Variational analysis of inclined slots in the narrow wall of arectangular waveguide

A variational analysis for calculating the admittance of the inclined slots in the narrow wall of a rectangular waveguide is presented. The analysis uses the 90° wedge Green's function to model the scatterings off the waveguide corners and assumes an equiphase half-cosinusoidal electric field distribution along the slot aperture. Based on these, a variational equation is derived for the reflection coefficient due to the slot discontinuity, from which the slot admittance is calculated. Through comparisons between the computed results and the literature results, the analysis is found to be accurate, reliable, and efficient     

Resonant conductance of inclined slots in the narrow wall of a rectangular waveguide

A method to determine the admittance and resonant length of an inclined slot in the narrow wall of a rectangular waveguide is presented. An expression for the admittance of the slot is derived using an angular spectrum of planewaves and the discontinuity in modal current. When the depth of cut in the top and bottom wall is assumed to be zero, the expression for resonant conductance found by the present method is exactly the same as that obtained by Stevenson. Comparison between the theoretical and experimental results on the variation of resonant conductance with angle of inclination of slots for a fixed depth of cut of 3.5 mm is presented.     

矩形波导窄边缝隙分析方法述评

对矩形波导窄边缝隙的各种分析方法进行了综述,并指出了它们存在的问题。从中可以看到这一问题的理论分析方法的进步和尚需解决的问题。     

Admittance and resonant length of inclined slots in the narrow wallof a rectangular waveguide

The admittance properties and the resonant length of an inclined slot in the narrow wall of a rectangular waveguide have been investigated. The depth of cut of the slot in the broad walls of the waveguide has been taken into account. The internal power storage in evanescent modes in the waveguide, neglected in previous studies, is included. Theoretical results for the variations of conductance and resonant length with the angle of inclination of slots are presented. Through comparisons of the calculated results with previously available experimental data, the importance of the inclusion of the waveguide internal power storage is emphasized     

Circularly polarised radiation from narrow wall slots in rectangular waveguide

Slots in rectangular waveguides are often used at elements in linear array antennas. The polarisation of the radiated energy is usually linear. Circular polarisation can be obtained with compound slots in the broad wall. Experiments have shown that circular polarisation can be obtained from certain I-shaped slots in the narrow wall.     

A generalized analysis for a class of rectangular waveguide coupleremploying narrow wall slots

A comprehensive analysis is presented which is applicable to the general class of waveguide couplers comprising a dissimilar pair of rectangular waveguide coupled by means of an inclined slot on the narrow wall of the primary waveguide. An entire domain moment method is used to solve a pair of coupled-integral equations for the tangential electric fields on the surfaces of the slot. Three typical examples have been examined to demonstrate the validity of the method. The numerical results are shown to be in good agreement with those obtained from independently procured theoretical evidence and measurements     

Analysis of wide transverse inductive metal strips in a rectangularwaveguide

An analysis based on the variational method and the moment method has been developed to calculate the discontinuity susceptance due to one or more inductive strips in a rectangular waveguide. The strips can have wide widths and be located unsymmetrically on the transverse plane of the waveguide. The current distribution on the strips has been determined by solving a set of linear equations. The theoretical results agree closely with the experiments     

Improved Locally Conformal Finite-Difference Time-Domain method for edge inclined slots in a finite wall thickness waveguide

An Improved Locally Conformal Finite-Difference Time-Domain (ILC-FDTD) method is presented in this paper, which is used to analyze the edge inclined slots penetrating adjacent broadwalls of a finite wall thickness waveguide. ILC-FDTD not only removes the instability of the original locally conformal FDTD algorithm, but also improves the computational accuracy by locally modifying magnetic field update equations and the virtual iterative electric fields according to the complexity of the slot fringe fields. The mutual coupling between two edge inclined slots can also be analyzed by ILC-FDTD effectively.     

General analysis of narrow strips and slots

The general problems of TE- and TM-excited slots in screens and conducting strips whose widths are narrow relative to the wavelength are investigated. The narrow width approximation is imposed upon the slotted-screen and strip equations from which result approximate equations that are solved exactly. For general excitation, solutions are presented for both polarizations as products of series of Chebyshev polynomials and appropriate singular functions exhibiting the known edge condition. Special attention is afforded the problem of the slot/strip excited by illumination which can be represented by two terms of a Taylor series due to the practical importance of this situation.     

Moment method analysis of sidewall inclined slots in rectangularwaveguides

The main feature is the use of a 90° wedge Green's function to model the external coupling between the parts of the slot in the narrow and broad walls of the waveguide. The aperture field distributions of the inclined slots are solved directly. It is found that for resonant slots, the aperture field is approximately of constant phase, while its amplitude is nearly sinusoidal but with a slight tilt. From the field distribution, various characteristics of the slot can be extracted, such as the conductance, susceptance, and resonant length. The numerical computations are in good agreement with experimental results available in the literature     

Efficient modelling of multiple wide slots on coaxial antenna

An improved fixed gap model is proposed for multiple wide slots in coaxial antennas. The mutual coupling and the nonuniform distribution of the electric fields in the slots are considered. The calculated results are in good agreement with experiments     

Electromagnetic transmission through narrow slots in thick conducting screens

The general formulas for electromagnetic transmission through an infinitely long slot in a perfectly conducting screen of finite thickness are specialized to the case of a narrow slot. The slot may be filled with a homogeneous isotropic material. A simple equivalent circuit for the narrow slot is developed. It is found that for certain screen thicknesses the slot becomes resonant, and exceptionally large transmission of energy may occur. In fact, as the slot width approaches zero, the transmission width at resonance becomes1/piwavelengths regardless of the actual slot width. The effect of loading the slot with a lossy dielectric is also considered. Computations are given to illustrate the validity of the equivalent circuit model and the accuracy of transmission characteristics computed from it.     

The impedance properties of dielectric-covered narrow radiating slots in the broad face of a rectangular waveguide

An extension of Oliner's theory is used to predict the impedance of slots with dielectric coatings. Theoretical curves are presented which show the change in impedance as a function of dielectric constant, dielectric losses, and dielectric thickness. The effect of a dielectric or plasma upon the resonant frequency is also included. The agreement with experimental dielectric-covered slot data justifies the extension of Oliner's theory.     

Hot-carrier stressing damage in wide and narrow LDD NMOStransistors

Hot-carrier stressing has been carried out on LDD (lightly doped drain) NMOS transistors with gate width as a variable. It is found that the damage is qualitatively different between the wide and narrow devices. To investigate the poststress damage, use is made of a hole injection phase to neutralize any trapped charge. It is shown that the narrow devices degrade predominately by charge trapping, whereas the wider devices show interface-state creation. It is further shown that the localization of the hot-carrier damage is different, being extended towards the source for electron trapping in the narrow devices, whereas the wide devices show interface states localized at the drain junction edge. It is suggested that the mechanical constraints arising from the proximity of the bird's-beak structure are responsible for the electron-trapping behavior     

Coupling by slots in rectangular waveguides with arbitrary wall thickness

A method for evaluating the coupling between two rectangular waveguides, coupled by a slot of arbitrary dimensions in a wall of arbitrary thickness is described. The method is based on the solution, by numerical techniques, of a pair of coupled integral equations. Results for typical shunt and series slots are presented.     

NUMERICAL STUDIES ON RESONANT AND ENHANCEMENT EFFECTS FOR COUPLING OF MICROWAVE PULSES INTO NARROW SLOTS

In this paper, modifications to the finite-difference time-domain(FD-TD) method for modeling microwave pulse coupling into a slot, which is much narrower than one conventional FD-TD cell, are discussed. The coupling process of microwave pulse into a slot is studied by using the modified FD-TD method, and the dependence of microwave coupling on slot sizes, the carrier frequencies and the polarization directions of the incident waves is analysed. Resonant and enhancement effects which occur in this process are observed. The condition at which the resonant effect takes place is also presented.     

Compound radiating slots in a broad wall of a rectangular waveguide

An analysis is presented of the characteristics of a broad wall radiating slot, offset from the center line and tilted with respect to the longitudinal axis of a rectangular waveguide. Pertinent integral equations are developed, taking into account finite wall thickness, and are solved for the slot aperture E-field using the method of moments. Compound slot characteristics are then deduced, including resonant length and dominant mode scattering. Numerical results for the scattering from resonant slots are presented over a range of offsets, tilt angles, frequencies and waveguide dimensions. For resonant compound slots, offset and tilt are shown to control the aperture electric-field amplitude with a phase variability of 360°. The results have significant applications in the design of compound slot arrays     

Analysis of edge slots in rectangular waveguide with finitewaveguide wall thickness

A novel analysis for computing the admittance characteristics of edge slots with a salient feature in successfully considering the finite waveguide wall thickness is presented. The variational equation for the electric field in the slot region between the inner and outer waveguide walls is derived by applying the variational reaction theory and solved by the finite-element method. The division of the slot region into small elements of triangular cylinders and the basis function for each element are described in detail. In the limiting case of zero wall thickness, this finite-element analysis is reduced to a moment-method analysis using Galerkin's approach with triangular basis functions. The effects of waveguide wall thickness on the characteristics of the slot are investigated by comparing the numerical results with and without considering the wall thickness. Negligence of the wall thickness may result in a severe underestimation of the resonant length by as large as 14% for edge slots cut in typical X-band waveguides. The computed results with the finite wall thickness taken into account have been checked with the measured data published in previous literature and those obtained by a carefully devised experimental setup. Good agreement between theoretical and experimental results is obtained to demonstrate the validity of the analysis     

Efficient and accurate evaluation of external mutual couplingbetween compound broad wall slots

The efficient and accurate evaluation of external mutual coupling between compound broad-wall slots cut in rectangular waveguides is addressed. The special case of longitudinal slots is also considered. Errors introduced by approximations used in some mutual coupling expressions are investigated and numerical results are presented for a range of waveguide and slot parameters. It is shown that for most applications, mutual coupling expressions can be determined in terms of single numerical integrals