Excitation of Waveguide by Stripline- and Microstrip-Line-Fed Slots

This paper presents investigations on coupling between stripline/microstrip line and a rectangular waveguide coupled through a slot in the ground plane which is fixed in the cross-sectional plane of the waveguide. A closed-form expression for the impedance loading on stripline/microstrip line is evaluated from knowledge of the complex power flowing down the rectangular waveguide supporting the dominant mode and discontinuity in the modal voltage in stripline/microstrip line. The reactance cancellation is obtained by terminating the stripline/microstrip tine exciting the slot in a short-circuited stub. The structure under this condition forms a transition between stripline/microstrip line and a waveguide. The design curves on slot length versus frequency are presented for different values of dielectric constants. The variation of coupling as a function of frequency and also the location of the slot is evaluated. Numerical results for slot coupling useful for the design of waveguide simulators are also presented.     

基于T型谐振器的抗干扰矩形波导缝隙阵列天线设计

介绍了一种抗干扰矩形波导缝隙阵列天线的设计方法,仿真、设计并加工了一款基于T型谐振器的四缝隙矩形波导缝隙阵列天线. 通过在矩形波导下壁引入周期性的T型谐振器,有效提升了天线的抗干扰能力. 测试结果表明,该天线的?10 dB阻抗带宽为10.3%（5.5～6.1 GHz）,增益为11.5～12.8 dBi,天线效率为72.1%～87.3%。与传统矩形波导缝隙阵列天线相比较,本文设计天线在抑制频段 7.9～9.6 GHz的抗干扰能力提升了32.2～69.3 dB,适用于多频段、多任务的无线通信、雷达系统等.     

Rectangular Waveguides with Impedance Walls

The propagation of guided waves in a rectangular geometry having impedance boundary conditions is investigated. An impedance compatibility relation is derived that must be satisfied in order that a separable modal solution exists for a given impedance configuration. Several new rectangular waveguides are developed; among them are 1) a tall rectangular waveguide operating in a dominant H/sub 10/ mode with no H/sub 0N/ modes; 2) a rectangular waveguide with two parallel anisotropic impedance surfaces; 3) a rectangular waveguide with two parallel walls having isotropic impedance surfaces, the other two walls being anisotropic; 4) a rectangular waveguide supporting only E modes; and 5) rectangular coaxial systems containing impedance surfaces. The modal structure of rectangular waveguides with impedance boundary conditions offers advantages over the conventional waveguide. The potential of oversizing for low-loss and high-power applications is enhanced because of the additional modal control provided by the impedance surfaces. Other applications are suggested.     

一种计算波导耦合缝隙有源阻抗的方法

 针对耦合波导缝隙馈电时波导内电磁场复杂且不利于工程应用的问题,提出一种耦合波导缝隙有源阻抗计算方法.根据耦合波导端口处S矩阵与端口处输入阻抗矩阵的关系建立关于耦合波导缝隙有源阻抗方程,且采用牛顿法求解此非线性高阶分式方程,得到计及缝隙间互耦的耦合波导缝隙有源阻抗值.通过提取HFSS软件中耦合缝隙馈电的裂缝天线S矩阵进行仿真计算,结果表明该计算耦合缝隙有源阻抗的方法是有效的且适合大型裂缝天线耦合裂缝设计.     

Integral equation analysis of a sheet impedance coated window slotantenna

Presents an integral equation and method of moments analysis of a window slot antenna. The antenna is modeled by a sheet admittance coated rectangular aperture in an infinite ground plane. It is shown that the sheet admittance coated aperture is complementary to a sheet impedance plate, which permits the window slot antenna to be analyzed with existing computer programs. Numerical results are compared with measurements for input impedance and radiation efficiency     

Theoretical and experimental study of the input impedance of thecylindrical cavity-backed rectangular slot antennas

The authors study the input impedance of a cylindrical cavity-backed slot antenna based on mode matching and the complex Poynting theorem. Two cavity-backed slot antennas were fabricated to verify the theory. The numerical results agree very well with measurements. Two resonant frequencies were found from the input impedance. One resonant frequency is attributed to the rectangular slot and the other is due to the cavity. The slot length controls the first resonant frequency and has a much stronger effect on the input impedance at the antenna operating frequency as compared with the cavity length     

Aperture Coupled Rectangular Dielectric Resonator Antenna Array Fed by Dielectric Image Guide

This paper presents the design of a rectangular dielectric resonator antenna array coupled to narrow slot apertures that are fed by dielectric image guide (DIG). The DIG is excited by an X-band rectangular waveguide through a waveguide transition, and DIG tapering is used to match between the waveguide and the DIG. Reflection cancelling slots are added near the original slots to improve impedance matching. Since the slots radiate in both directions, a reflecting conducting plate is inserted above the DIG to decrease the back radiation of the antenna. The antenna is fabricated and the measured results are compared to the simulated results.      

波导阻抗带宽与缝隙导纳关系研究

本文从谐振阵等效网络出发,探索了缝隙波导谐振阵实现理想阻抗匹配的导纳特性,为波导谐振阵的超宽带设计提供了新思路.改进了波导并联缝隙的等效电路,首次实现缝隙导纳特性的单参数表征,创新提出了不同单元间距与单元数缝隙波导阵实现最大带宽的导纳特性分析方法,为波导缝隙阵带宽的优化设计提供了理论依据,建立了传统谐振阵非过载时的最大...     

Theory and experiment of the cavity-backed slot-excited dielectricresonator antenna

A slot-excited hemispherical dielectric resonator antenna backed by a rectangular cavity is studied theoretically and experimentally. The magnetic-type dyadic Green's function for the rectangular cavity is derived using the mode-matching method. An integral equation for the equivalent magnetic current is obtained by enforcing the boundary condition across the slot. The moment method with the Galerkin's procedure is then used to find the magnetic current in the slot and, hence, the input impedance of the antenna. Measurements were carried out to verify the theory and good agreement is obtained. The effects of the slot inclination angle, of the slot offset, and of the cavity size on the input impedance are discussed     

Theoretical study on the radial line transformer in a rectangular waveguide

A theoretical method is given for calculating the input impedance of the radial line transformer (RLT) in a rectangular waveguide. It is shown that this method is effective and can be used successfully in engineering applications.     

Input Impedance of a Probe Antenna in a TEM Cell

The input impedance of a probe antenna exciting a transverse electromagnetic (TEM) cell is analyzed via a variational formulation. The resulting impedance is shown to consist of two distinct terms; an ordinary rectangular waveguide contribution and a gap perturbation. Numerically generated curves for both are given and suggest that a simple algebraic approximation for the input impedance should normally suffice. The resistive portion is found to be proportional to the square of the probe length, while the reactive portion is largely capacitive. These results should enhance the use of probes inserted in TEM cells either to excite or to measure fields.     

Improved coupling for aperture coupled microstrip antennas

An aperture shape that gives significantly improved coupling for an aperture coupled microstrip antenna is described. This 'dogbone' aperture consists of the usual rectangular slot augmented with loading slots at each end. Measured data show an increase of more than three for the resonant input impedance of an antenna using the dogbone-shaped aperture, as compared with the input impedance of the same antenna with a rectangular slot of the same overall length. The field distributions of both slots are also measured, and compared.<>     

Compound coupling slots for arbitrary excitation of waveguide-fedplanar slot arrays

A resonant coupling slot cut in the common broad wall of two crossed rectangular waveguides is analyzed. The slot is offset from the center line and tilted with respect to the longitudinal axis of the main waveguide, whereas it is centered-tiled in the branch waveguide. It is shown that the slot offset and tilt control the branch waveguide excitation amplitude with a phase variability of 360°. Pertinent integral equations are developed, taking into account finite wall thickness. The integral equations are solved for the slot aperture electric field using the method of moments. Dominant mode scattering by the slot in both waveguides is obtained     

Transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with a dielectric slab

A compact and wide-band transverse slot antenna array in the broad wall of a rectangular waveguide partially filled with an H-plane -dielectric slab is presented in this paper. By partially filling an H-plane dielectric slab in the waveguide, the inter-element spacing between slots is reduced to be about 0.8 free-space wavelengths to avoid grating lobes. In addition, the partially filled material provides extra flexibility to adjust the slot impedance as desired within a relatively wide frequency range. A new feeding network is designed for this antenna array, which can prevent the shift in the pointing angle of the array's main radiation beam with the change of frequency. Experimental data for a 2/spl times/4 antenna array operating at X-band show that stable radiation pattern over a wide frequency range can be obtained. The measured gain is 16.9 dB at 10 GHz and the fluctuation is less than 2 dB over a frequency band of 1.5 GHz. The slot array's 10-dB return loss bandwidth is 13% and the cross-polarization level is better than -25 dB.     

The input impedance of a hollow-probe-fed, semi-infiniterectangular waveguide

Image theory is used to determine the input impedance of a coaxial feed in a short-circuited, semi-infinite, rectangular waveguide. The analysis is applicable to hollow antenna probes of variable height and lends itself well to accurate numerical evaluation. The numerical results are compared to results obtained from other methods and show the efficacy of using image theory to determine the waveguide input impedance     

应用于LMDS射频子系统中的一种矩形波导双工滤波器设计

LMDS(本地多点分配业务)是一种微波宽带技术，是解决“最后一公里”问题成本较低、功能较丰富的一种。本文设计了一种可用于LMDS中的采用加方形脊T形结的微波矩形波导双工器。介绍了矩形波导E面金属膜片滤波器的设计方法，这种滤波器的金属膜片可通过蚀刻等方法加工，加工精度高，成本低。对应用于双工器中的矩形波导H面T形结的特性进行了分析。     

A waveguide transverse slot for array applications

The characteristics of a radiating rectangular transverse slot in a rectangular waveguide have been studied. A moment method solution is used with entire basis expansion and testing functions (Galerkin) including the effect of wall thickness. The results are presented in terms of normalized resistance and reactance versus slot length and frequency. Excellent agreement with a previous pulse basis solution is found, as well as with measured data. An array of resonantly spaced transverse slots radiates large grating lobes. A spatial filter using baffles to suppress the grating lobes is described, suppressed. The effect of the baffles on the transverse slot impedance is analyzed for the case of baffles with infinite height     

A method of moments analysis and a finite-difference time-domainanalysis of a probe-sleeve fed rectangular waveguide cavity

A multifilament method of moments (MOM) analysis and a finite-difference time-domain (FE-TD) analysis are used to numerically calculate the input impedance of a probe-sleeve fed rectangular waveguide which has been short-circuited on one side. The input impedance of the system is determined by using the above methods for several probe-sleeve configurations, and reasonable agreement between the two methods for the cases studied is found. An MOM Green's function formulation which is based on scattering superposition and which allows the input impedance of a probe-sleeve feed to be calculated when the waveguide is terminated in a given load is derived. The MOM results and FD-TD numerical results are compared for this loaded waveguide input impedance case, and reasonable agreement between the methods is found. A comparison of theory and experiment is given for when the waveguide is terminated in a ground plane aperture     

Experimental investigation of the input-impedance characteristics of an antenna in a rectangular waveguide

The input impedance of a monopole antenna in a rectangular waveguide is investigated experimentally. It is found that theoretical results based on the assumption of a sinusoidal current distribution are in good agreement for monopole lengths up to about 0.6 of the guide height and about 1/4 ?0. For longer monopoles, a more accurate theory should be sought.     

Circularly polarized rectangularly bent slot antennas backed by arectangular cavity

Rectangularly bent slot antennas backed by a rectangular cavity for circular polarization are proposed. Characteristics of three types of cavity-backed rectangularly bent slot antennas for circular polarization-the single square loop slot, the two-element square loop slot, and the two-arm square spiral slot antenna-are analyzed numerically. The generalized network formulation based on the equivalence principle is given in terms of the method of moments. The magnetic currents on the thin rectangularly bent slots in the presence of the backing cavity are obtained and used to calculate the input impedance, radiation pattern, and axial ratio. Experimental results on the input impedance, radiation pattern, and axial ratio are in good agreement with calculated data