超宽带低背腔车载探地雷达收发天线的研究

本文研制了一种超宽带车载探地雷达收发天线系统,采用半椭圆形状的偶极子天线形式和电阻加载的方法展宽了天线的工作带宽,使天线末端的反射明显减小.分析了背腔高度对天线电性能的影响,在保证天线电性能的前提下,采用的背腔高度仅为22mm.设计并制作了一套天线样机,并安装在探测车上,在电波暗室中对天线的电性能进行了测试,测试结果与仿真结果吻合良好,这表明该超宽带收发天线可以满足车载探地雷达系统的需求.     

双频一体化超宽带探地雷达天线设计

针对目前探地雷达(Ground Penetrating Radar, GPR)产品单一频段工作所导致的耗时费力、效率低等缺点,文中设计实现了一种中心频率分别为400 MHz、1 000 MHz且带宽为200～1 500 MHz的双频一体化复合阵列天线,并将其应用于超宽带(Ultra-Wide Band, UWB)探地雷达系统中。阵列天线包含3个中心频率为400 MHz和6个中心频率为1 000 MHz的蝶形天线,具备双频段同时探测能力,可实现一条测线含两种不同频段的探测结果,克服了传统探地雷达不同频率的重复探测问题,增强了探地雷达系统的实用性。所提出的双频一体化探地雷达天线具有超宽带、高增益、波束窄等特点,其相对带宽为153%,整个带宽内最高实现17.6 dBi峰值增益,半功率波束宽度最窄为7.6°,为高分辨率、高效率探地雷达应用提供了一种新的天线方案。     

一种基于吸波材料的屏蔽领结天线的研究与应用

设计了一种基于吸波材料的屏蔽领结天线, 采用金属腔体提高天线的方向性, 并起到屏蔽作用.通过在腔体内部填充吸波材料, 来降低电磁波在金属腔内部的反射, 并改善天线的频率域特性和时间域信号的拖尾.通过有限元电磁仿真软件HFSS设计天线模型, 优化天线参数.实际天线的各项参数较加吸波材料和金属腔之前得到了有效改善:频率域上, 天线的中心频率有所降低, -10 dB以下带宽从原来的100 MHz提高至200 MHz; 时间域上, 脉冲信号的宽度降低, 信号拖尾得到了明显改善.实际探测证明, 在天线背部加填有吸波材料的金属屏蔽罩, 可以有效降低来自上方的干扰, 分离直达波和有用信号, 提高探测精度.     

具有屏蔽腔和吸波材料的探地雷达天线的FDTD分析

天线是探地雷达系统的关键部件之一,系统要求天线具有较好的辐射波形以及一定的隔离度.给出了一种可用于探地雷达系统的分布电阻加载的变形TEM喇叭天线,并且采用三维FDTD方法分析了屏蔽腔和吸收材料对其辐射特性的影响.计算结果表明,通过加入屏蔽腔和吸收材料,可以减小收发天线之间的直耦信号,使目标回波信号更加明显,从而提高了系统的动态范围.     

分布电阻加载平面蝶形偶极天线的辐射特性分析

天线是探地雷达系统的重要组成部分,它将直接影响整个系统的性能。平面蝶形天线是探地雷达中采用最多的天线形式之一,但标准蝶形天线辐射波形仍存在振荡且辐射特性受地面影响。本文给出了一种新型的分布电阻加载平面蝶形天线,并通过FDTD法分析了该天线位于近地表面时的辐射波形、输入阻抗和方向性等辐射特性。结果表明,与标准蝶形天线相比,该天线具有更好的时域波形和响应特性。最后,还分析了屏蔽腔和吸收材料对天线辐射波形和方向性的影响。     

毫米波段连续波雷达天线隔离度设计

收发系统间信号隔离度是连续波雷达天线设计的关键指标,它主导着连续波雷达系统的性能。针对本连续波雷达收发天线间具体的信号耦合通道,本文在收发天线间加装扼流槽,铺设微波吸波材料以及安装具有滤波功能的微波光子晶体结构等隔离措施,提高了收发天线间的隔离度。     

探地雷达中蝶形振子天线的改进

探地雷达是进行地下环境无损探测的一种有效工具,用来探测和识别地下目标,比如水管、电力线和通信线路、考古方面的保护等.然而,传统的探地雷达系统在可靠性、分辨率、探测深度等方面存在不足.因此,改善被测信号特性,设计和开发更高性能的天线就显得很有必要.本文研制了一种贴片电阻加载的蝶形振子天线,用时域有限差分方法对其进行了分析,实际应用结果表明天线具有良好的波形保真度,良好的辐射特性和屏蔽效果.可以广泛地应用于探地雷达和其它超宽带系统.     

加载辐射体异形机载天线的设计

针对常规蝶形天线存在尺寸较大的问题,结合天线宽带加载技术,提出了一种实现机载蝶形天线宽频带和小型化的思路,设计了一种工作在200～400 MHz频段,在蝶形主辐射体侧边加载小辐射体的机载天线。采用FR4介质印制板对天线辐射体以及馈电巴伦制作,同时采用金属背腔,实现天线单向辐射特性。天线仿真与测试均可以达到较好的效果,该天线具有67%的相对带宽(VSWR≤2),增益≥4 d B。     

介质埋藏平面蝶形天线的设计

采用了介质埋藏的形式将平面蝶形天线埋藏于介质中,并设计了渐变的平面微带巴伦给平面蝶形天线馈电,实现了不平衡到平衡的转换;还设计了三角形微带巴伦和微带传输线一起的结构形式,进行阻抗匹配。使用电磁仿真软件Ansoft HFSS对该天线进行了优化设计和仿真实验,与制作的实物天线性能进行对比。仿真和实测结果表明,该天线S11≤-10 dB仿真的相对带宽达到88.7%而实测的相对带宽为79.3%,具有超宽带特性;在工作频率处,仿真增益为6.9 dB,实测增益为5.8 dB。该天线满足某工程项目的需要,可作为探地雷达系统的收发天线。     

用于公路检测的超宽带横向电磁波喇叭天线

针对沥青路面层厚检测需求,设计了一种简单紧凑的超宽带横向电磁波(Transverse Electromagnetic,TEM)喇叭天线.相对于传统TEM喇叭天线的大尺寸设计,通过采用合理的指数渐变结构以及加载吸波材料,有效地减小了天线尺寸,极大地拓展了天线的阻抗带宽.仿真及测量结果表明:设计的TEM喇叭天线在0.83～12.8 GHz带宽内具有小于2的低电压驻波比,良好的辐射特性和较小的振铃,能够满足路用探地雷达系统要求.     

Modeling and investigation of a geometrically complex UWB GPR antenna using FDTD

A detailed analysis of ultrawide-band (UWB), dual-polarized, dielectric-loaded horn-fed bow-tie (HFB) antennas is carried out using the finite-difference time-domain (FDTD) method. The FDTD model includes realistic features of the antenna structure such as the feeding cables, wave launchers, dielectric loading, and resistive-film loading. Important antenna characteristics that are usually difficult to obtain via measurements can be obtained more directly from this FDTD model. Since the HFB antennas under consideration are intended for ground penetrating radar (GPR) applications, the effects of the half-space medium are also investigated. The simulated results serve to verify the performance of the HFB antenna design, and to optimize various antenna parameters.     

调频连续波雷达收发天线间隔离度的计算

调频连续波雷达(FMCWR)具有分辨率高、信号动态范围大、对周围电磁环境干扰小、抗干扰能力强等特点，得到广泛应用，特别适用于海事交通管制系统(VTS)。由于调频连续波雷达发射的是连续波，不能像脉7中式雷达那样可以采用电开关来控制天线的收发转换，而必须将发射天线和接收天线分隔开来，因此接收天线对发射天线的隔离度就成为FMCWR雷达设计的重要指标。本文根据洛伦兹互易定理，结合平面波谱法(PWS)，推导出调频连续波雷达收发天线间的隔离度公式，通过对比仿真计算结果和实测结果，达到了较好的一致，验证了计算方法的有效性。     

A deep parametric study of resistor-loaded bow-tie antennas for ground-penetrating radar applications using FDTD

Resistor-loaded bow-tie antennas are analyzed thoroughly to find out their performance on ground-penetrating radar (GPR) applications. The analysis is done with the finite-difference time-domain (FDTD) technique. The antenna is pulse driven and enclosed in a rectangular conducting cavity. The ability to detect a buried conducting sheet using two such identical antennas for transmitting and receiving is investigated. Simulations are carried out for various antenna parameters like end resistor values, flare angle, and antenna length. The gap between the two antennas and their height above the ground are also varied. Moreover, the results are obtained for different sizes, depths, and positions of the buried sheet. It is studied how the broadband impedance characteristics and better target discrimination with low clutter can be achieved by optimally selecting these antenna parameters. Also, it is shown that apart from the total parallel end resistance, the individual end resistor values and the number of resistors connected have no significant effect on the input impedance and the received signal.     

模拟分析具有表面等离子体效应的纳米光学天线及其阵列

基于时域有限差分方法,模拟分析了位于介质材料上的杆形和蝴蝶结形两种金纳米天线及杆形天线阵列.结果表明天线近场光斑直径约可以达到波长的1/11,蝴蝶结形天线的光斑强度可以比入射光场增强91倍.杆形天线阵列仍可以实现这种增强效应.蝴蝶结形天线中光场增强最高可以达到28000倍,而且局域化的光场町以耦合到天线臂上的纳米颗粒.     

FDTD analysis of resistor-loaded bow-tie antennas covered withferrite-coated conducting cavity for subsurface radar

This paper presents a full-wave analysis of a ground penetrating radar (GPR) using the finite-difference time-domain (FDTD) method. The antenna treated here consists of a resistor-loaded bow-tie antenna, which is covered with a rectangular conducting cavity of which inner walls are coated partially or fully with ferrite absorber. Some techniques are introduced into the FDTD analysis to obtain the accurate results and to save the computer resources. The validity of the FDTD analysis is confirmed experimentally. Furthermore, the effects of the ferrite absorber on the GPR characteristics are theoretically investigated in detail. The FDTD results indicate that the remarkable improvement of the antenna characteristics for the GPR system cannot be attained by the ferrite absorber     

Coplanar waveguide-fed uniplanar bow-tie antenna

The design of coplanar waveguide (CPW)-fed bow-tie antenna for the 2.4-GHz ISM band is described. A coplanar waveguide-to-coplanar strips (CPW-to-CPS) balun is used to obtain the balanced feed line for the printed bow-tie. An analysis method based on the mixed potential integral equation method is used to characterize the input characteristics of the bow-tie antenna. The numerical results obtained are in good agreement with the experimental data. Through experiments with bow-tie antennas of various extended angles, the bow-tie antenna with a 90° extended angle exhibits the widest bandwidth in the desired frequency band which has a bandwidth of 17% for a VSWR <1.5:1     

一种新型探地天线的优化设计

设计了一种新型超宽带平面天线.用FDTD研究了近地面天线的模拟计算问题,给出了天线的近场辐射性能.通过与平面蝶形偶极天线对比,结果表明该天线具有波形保真度好,对称的辐射方向图及后向辐射小等特点,进一步通过加载集中电阻优化设计,改善了天线的驻波特性.此天线不仅适用于探地雷达,还可以广泛地用于宽带通信和冲激雷达等系统.     

Bow-tie antennas on high dielectric substrates for MMIC and OEICapplications at millimetre-wave frequencies

A two-element bow-tie dipole antenna and a single-element bow-tie slot antenna fabricated on a high dielectric constant (ε_r=10.2) substrate are introduced for applications at millimetre-wave frequencies. The former antenna provides 2 GHz bandwidth at 35 GHz and the latter 1.3 GHz at 32.7 GHz. With a broadband match, these antennas would yield significantly higher bandwidths     

Analysis and design of broadside-coupled striplines-fed bow-tieantennas

The design of a bow-tie antenna fed by broadside-coupled striplines (BCS) for the 2.4-GHz ISM band is described. The two fins of the bow tie are, respectively, on the two sides of the substrate. The feeding balanced lines adopted are the BCS. A quarter-wave transformer is used to transform the microstrip line input to the BCS feed. An analysis method based on the mixed-potential integral equation method is used to characterize the input characteristics of the bow-tie antenna. The numerical results obtained are in good agreement with the experimental data. Through experiments with bow-tie antennas of various extended angles, the bow-tie antenna with a 90° extended angle exhibits the widest bandwidth in the desired frequency band, which has a bandwidth of 19% for a VSWR<1.5:1