A new class of resonant antennas

A new class of wire antennas called meander antennas is introduced as possible elements for size reduction. Efficiency is affected only by the ohmic losses in the wire, and cross polarization is negligible. An increase in the number of meander sections introduces less size reduction in return for an improved bandwidth. These antennas can be used to reduce the size of existing wire antennas such as Yagi-Uda antennas and log-periodic dipole arrays. A size reduction in the resonant length typically from 25-40% is obtained. More size reduction is obtained by decreasing the radius of the wire or increasing the separation of the folded arms     

A new class of electrically small antennas

This paper describes a new class of electrically small antennas, of which the principal advantages are the resistive input impedance, the radiation resistance transformation which may be obtained within the structure, and the variety of shapes which the antennas may take. The antennas incorporate resonant half-wave windings, and a simple transmission line theory is presented by which antenna efficiency and bandwidth may be calculated. Experimental methods and results are described for antennas in the order of 0.01 wavelength in height and 0.05 wavelength in diameter.     

Fractal antennas: a novel antenna miniaturization technique, andapplications

Fractal geometry involves a recursive generating methodology that results in contours with infinitely intricate fine structures. This geometry, which has been used to model complex objects found in nature such as clouds and coastlines, has space-filling properties that can be utilized to miniaturize antennas. These contours are able to add more electrical length in less volume. In this article, we look at miniaturizing wire and patch antennas using fractals. Fractals are profoundly intricate shapes that are easy to define. It is seen that even though the mathematical foundations call for an infinitely complex structure, the complexity that is not discernible for the particular application can be truncated. For antennas, this means that we can reap the rewards of miniaturizing an antenna using fractals without paying the price of having to manufacture an infinitely complex radiator. In fact, it is shown that the required number of generating iterations, each of which adds a layer of intricacy, is only a few. A primer on the mathematical bases of fractal geometry is also given, focusing especially on the mathematical properties that apply to the analysis of antennas. Also presented is an application of these miniaturized antennas to phased arrays. It is shown how these fractal antennas can be used in tightly packed linear arrays, resulting in phased arrays that can scan to wider angles while avoiding grating lobes     

Resonant frequency of a tunable rectangular patch antenna

The uniform transmission-line model is applied to determine the resonant frequency of a coaxial probe fed rectangular patch antenna tuned by a number of passive metallic posts suitably placed within the antenna's boundary. An approximate expression is given for the resonant frequency as a function of the post location and number, and of the other characteristic parameters of the antenna. Theoretical results are compared with available measured values.     

The omni microstrip antenna: a new small antenna

The omni microstrip antenna is a microstrip-shorted quarter-wave resonator that is wrapped around a cylinder. It is an electrically short antenna, and it can be made to radiate an omnidirectional pattern normal to the axis of the cylinder. Equations governing the design of the antenna are given along with a method of excitation. An example of a design at 41.4 MHz is given, and experimental results are reported.     

On the impedance of a class of biconical antennas

It is shown that the results derived in a series of papers by K, Fränz in general represent upper bounds rather than exact expressions for the impedance characteristics of a class of dipole antennas with biconical input regions.     

Impedance matching improvement for a class of wideband antennas

A simple and efficient technique for improving the impedance matching of a class of wideband antennas is presented. These antennas have impedance characteristics that exhibit dual (or multiple) resonance. The results obtained are in good agreement with the experimental test.     

一种新型探地雷达天线的设计仿真

结合探地雷达(GPR)的发射信号,设计了一款工作频率范围为0.7~1.2 GHz的角锥喇叭天线。对喇叭天线结构参数的设计过程进行了分析,并利用电磁仿真软件Ansoft HFSS对其行建模仿真。仿真结果表明:在喇叭天线工作频率范围内,天线的驻波比小于1.4,在中心频率955 MHz下喇叭天线的增益最大达到11 d B左右,满足实际探地雷达对天线系统的要求。该天线具有频带宽、电压驻波比低、增益高、方向性强等优点。     

Bandwidth enhancement and further size reduction of a class of miniaturized slot antennas

In this paper, new methods for further reducing the size and/or increasing the bandwidth (BW) of a class of miniaturized slot antennas are presented. This paper examines techniques such as parasitic coupling and inductive loading to achieve higher BW and further size reduction for this class of miniaturized slot antennas. The overall BW of a proposed double resonant antenna is shown to be increased by more than 94% compared with a single resonant antenna occupying the same area. The behavior of miniaturized slot antennas, loaded with series inductive elements along the radiating section is also examined. The inductive loads are constructed by two balanced short circuited slot lines placed on opposite sides of the radiating slot. These inductive loads can considerably reduce the antenna size at its resonance. Prototypes of a double resonant antenna at 850 MHz and inductively loaded miniaturized antennas at around 1 GHz are designed and tested. Finally the application of both methods in a dual band miniaturized antenna is presented. In all cases measured and simulated results show excellent agreement.     

The cross antenna: a new low-profile circularly polarized radiator

A low-profile circularly polarized medium gain antenna is presented. This traveling-wave antenna consists of a conducting wire or strip placed above a ground plane and following the contour of a cross with four or more branches and a diameter of around 1.5 wavelengths. The length of the wire is typically 5-20 wavelengths over one or more turns. The antenna is fed from a coaxial input and terminated in a load. Multiple arm configurations are also introduced. The antenna and its principles of operation are described. Computer modeling of the antenna is followed by the optimization of a few configurations for which design data and typical performances are given. Experimental results on both one- and two-turn versions agree well with predictions and confirm the practical value of this novel antenna configuration     

Analysis of a new compact microstrip antenna

A new compact microstrip antenna element is analyzed. The analysis can accurately predict the resonant frequency, input impedance, and radiation patterns. The predicted results are compared with experimental results and excellent agreement is observed. These antenna elements are more suitable in applications where limited antenna real estate is available     

一种新型金属透镜天线设计

为了获得具有高增益特性的天线,对传统透镜天线工作原理进行了分析。因为透镜天线板间电场模式与波导中电场模式类似,以此为依据通过改变金属透镜的金属平板间距和板脊高度,设计了一种新型金属透镜天线,迥异于传统金属透镜天线的凹形曲面结构。该天线金属透镜由多片长方形侧面加脊金属板组成,能够很好地调节口径面的相位分布,以此实现口径面同相分布,从而获得高增益性能。     

一种新型组合式多频带天线的设计与实现

宽频带、多频段、小型化是移动通信天线发展的必然趋势,而组合式多频段天线是小型化的有效途径,但天线之间互耦的存在是实现小型化的瓶颈.本文将宽频带天线中有效辐射体的概念引入到组合式多频带天线设计中,并首次提出了辐射透明体的概念,通过合理的设计将不同频带工作的天线有机组合而构成结构紧凑的多频带天线.文中详细介绍了该组合式多频带天线设计的新思路,并用本文提出的思想设计制作了一副应用在移动通信条件下的四频段组合天线,给出了其驻波比、方向图、增益等测试数据.测试结果表明:用本文思路设计的天线,完全满足用户要求,为该类天线的设计提供了一种新的思想.     

Design of a new cavity for a low-power tunable gyrotron

A new cavity design for a tunable gyrotron, with reduced mode conversion over a broad frequency range, is described. With most of the output power in the same mode as that in the cavity, there will be no need to adjust the position and orientation of the elements of the quasioptical antenna whenever the frequency is changed.     

A new CMOS electronically tunable current conveyor and its application to current-mode filters

In this paper, a new CMOS high-performance electronically tunable second-generation current conveyor (ECCII) is presented. The current gain of the proposed ECCII can be controlled electronically by adjusting the ratio of dc bias currents of the ECCII. The output terminal of the proposed ECCII has high impedance, which enables easy cascadability. Also, as an application, the proposed ECCII is used for realizing a universal current-mode filter. The filter realizes low-pass, bandpass, and high-pass responses simultaneously. The low-pass response is obtained at high impedance output and its gain can be independently tuned by changing the current gain of the relevant CC. SPICE simulation results using TSMC 0.35-/spl mu/m CMOS process model shows excellent performance for the proposed ECCII. The proposed circuit consumes average power of 6.6 mW using /spl plusmn/1.5-V supply voltages.     

一种新型类Vicsek分形多频天线的设计

在Vicsek结构的分形理论基础上进行了改进, 提出了一种具有良好空间填充性和自相似特性的新型类Vicsek分形天线, 并在接地板上引入缺陷地结构(Defected Ground Structure, DGS)来改善频率、抑制谐波, 得到了可以运用在无线局域网(Wireless Local Area Networks, WLAN)、全球微波互联接入(Worldwide Interoperability For Microwave Access, WiMAX)以及C波段卫星通信的四个频段.天线的谐振频率分别为2.45 GHz、3.46 GHz、5.8 GHz和7 GHz, 相应带宽为0.2 GHz(2.37~2.57 GHz)、0.49 GHz(3.2~3.69 GHz)、0.75 GHz (5.52~6.27 GHz)和0.56 GHz(6.68~7.24 GHz), 增益最高达到4.89 dB.天线的小尺寸及全向性辐射特性表明该天线能很好地满足便携式多频段移动设备的要求.     

一种新型超宽带单极子天线设计与仿真

通过单极子和高介电常数(相对介电常数为38)陶瓷介质谐振器的耦合设计了一种新型类齿状UWB单极子天线,以实现天线超宽频带的目的。采用软件HFSS进行仿真,并对天线模型参数进行优化,得到最佳设计效果。结果表明,该天线频带宽度为2.6~20.0 GHz(S11≤–10 dB),相对带宽达到了154%,满足超宽带天线要求。该天线实现小型化超宽带的同时,在整个UWB匹配频段内,具有良好的驻波比和方向图特性,较好地兼顾了各方面的性能。     

Effect of antenna gain and group delay variations on pulse-preserving capabilities of ultrawideband antennas

Pulse-preserving capabilities of ultrawideband (UWB) antennas, which are measured in terms of two parameters-the fidelity factor and the pulse width stretch ratio, are analyzed with respect to variations of the antenna gain and the group delay of the radiated field. With the degrees of the gain and the group delay variations quantified by their respective standard deviations from constant values, Monte-Carlo simulations are performed to evaluate the effect of different gain and group delay functions using randomly generated Gaussian profiles. The means and the standard variations of the two performance parameter distributions are monitored and their two-dimensional profiles are specifically obtained for UWB antennas operating in 3.1-10.6 GHz. The analysis also demonstrates the use of the fidelity factor and the pulse width stretch ratio as useful characterizing parameters for UWB antennas.     

A new integration algorithm and its application to the analysis of symmetrical Cassegrain microwave antennas

An efficient numerical algorithm for physical optics (PO) analysis of reflectors is presented. Cylindrical symmetry of the reflector is not essential but is assumed for purposes of illustration, and this leads to the use of Fourier representation in the azimuthal variable. The algorithm is based on quadratic approximation of the phase and polynomial approximation of the remaining portion of the integrand. The necessary integrals are generated recursively and they involve the Fresnel integral. Additional efficiency is achieved by means of an interpolation scheme. Therein one interpolates all but the rapidly varying edge diffraction contribution to the integral and then adds the explicitly calculated edge contribution at each far-field point. A few illustrative examples are included.