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.     

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.     

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.     

Mode Matching Analysis for a New Millimeter Wave Omni-Directional Antenna Consisting of Circular Rod Corrugations Gloved with a Dielectric Shell

A new millimeter-wave omnidirectional antenna consisting of circular rod corrugations gloved with a dielectric shell is investigated. As an eigenvalue problem, the antenna is analyzed with the rigorous mode matching method. The radiation characteristics of the antenna are calculated in the Ka-band frequency range. A comparison of the leaky characteristics is made between the antennas with and without dielectric shell. It is found that the circular dielectric shell layer greatly affects the leaky characteristics of the antenna and the leakage constant increases considerably. In such a way, the length of the antenna can be reduced tremendously with higher radiation efficiency. This fact indicates that the proposed leaky wave antenna is of essentially practical significance for the case where the limitation in size and weight of system is strictly required. The effectiveness and reliability of the present analysis are verified by the calculated and experimental results given in the literature.     

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.     

Dominant mode leaky-wave antenna with backfire-to-endfire scanning capability

A novel dominant mode leaky-wave antenna is proposed. This antenna is a transmission line structure with radiating wavenumber increasing from negative to positive values, providing backward to forward scanning capability as the frequency is increased. The characteristics and performances of the antenna are demonstrated by full-wave simulation and measurement results.     

基于FDTD的微带缝隙漏波天线分析

应用时域有限差分法(FDTD)对微带缝隙漏波天线进行分析,直观地得到了微带缝隙漏波天线内部的电场分布。提出了一条有效的经验公式,成功地计算了微带缝隙漏波天线的漏波传播系数,与实验数据吻合较好。比较了不同缝隙宽度和微带宽度对微带缝隙漏波天线性能的影响。证明了在微带漏波天线上开缝可以有效地减少天线尺寸及降低天线的工作频率。     

Perturbation Analysis for a New Omni-Directional Antenna Consisted of Circular Rod Corrugations Gloved with a DNG Shell

A new omni-directional leaky-wave antenna is proposed in the paper, which is consisted of circular rod corrugations gloved with a Double-negative (DNG) shell. The leaky characteristics of the new antenna are analyzed by improved perturbation method. The electromagnetic fields are described in terms of a radial transmission-line network, which tremendously simplifies the analysis procedure with good calculation accuracy and brings considerable physical insight into the overall behavior of the dielectric grating antenna. The case where the n?=??1 space harmonic of TE₀₁ mode radiating into the space is carefully investigated, it is demonstrated that the gloved cylindrical DNG shell greatly enhances the leaky strength of the antenna. As a result, the dimension of the antenna could be largely reduced keeping the radiation efficiency unchanged, which is of practical significance for some applications.     

Microstrip-fed microstrip second higher order leaky-mode antenna

With the appropriate placement of the slots and via holes, the microstrip second higher order leaky-mode antenna fed by a microstrip is presented. Two main beams with titled angles from the strip are measured in the predicted radiation leaky band. The leaky band of the microstrip second higher order mode is deduced from the characteristics of the propagation constants that are calculated by the spectral domain analysis. The proposed feeding method provides a direct connection with the circuits based on the microstrip line     

Broadside radiation from periodic leaky-wave antennas

A double-strip grating leaky-wave antenna consisting of two strips per unit cell is analyzed. The stopband behavior exhibited at broadside scan in the single-strip grating antenna is characteristic of all periodic leaky-wave antennas having a single strip per unit cell, and results in a drastic increase in the attenuation rate of the leaky wave as the beam is scanned to broadside. By nearly eliminating this stopband behavior, the double-strip leaky-wave antenna can scan from backward end fire to forward end fire without any large frequency regions of high attenuation. An approximate design rule for the double-strip antenna is discussed, and results are presented to show how the antenna may be further optimized to achieve the minimum possible variation in attenuation as the beam is scanned through broadside. Although the stopband behavior is never completely eliminated with the addition of the extra strip, the optimum design shows an almost negligible region of rapidly varying attenuation near broadside     

Brewster angle effect on the performance of omni-directional circular dielectric grating antenna-improved perturbation analysis

The radiation characteristics of the omni-directional periodic leaky wave antenna operating in TMol mode is investigated by the improved perturbation method with a particular attention directed to the Brewster angle effect on the performance of the antenna, and some interesting results are given.     

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.     

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.     

一种新型多层介质悬置微带线漏波特性的分析

提出了一种多层介质悬置微带线天线结构,以改善天线的频扫特性.分析表明:该结构不仅可以确保天线工作在效率较高的天线模工作区,而且它的泄漏常数在相当宽的范围内随频率都能平坦地变化.对频率扫描天线能保证当波束扫描时,可以保持一个相对稳定不畸变的辐射方向图.     

Evaluating near-field radiation patterns of commercial antennas

A source reconstruction technique from the measured near fields is proposed to obtain a set of equivalent currents that will characterize the forward and backward radiation patterns of an antenna. Once the equivalent sources are determined, the electromagnetic field at any aspect angle and distance from the antenna can be calculated. In this paper, the method is applied to the evaluation of the radiation from commercial antennas at any observation point. The electric field patterns of a DCS base station antenna at 1800 MHz and a horn antenna at 2500 MHz have been calculated and plotted at several distances from the antenna. This method can be used in characterizing the "reference volumes" or exclusion zones for transmitting antennas dealing with the maximum levels of electromagnetic radiation safe for human exposure, as stated in many national and international regulations.     

Analysis and design of feeding structures for microstrip leaky waveantenna

Three arrangements of the feeding structure for the excitation of a microstrip leaky wave antenna are proposed and investigated in this paper. A full-wave spectral domain integral equation method combined with the fundamental mode sampling technique is applied to determine the reflection coefficient of the excitation source. Tabulation technique is used to reduce the computational effort. Dependence on structural parameters such as line width, line spacing and overlap length is fully analyzed to obtain the design criteria for a microstrip leaky wave antenna. Additionally, an experimental setup is used to check the validity of our numerical results and verify the radiation nature of the microstrip line first higher-order mode     

Perturbation Analysis of Dielectric Grating Antenna with LHM Substrate

A dielectric grating leaky wave antenna with a substrate consisted of left handed material (LHM) is presented in this paper, the case where the n?=??1 space harmonic of TM mode radiating into the space is carefully investigated through the improved perturbation analysis, which tremendously simplifies the analysis procedure with good calculation accuracy and brings considerable physical insight into the overall behavior of the dielectric grating antenna. It has been found that the new leaky wave antenna is of larger leakage constant than that of the traditional antenna with substrate of the right handed material (RHM). 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.     

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.     

Analysis of the characteristics of NRD waveguides loaded with periodic metallic strips by using the method of lines for millimeter wave filter and antenna application

In this paper, the propagation characteristics of NRD waveguide loaded with periodic metallic strips are analyzed in terms of the method of lines. Numerical results show that such structures are most suitable for millimeter wave bandstop filter and NRD waveguide beam scanning leaky wave antenna application.