A new leaky wave antenna for millimeter waves using an asymmetric strip in groove guide, Part II: Design considerations

part I of this pair of companion papers describes a new type of leaky wave antenna for millimeter wavelengths and presents derivations of the parameters of the transverse equivalent network that accurately characterizes its leaky wave behavior. From a resonance of this transverse equivalent network, one obtains a dispersion relation in closed form from which numerical values of the leaky wave behavior have been obtained. Part II begins with this dispersion relation and a brief discussion of the numerical procedure employed. The relations between these leaky wave properties and the design of leaky wave antennas form the main concern of Part II. In this context, design aspects are discussed, including optimization considerations and the fact that they are frequency independent, and then a variety of numerical results are presented, together with their relevance to leaky wave antenna performance. It is seen that this antenna is capable of systematic design and is versatile with respect to the scan angle and beamwidth of the radiation.     

A NEW LEAKY WAVE ANTENNA BASED ON CHANNEL GUIDE FILLED WITH LEFT-HAND MATERIAL FOR MILLIMETER-WAVE APPLICATIONS

A new leaky wave antenna based on channel guide filled with left-handed material (LHM), operating in evanescent surface mode of TM polarization, is presented for millimeter wave applications. A transverse equivalent network that yields a dispersion relation in closed form is employed to analyze the leakage characteristics of the antenna. Numerical results are presented for the phase and leakage constants of the antenna in terms of different geometric parameters and dielectric distributions. Besides, the frequency dependences of the leaky characteristics for the present antenna are given, from which the backward radiation is clearly demonstrated.     

LEAKY CHARACTERISTICS OF A NEW MILLIMETER WAVE ANTENNA BASED ON GROOVE GUIDE WITH AN ASYMMETRIC CONDUCTOR STRIP

A new millimeter wave leaky wave antenna is presented in this paper, which is a modification of the groove guide with an asymmetric conductor strip by introducing a dielectric slab into the conductor plane region of the groove guide antenna. The leakage property of the new antenna is carefully examined through calculations of an equivalent network, which is developed here with taking into account the coupling between different modes to guarantee the calculating accuracy. It has been found that the new leaky wave antenna is of larger leakage constant than that for the original groove guide antenna because of the introduction of the dielectric slab. Extensive numerical results of the leakage characteristics are given to establish useful guidelines for the design of the new type groove guide leaky wave antenna.     

Guidance and Leakage Properties of a Class of Open Dielectric Waveguides: Part II--New Physical Effects

A class of open dielectric waveguides is discussed which is of direct importance to the areas of integrated optics and millimeter-wave integrated circuits. An accurate analysis of the properties of these waveguides reveals that interesting new physical phenomena, such as leakage and sharp cancellation or resonance effects, may occur under appropriate circumstances. The resulting leaky modes form a new class of such modes since the leakage, in the form of an exiting surface wave, has a polarization opposite to that which dominates in the bound portion of the leaky mode. These new effects are caused by TE-TM mode coupling, which was neglected in earlier approximate treatments. Part II describes the new physical effects and includes numerical results on various waveguiding structures to illustrate the new effects quantitatively.     

A New Leaky Waveguide for Millimeter Waves Using Nonradiative Dielectric (NRD) Waveguide-Part I: Accurate Theory

An almost-rigorous analysis is presented for a new leaky waveguide of simple configuration based on a recent nonradiative modification of H guide suitable for millimeter wavelengths, The analysis employs a transverse equivalent network that yields a dispersion relation in closed form, and contains some interesting and subtle features. Numerical values are presented for the phase and leakage constants in terms of the different geometric parameters and the dielectric constant comparisons with measurements are made in the companion paper, part II.     

基于不同等效面的漏波天线辐射特性研究

基于等效原理计算了一款分别使用线电流源与线磁流源激励的一维无限长漏波天线的总场辐射方向图和漏波辐射方向图.应用等效原理,两种辐射方向图均分别使用了等效面电流和等效面磁流两种不同的等效方法推导.使用谱域法推导出天线总场与漏波辐射场方向图的解析解并使用互易性原理推导出总场的辐射方向图以作对比.对比结果显示不同等效面得出的漏波场辐射方向图不同.     

Helix Leaky Waveguide

The propagation characteristics of leaky waves in a helix waveguide covered with a slitted cylinder are presented by a method of transverse network representation. The main interest is in helix waveguides with small pitch angles, characterized by a hybrid mode consisting of TE/sub 01/, and a small amount of TM/sub 01/ modes. The leaky wave discussed in this paper may then be regarded as a perturbation of the TM/sub 01/ wave by the slitted cylinder outside the helix. The radiation, metal, and dielectric losses are calculated numerically at a frequency of 50 GHz. The relation between the radiation loss and aperture angle of slit is very different from that of an ordinary leaky waveguide composed of a slitted cylinder without helix, especially when the distance between the helix and shield cylinder is about a quarter of the radial wavelength. The metal and dielectric losses are the same order as radiation loss, however the dielectric loss decreases as the power factor /spl epsiv/"/ /spl epsiv/' increases. The measured total attenuation constant averages about 5 dB/km, almost twice the theoretical value.     

An Improved Perturbation Analysis of a New Omnidirectional Circular Rod Antenna with Double Dielectric Gratings for Millimeterwave Application

The leakage characteristics of a new millimeter-wave omnidirectional circular rod antenna with double dielectric gratings are analyzed by an improved perturbation method. The electromagnetic fields are described in terms of a radial transmission-line network, which brings considerable physical insight into the overall behaviour of the leaky wave antenna. The analysis yields expression for the leakage constant in a closed form so that the design procedure of the antenna becomes very convenient. It is found that under the condition of the same radiation intensity, the double dielectric-grating antenna has relatively smaller dimension than that of the single one. The results obtained by the present analysis are compared with the exact solution based on the mode matching method; it is found that the improved perturbation analysis yields as accurate results as the rigorous method with extreme simplicity of the analysis and calculations.     

毫米波介质栅漏波天线的改进微扰法分析

本文用改进的微扰法分析了毫米波介质栅漏波天线的辐射特性。文中通过横向谐振法确定漏波天线的相位常数,而漏波常数的计算归结为对有源传输线方程的求解。所得数据和用场匹配方法得到的精确值进行了比较,结果表明,本文方法在保持相同精度的情况下,简化了分析和计算过程。     

Radiation of millimeter waves from NRD leaky wave antennas withtapered transition and tuning aperture

The radiation of millimeter waves from the nonradiative dielectric (NRD) leaky wave antennas with the tapered transition and the tuning aperture is investigated. An accurate theory for the leakage constant and the phase constant of the antennas is presented, which is based on the generalized scattering parameters considering the higher-order mode interactions at the discontinuities. The associated transverse equivalent network involves the characterization of the mode couplings at two air-to-dielectric interfaces, the coupled mode analysis of the tapered transition, and the calculation of the radiation fields at the tuning aperture via the extended spectral domain approach. The interesting behavior of the present modified configuration of NRD leaky wave antennas is illustrated by typical examples. The validity of the theory is confirmed by the comparison of the theoretical results with experimental data for the limiting cases     

基于Minkowski分形CRLH结构的微带漏波天线

将Minkowski分形理论应用于文献中提出的复合左右手传输线结构,使其带宽从2.78～3.30 GHz展宽到2.02～4.53 GHz.对新结构色散特性进行分析,给出色散曲线,确认其为平衡结构,并在此基础上设计了一款微带漏波天线.由于复合左右手单元结构具有左手和右手特性,漏波天线可以分别实现后向辐射和前向辐射,在平衡状态下,消除了平衡点附近的阻带效应,平衡点处的群速不为0,有行波传播,天线可产生横向辐射.仿真和测试结果表明,该文所设计的漏波天线工作频段为2.35～3.20 GHz,相对带宽为30.6％,且能实现从后向到前向连续辐射,克服了传统漏波天线后向辐射角和前向辐射角不连续的缺点.     

IMPROVED PERTURBATION ANALYSIS OF MILLIMETER-WAVE DIELEC TRIC GRATING LEAKY WAVE ANTENNA

An improved perturbation procedure is used for analyzing the radiation character-istics of the millimeter wave dielectric grating leaky wave antenna. The electromagnetic fields aredescribed in terms of an active transverse transmission line network, which brings considerablephysical insight into the overall behavior of the antenna. The analysis is simple and practical. Itsaccuracy is as high as the rigorous method.     

Guidance and Leakage Properties of a Class of Open Dielectric Waveguides: Part I--Mathematical Formulations

A class of open dielectric waveguides is discussed which is of direct importance to the areas of integrated optics and millimeter-wave integrated circuits. An accurate analysis of the properties of these waveguides reveals that interesting new physical phenomena, snch as leakage and sharp cancellation or resonance effects, may occur under appropriate circumstances. The resulting leaky modes form a new class of such modes since the leakage, in the form of an exiting surface wave, has a polarization opposite to that which dominates in the bound portion of the leaky mode. These new effects are caused by TE-TM mode coupling, which was neglected in earlier approximate treatments. Part I presents the mathematical formulation based on a rigorous mode-matching procedure.     

一种基于左手介质的新型介质栅漏波天线的理论分析

提出了一种基于左手介质的新型介质栅漏波天线,并采用多模网络与严格模匹配相结合的方法,对该左手介质栅天线的辐射特性进行了仔细严格的分析.文中给出了漏波系数随天线结构参数变化的关系以显示该左手介质天线特有的性质.数值结果表明这种新型漏波天线比传统介质栅天线具有更强的辐射能力.讨论了产生这种现象的原因.     

An asymmetric feeding X-band active frequency-scanning leaky-wave antenna

An asymmetric feeding X-band active leaky-wave antennas is developed, to excite the first high order mode of the microstrip leaky wave antenna. One is the asymmetric feeding leaky-wave antenna which integrated with a HEMT oscillator, and the other is the frequency-tuned leaky-wave antenna which integrated with a varactortuned HEMT VCO. The microstrip leaky-wave antenna is operated in the first higher mode. To excite the first higher mode, the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the center of the microstrip leaky wave antenna. The design of these active leaky-wave antennas is discussed and the beam scanning phenomena of the antenna is presented. The HEMT oscillator frequency is controlled by tuning the varactor DC bias and the beam scanning is demonstrated. The measured scanning angle agree with prediction, it is close to 30° as the VCO frequency tuned from 8.06 GHz to 9GHz.     

Leakage of the dominant mode on stripline with a small air gap

In addition to the expected bound (proper) dominant mode, an independent leaky, (improper) dominant mode has been found to exist on a conventional stripline that has a small air gap above the conducting strip. Such an air gap often occurs during the fabrication process, and has in the past been suspected as the cause of spurious performance. This newly discovered leaky dominant mode leaks into the fundamental TM ₀ parallel-plate mode of the background structure, which is a parallel-plate guide with an air gap. Furthermore, it is found that the leaky dominant mode, not the bound dominant mode, is the continuation of the stripline TEM mode that exists with no air gap. Hence, it is the leaky mode that is excited predominantly by a conventional feed for the small air-gap structure. The general properties of both the bound and leaky dominant modes are obtained by using a full-wave spectral-domain approach. The primary purposes of this paper are to discuss the nature of the leaky dominant mode, and to show that its presence is indeed responsible for spurious transmission-line performance, such as unexpected loss and crosstalk, and interference between the bound and leaky dominant modes. These conclusions are verified experimentally     

A Double-Beam Radiation Leaky Wave Antenna Based on Left-Handed Material Slab with Metallic Strips Periodically Loaded

A new leaky-wave antenna structure is carefully investigated in the paper, which is based on a grounded Left-Handed material (LHM) slab periodically loaded with metal strips. A rigorous formulation similar to the spectral domain method for planar circuits is deduced to analyze the radiation characteristics of the antenna. Theoretical analysis results reveal that at specific frequency region or with proper geometrical parameters chosen, the present structure supports simultaneously two leaky modes corresponding to the forward and backward radiations. The principle of the antenna is due to the peculiar propagation properties of the unperturbed LHM grounded slab waveguide, which is totally different from the phenomenon of double or even more space harmonic mode radiations in normal periodic structures. Extensive numerical results of the leakage characteristics are given to establish useful guidelines for the design of the new type leaky wave antenna.     

A New Dielectric Grating Antenna with Large Leakage Constant for Millimeter-Wave Applications

The leakage properties of a new dielectric grating leaky wave antenna are carefully examined by an approach of combining the multimode network theory with the mode-matching method. A systematic comparison is given for the leaky characteristics of the n?=??1 space harmonic of TM mode polarization between the present antenna and the traditional one. It has been found that the former is not only of lower conductor loss, but also of larger leakage constant than the latter. As a result, the dimension of the antenna could be largely reduced, which is of practical significance for some applications. Extensive numerical results of the radiation characteristics are given to establish useful guidelines for the design of the new grating antenna. Furthermore, special features such as cancellation or resonance effects are high-lighted and discussed. Physical insights for the mathematical findings are also presented.     

A Gunn-Diode Active Leaky-Wave Frequency Scanning Antenna

A frequency tunable active leaky-wave scanning antenna using Gunn-diode voltage control oscillator (VCO) as source is developed. The frequency tuning controlled by changing either the varactor diode dc bias or the Gunn diode dc bias is demonstrated. The measured scanning angle of active antenna is close to 15 degree as the Gunn VCO frequency tuned from 12.58GHz to 12.98GHz. To excite the first higher order mode of the microstrip leaky-wave antenna is fed asymmetrically. The dominant mode excitation has been successfully suppressed by adding a sequence of covered wire in the middle line of the microstrip leaky wave antenna. This is a prototype of frequency scanning antenna using two terminal device, which can be easily scaled up to millimeter wave frequency region.     

一种研究开导波结构中截止区辐射特性的有效方法

开导波结构中存在束缚区与辐射区,而辐射区又可划分成天线区和截止区.人们对导波在束缚区与天线区过渡的研究已经相当透彻,但是由于泄漏效应和截止效应在整个辐射区内同时存在,天线区和截止区的过渡变得异常复杂.如何合理地划分天线区和截止区成了漏波现象研究中一个重要课题.本文通过对传统截止区定义的拓广,使用复介电常数的概念,给出了一种较为简单可靠的判断准则.根据该准则我们分离出泄漏效应和截止效应各自对衰减常数的贡献,并推导出在截止区内衰减常数的解析表达式.该表达式清楚地显示了截止区中大衰减常数低辐射效率的现象.