheld Terminals

The handheld terminals antenna should have a small size, sufficient gain and big bandwidth. In this paper, a compact planar inverted-L diversity antenna for handheld terminals is proposed. Three diversity antennas operating at 2.15 GHz are designed and the effect of important parameters of the proposed antenna is measured. The isolation is found to be better than 13 dB, the usable bandwidth is about 13%. Moreover, the measured radiation patterns are also obtained that the backward radiation is decreased.

Directions of Arrival Optimization Method for Broadband Antenna Array Based on Filter Bank

This paper proposes an estimation method of the directions of arrival(DOA) for the broadband signals received by a uniform planar antenna array including the mutual coupling effect. The process modeling of antenna array receiving dynamic signal is obtained accurately via building the array system electromagnetic space-time model, and the mutual coupling effect is included in the synthesis procedure automatically. The broadband signal is divided into several sub-bands, and the complex weight of these sub-bands frequencies is figured out using the least mean square iteration programming. In the proposed method, the mutual coupling effect is compensated at the different frequencies. The calculation results show that the method is suitable for the uniform linear and uniform circular array pattern integration, and it is commendably satisfied with the requirement of engineering design.

Comparison of Circular Sector and Rectangular Patch Antenna Arrays in C-Band

The circular sector patch antenna is studied in C-band (4 GHz - 8 GHz). In this paper, we present steps of designing the circular sector antenna then a comparison with a rectangular antenna in literature. High Frequency Structure Simulator (HFSS) software is used to compute the gain, axial ratio, radiation pattern, and return loss S11 of proposed antenna. Based on the designed patch antenna, many phased arrays will be simulated using HFSS. The impact of distance between element, number of element and phase will be checked. Obtained results are analyzed and compared with literature.

机载天线方向图测试的试飞方法分析

鉴于通过天线方向图能够直观清晰地衡量机载天线的辐射特性,且基于试飞的测试方法所得方向图更能反映天线在实装环境下的性能,提出了一种基于圆航线试飞的天线方向图测试方法。对圆航线和“梅花瓣”航线下机载天线方向图的测试情况进行了对比分析;介绍了圆航线下天线方向图测试数据的预处理方法,即场强折算和方向角折算方法。测试结果表明:基于圆航线试飞的天线方向图测试方法效率较高,所得方向图的方向性能优良,在作战运用中具有较强的指导作用。

星载高增益宽频带高指向性阵列天线设计

针对卫星对X波段通信系统电磁波传输的需求,设计了一款新型X波段高增益宽频带高指向性微带阵列天线。采用平面多层板形式,通过多种技术手段改善天线性能。阵列天线采用侧馈的能量输入方式、多层缝隙耦合馈电设计提高天线带宽,同时将辐射层和馈电网络层分离以减小电磁波串扰和提升分离设计简约度,增加金属反射层以提高天线正向增益和前后比。根据工程总体需求,共设计了64阵元和256阵元的矩形微带阵列天线。两种天线经加工测试结果与仿真结果基本一致。该天线实现了高增益、宽频带、高指向性等性能指标,对X波段星地无线通信系统的设计有一定指导意义。

短波天线性能无人机测试系统研制与应用

短波天线的尺寸大,天线方向图和增益测量困难。研制的短波天线性能无人机测试系统,利用无人机搭载三轴全向选频式场强仪,在天线远场区,无人机按照规划航线水平或垂直环绕被测天线飞行,自动采集频率、场强,并与经纬度、高程聚合为数据记录,经计算和校准修正后得到天线的方向图和增益等关键性能。系统测量频率范围2~30 MHz,测量灵敏度1 mV/m,各向同性≤1 dB,频率响应≤1 dB;测量比对表明:系统测量电场精度达到±1.5 dB。实测了偶极子天线、单极天线的方向图和增益,经对比,实测与仿真的结果一致性很好,无人机测试系统具有较高的测试精度。

基于稀疏空间采样的雷达阵列天线主波束指向估计

天线主波束指向代表了雷达的能量集中方向,其在电子对抗领域是一个十分重要的信息。当已知雷达天线的主波束指向时,可以避开目标雷达的探测或对其实施精准的电子干扰。基于雷达周围部署的少量观测点,构建噪声环境下的稀疏空间采样数学模型,并提出四种雷达阵列天线主波束指向的估计算法。蒙特卡洛仿真测试结果展示了所提算法在不同条件下的估计准确性。

相控阵天线碗状变形对其辐射性能的影响分析

如何快速而准确地评估天线阵面结构变形对电性能的影响是工程上亟需解决的关键问题。文中根据某大型相控阵天线设计了3种规格的阵列天线,按照典型的天线阵面碗状变形,分别采用HFSS数值计算方法和有源阵元方向图(Active Element Pattern, AEP)计算方法计算阵元Z向误差和指向误差对电性能的影响。结果表明:当Z向偏差小于λ/20(λ为波长)时,碗状变形对副瓣电平和波束宽度的影响显著,对增益影响较小;当Z向偏差增大到λ/20时,天线增益明显恶化;随着阵元规模的增大,得益于阵元互耦效应,碗状变形对电性能的影响减弱。AEP计算方法忽略了阵元方向图的差异性及互耦效应,导致其计算精度不如HFSS数值计算方法的计算精度高,特别是副瓣计算结果差异明显。该研究可为相控阵天线结构设计参数的确定提供指导。

GPS信号载噪比研究

介绍了GPS接收机所接收信号的载噪比;提出了载噪比方向图的概念,导出了载噪比方向图与天线增益方向图的关系;初步评估了大气损耗的时空差异;指出可利用载噪比异常方向图确定被动式干扰源的方位。

大型天线罩小损耗测量的一种新方法

本文提出了大型整体天线罩小损耗测量的一种新方法,详细讨论了其测量原理和方法程序。给出了某天气雷达工程S波段8.54米天线12米罩子的传输损耗测量结果,测试结果良好。

一种对任意线阵天线的主波束赋形方法

基于自适应天线阵理论 ,给出了一种用于任意线阵天线的主波束赋形算法。该方法通过迭代获得一组最优权值 ,用来减小加权赋形方向图和期望方向图在主波束上的差别 ,同时将旁瓣电平降低到期望值。一些算例充分说明了这种算法的有效性。该算法可以有效的控制主波束方向、宽度。

相控阵天线方向图的建模与实时仿真方法

在雷达系统的优化设计的研究中,根据天线波束在扫描过程中增益、波束形状和副瓣电平等参量的特性及其变化规律,研究了相控阵雷达天线方向图的建模与实时仿真问题。为了提高相阵天线的性能,提出了一种相控阵天线方向图的实时仿真方法。并以矩形/圆形平面相控阵天线为例,采用辛格函数的变形组合给出了一种实用的相控阵天线方向图实时仿真模型。仿真结果表明方法极大地降低了仿真计算量,在保证仿真系统可信度的前提下,能够满足系统实时性的要求,模型已在某半实物相控阵雷达仿真系统得以验证。

天线方向图自动测试系统

本文介绍应用惠普VEE软件可视化编程平台,实现对频谱仪和通信链路开关矩阵远程控制,记录频谱仪扫描的天线发射方向图发射电平值,并将其输出到微软Office Excel表格中,利用编制好的VBA程序处理数据,画出所需的方向图,并制定出天线增益、3dB宽度、10dB宽度等参数的报表。测试系统提供两种频谱仪操作方式选择,提高工作效率;生成的方向图曲线进行了正反极化通道差修正。软件完成每一步测试后,交出频谱仪和通道使用权,若继续测试则按下一步要求配置系统参数。该系统使用方便,具有较高的应用价值。