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     

基于光子晶体的多频微带缝隙天线的设计与仿真

在普通微带缝隙天线介质基板内引入光子晶体结构,设计了一种基于PBG结构的多频微带缝隙天线,采用平面波展开法对该天线进行了理论分析,并用HFSS 10.0对该天线进行了仿真.与传统的微带缝隙天线相比,PBG结构的引入改善了微带缝隙天线的辐射特性及多频工作性能.该天线可以用于跳频通信系统中.     

Generalized Partial-Element Equivalent-Circuit Analysis for Planar Circuits With Slotted Ground

A generalized partial-element equivalent-circuit (PEEC) method is proposed for modeling a planar circuit with a thin narrow slot on the ground. The approach is based on the coupled mixed potential integral equations for a problem with mixed electric and magnetic currents. The coupled integral equations are converted into a lumped-element circuit network using Kirchhoff's voltage law and Kirchhoff's current law of the circuit theory. The full-wave Green's functions for a grounded dielectric substrate problem are used. The interactions between electric current on a microstrip line and magnetic current on a slot are taken into account by introducing two kinds of controlled sources. This generalized PEEC model will be very useful in signal-integrity analysis for multilayered circuits. To validate the generalized model, three numerical examples consisting of microstrip lines and slots on the ground are presented. The results obtained by the proposed generalized PEEC model are compared with those obtained by commercial electromagnetic simulation software and published experimental results. Good agreement is obtained.      

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     

Dual-frequency electric-magnetic-electric microstrip leaky-mode antenna of a single fan beam

This paper presents a dual-frequency electric-magnetic-electric (EME) microstrip exhibiting two leaky-wave regions of similar radiation characteristics like the microstrip EH/sub 1/ mode. The EME microstrip incorporates a photonic bandgap (PBG) structure, which is a two-dimensional array consisting of unit cell made of coupled coils connected by a via. The PBG structure employed in the EME prototype conducts at dc and shows the first stopband between 8.8-12.4 GHz, thus rendering the so-called magnetic surface. The EME microstrip is essentially made by substituting the PBG cells for the metal strip of a conventional microstrip. The finite-element method (FEM) analyses of the PBG structure show that the first and second modes are TM-like and TEM-like, respectively. The latter is leaky between 12.4-12.9 GHz and is found to be responsible for the second leaky region of the EME microstrip. The dispersion characteristics of the EME microstrip are obtained by two theoretical methods, namely, the matrix-pencil method and the FEM. Both show excellent agreement in the two leaky regions. Furthermore, the measured far-field radiation patterns of the two leaky regions also validate the dispersion curves. The first leaky region is of EH/sub 1/ type and between 5.05-5.45 GHz. The second leaky region radiates a frequency-scanning fan beam between 11.95-13.0 GHz, similar to those of the EH/sub 1/ mode. Detailed modal current analyses show even and odd symmetry along longitudinal and transverse plane of EME microstrip, respectively, further confirming the two leaky regions behave like the well-known EH/sub 1/ leaky mode. The proposed EME microstrip enriches the modal characteristics of the conventional, uniform microstrip and is thus a manifestation of application of PBG structure for new guiding device.     

A new aperture coupled microstrip slot antenna

A new aperture coupled design is proposed for microstrip slot antennas to improve their radiation performance. The proposed design is based on a new aperture coupling technique in which the slot is fed by a microstrip line and coupled to several parasitic patch radiators etched on the opposite side from the slot. In contrast to the combination of a slot and a microstrip patch in conventional aperture coupled microstrip antennas, the patches here are employed to reduce the radiation into the half-space that they occupy and increase the radiation in the other half-space. Therefore, the slot antenna can produce radiation patterns with a high front-back ratio. The above objective is achieved by optimizing standing wave distributions of the aperture electric field in the slot through the adjustment of the position of the patches along the axis of the slot. In this paper, design considerations are given, and the results are validated by numerical simulations and experimental measurements.     

New MIC Power Dividers Using Coupled Microstrip-Slot Lines: Two-Sided MIC Power Dividers

New microwave integrated circuit (MIC) power dividers have been proposed. These power dividers utilize both substrate surfaces and employ coupled microstrip-slot lines, microstrip lines, and slotlines; therefore, we make use of the two-sided MIC technique. The out-of-phase-type power dividers, as well as the in-phase-type circuits, can be constructed by the circuit configuration method described in this paper. Coupled microstrip slot lines, an important component of the power dividers, have been analyzed by the spectral-domain method, and their characteristics have been calculated and the numerical results shown for several different structural parameters for the purpose of designing power dividers. The out-of-phase-type power divider was fabricated at the 26-GHz band and good performance achieved, confirming the calculated accuracy through experimental results. The new two-sided MIC power dividers are expected to have wide applications at the millimeter-wave band.     

Single-conductor strip leaky-wave antenna

This paper presents a leaky-wave antenna with only a single-conductor strip on a substrate without a practical ground plane. The full-wave integral equation method is used to investigate the EH/sub 01/ leaky mode of this single-conductor strip structure. When this single-conductor strip is on a thin substrate with a low dielectric constant, a broad-band radiation regime can exist for the EH/sub 01/ leaky mode. The balanced microstrip lines and the inverted balanced microstrip lines are used to excite this EH/sub 01/ leaky mode. This work presents both the numerically simulated and measured data. The measured bandwidth of a voltage standing-wave ratio /spl les/2 is from 6.55- 13.75 GHz (2.34:1). In this case, the normalized phase constant is very close to 1 and this results in a fixed main-beam radiation pattern in the end-fire direction. This leaky-wave antenna with only a single rectangle stripline of length 110 mm can achieve the same broad-band performance as a tapered microstrip leaky wave antenna with a length 310 mm, as previously reported by the authors.     

A generalized method for distinguishing between radiation andsurface-wave losses in microstrip discontinuities

A generalized method for calculating both radiation and surface-wave losses is developed for microstrip discontinuities. The losses are determined by a rigorous Poynting vector analysis where the current distribution over the microstrip discontinuities is a result of a full-wave moment method solution. The power loss mechanism of such microstrip discontinuities as open-end, right-angle-bend, gap and stub lines, EMC lines, and rectangular patches are investigated. A self-consistency check of the result based on power conservation is performed to confirm the numerical results. It is found that, above a certain frequency, the surface-wave loss becomes more important than the radiation loss     

Circularly polarised microstrip antenna with a tuning stub

A simple circular polarisation (CP) design of microstrip antennas using a tuning stub is proposed and studied. It is also demonstrated that, by applying this CP design method to a circular microstrip patch with a cross slot having equal slot lengths, a compact circularly-polarised microstrip antenna can easily be implemented, with much more relaxed manufacturing tolerances as compared to the case of using a cross slot of unequal slot lengths. Details of the antenna designs are described, and experimental results are presented and discussed     

An Analysis of Gap in Microstrip Transmission Lines

Although microstrip transmission lines have been widely used in microwave integrated circuits, the discontinuity structures in the microstrip transmission lines such as a gap, an abruptly ended strip conductor, and so on, have hardly been analyzed. An analytical method and numerical results for a gap capacitance in the microstrip transmission line are described. The equivalent circuit parameters are formulated with three-dimensional Green's functions, based on a variational principle. The numerical results are in good agreement with the published experimental data. The fringing effect of an abruptly ended strip conductor is also investigated.     

一种渐变槽线作馈源的新型微带反射阵

提出了利用渐变槽线天线物理截面小的特点与变极化技术相结合的方法来改善微带反射阵馈源的遮挡效应,并设计了用于变极化微带反射阵馈源的渐变槽线天线及含37单元的微带反射阵。鉴于这些特点,该类天线在雷达、移动通信等领域具有潜在工程应用。文中给出了部分的理论分析和实例佐证。     

Reduction in Reflections and Ground Bounce for Signal Line Over Slotted Power Plane Using Differential Coupled Microstrip Lines

This paper investigates the noise reduction in the slot-induced ground bounce noise by using differential signaling. An efficient 2-D finite-difference time-domain method together with equivalent circuits for both the differential line and the slot is established and simulations are performed for a three-layer structure to characterize the ground bounce coupling. A simple model is then proposed to understand how the differential coupled microstrip lines can help reduce ground bounce. Different factors which affect noise reduction are investigated, such as the coupling coefficient, rising time, skew of differential signaling, and structure asymmetry in slotline. An experimental setup is devised to demonstrate the noise coupling between signal lines due to the slot-induced ground bounce and significant noise reduction by employing differential signaling. A favorable comparison between the simulation and measured results validates the proposed equivalent circuit model and analysis approach.      

人体中心网络微带缝隙天线设计和研究

设计了一款小型微带缝隙天线.通过电磁仿真软件CST的参数优化功能,对微带缝隙天线缝隙的长度、宽度、馈电点等参数进行优化,得到了工作频率为2.45GHz,带宽100 MHz、阻抗匹配良好、辐射效率较高的用于人体中心网络的微带缝隙小型天线,根据仿真设计,制作了天线,测试结果和仿真结果吻合较好.     

Investigation of integration paths in the spectral-domain analysis of leaky modes on printed circuit lines

The different integration paths that may arise in the spectral-domain analysis of leaky modes on open printed-circuit transmission lines such as microstrip are investigated. There are an infinite number of paths in the complex plane that may be used to construct leaky-mode solutions. Not all of the paths are valid mathematically. Among the mathematically valid ones, a certain subset correspond to paths that yield "physically valid" solutions. When tracking leaky-wave solutions as frequency changes, it is found that the propagation constants of the leaky modes may go through nonphysical "growing" regions where the attenuation constant is negative. These nonphysical regions may appear between physically valid frequency regions, implying that the leaky modes should be tracked in all frequency regions, including the nonphysical growing ones, in order to obtain the complete frequency dispersion behavior of the leaky mode. The migration of the leaky modes into these nonphysical growing regions gives rise to unconventional integration paths never seen before. Such paths must be used if the dispersion behavior of the leaky modes is to be plotted for all frequencies.     

Computation of frequency-dependent propagation characteristics ofmicrostriplike propagation structures with discontinuous layers

A general procedure based on the method of lines is presented for the full-wave analysis of propagation structures having layered substrates with step inhomogeneities in each layer. Examples of such structures include microslab lines and microstrip near a substrate edge. It is shown that with this extended method of lines technique the frequency-dependent characteristics, including the modal impedance, current distribution, and other properties of these structures, can be calculated. To illustrate the technique, typical structures such as microstrips on a finite-width dielectric slab and microstrips near a substrate edge are considered, and the effect of the proximity of the edge on the propagation characteristics of the microstrip is computed. For the case of a microstrip near a substrate edge, the numerical results obtained are compared with measured values of propagation constants, showing that the proximity effect is predicted to within 1%     

Numerical analysis of the propagation characteristics of multianglemultislot coaxial cable using moment method

In this paper, multiangle multislot coaxial cable is analyzed qualitatively and quantitatively. This is the extended result of the previous studies of the single-slot coaxial cable. The properties of this cable have been studied by many authors, especially for the surface-wave type. However, the slotted coaxial cable utilizing leaky waves has not been treated rigorously despite its wide use. In this paper, a numerical analysis of a leaky coaxial cable with a multiangle multislot configuration is performed to obtain many useful results, which are impossible to derive employing the approximate model frequently used in this area. Using the moment method, the propagation constant has been obtained for the leaky coaxial cable as a function of various parameters. Several slot configurations are considered to give insight into the properties of coupling loss and transmission loss complicated by simultaneous existence of leaky and surface waves     

Wide-band slot antennas with CPW feed lines: hybrid and log-periodic designs

In microwave and millimeter wave applications, slot antennas fed by coplanar waveguide (CPW) lines are receiving increasing attention. These antennas have several useful properties, such as a wider impedance bandwidth compared to microstrip patch antennas, and easier integration of solid-state active devices. In this paper novel CPW-fed wideband slot antennas are presented. The design procedure of CPW-fed hybrid slot antennas (HSA) having impedance bandwidths (VSWR<2) up to 57% is described. Theoretical and measured results are shown. We also describe the design procedure of a CPW-fed log-periodic slot antenna (LPSA). The impedance matching and the radiation characteristics of these structures were studied using a method of moment technique. Simulated and measured results for different dielectrics are presented.