Diffraction of an electromagnetic plane wave from a slit in an impedance plane placed at the interface of two different media, has been formulated rigorously. Both the principal polarizations are considered. The method of analysis is Kobayashi Potential (KP). To determine the unknown weighting functions, boundary conditions are imposed which resulted into dual integral equations (DIEs). These DIEs are solved by using the discontinuous properties of Weber- Schafheitlin's integrals. The resulting expressions are then expanded in terms of Jacobi's polynomials. The problems are then, reduced to matrix equations with infinite number of unknowns whose elements are expressed in terms of infinite integrals. These integrals are hard to solve analytically. The integrals contain poles for particular values of surface impedance and are solved numerically. Illustrative computations are given for far diffracted fields and other physical quantities of interest. To check the validity of our work, we compared the far field patterns with those of obtained through Physical Optics (PO). The agreement is good.
The reliable design of a satellite communications network, operating at Ku band and above, requires the exact evaluation of the interference effects on the availability and performance of both the uplink and downlink. In this paper, the case of Uplink Adjacent Satellite Network Interference is examined. We accurately calculate the deterioration of the uplink clear sky nominal adjacent satellite network Carrier-to-Interference threshold, due to spatial inhomogeneity of the propagation medium. At these frequency bands, rain attenuation is the dominant fading mechanism. Here we present an analytical physical model for the calculation of Interference Statistical Distribution between adjacent Broadband Satellite Networks operating at distances up to 500 km. We employ the unconditional bivariate lognormal distribution for the correlated rain fading satellite channels. Useful numerical results are presented for satellite networks located in different climatic regions and with various quality of service (QoS) assumptions.
Method of Moments (MOM) combining with the Kirchhoff Approximation(KA) for analysis of the problem of optical wave scattering by a stack of two one-dimensional Gaussian rough interfaces is solved. The scattered field from the upper interface is solved by MOM and the transmitted field from the lower one is expressed from the Kirchhoff approximation where the multiple scattering phenomenon is neglected. The advantage of this hybrid method is that it is more exact than Kirchhoff approximation. The two rough interfaces separate three lossless and homogeneous media. The bistatic scattered field and the scattering coefficient are derived in this paper for vertical and horizontal polarizations. The influence of the relative permittivity, the height rms and the correlative length, the average heights between the two interfaces on the bistatic scattering coefficient is discussed in detail. The application of this work is the study of electromagnetic modeling of oil slicks on ocean surfaces.
This paper presents an improved method for microwave nondestructive dielectric measurement of layered media using a parallel-plate waveguide probe. The method bases on measuring the S parameter S11 or reflection coefficient from the N-layer media over the range of 1 to 10 GHz. Formulation for the aperture admittance is presented which allows the solving of the inverse problem of extracting the complex permittivity for two cases of the media, (1) one that terminates into an infinite half-space, (2) one that terminates into a sheet conductor. Our theoretical analysis allows the study of the effects of air gaps and slab thickness on the probe measurements. Through numerical simulations, the ability to use the proposed method for dielectric spectroscopy and thickness evaluation of layered media is demonstrated.
The efficient algorithm is presented for the analysis of electromagnetic scattering from composite structures with coexisting open and closed conductors. A hybrid combined-field integral equation-the improved electric-field integral equation (CFIE-IEFIE) formulation with the incomplete LU factorization (ILU) preconditioner is proposed. Numerical results are given to demonstrate that the efficiency of our algorithm can be significantly improved when compared with the conventional EFIE formulation and the hybrid CFIE-EFIE formulation.
In this paper, a fast and efficient method based on MOM is proposed for the analysis of antenna and array mounted on bodies of revolution. An attachment mode is introduced to ensure the continuity of current density at the junction region between wire antenna and cylindrical surface. A method based on suitable changes of coordinates and domains is presented to extract singular point of the self-impedance element calculation at junction region and accurate impedance can be obtained. Taking the antennas and array mounted on a finite solid conducting cylinder as an example, the impedance characteristics and radiation pattern are calculated. The good agreement between the results obtained by using the analysis method presented in this paper and those of CST and NEC software reveals the accuracy and high efficiency of this method.
This paper is addressed to a design of K-band dual mode radar used in traffic information collection. The radar can work in both Frequency Modulate Continual Wave (FMCW) mode and Continual Wave (CW) mode. As VCO is seldom used as the oscillator in CW radar for velocity measurement, this paper studied the effect of phase noise and detecting distance on velocity error in CW mode in VCO design. The analysis shows that the effect of phase noise on velocity error can be reduced by shortening the detecting distance. There's little difference in short-range velocity measurement between the dual mode radar with MMIC VCO and the CW radar with low phase noise oscillator.
Off-axis ellipsoid reflector based off-focus configuration for deastigmatism and circularization of an elliptical Gaussian beam is proposed. Mostly used off-axis ellipsoid reflector based conventional configuration is constructed by aligning the incident direction directed to one focus of the ellipsoid, which reflect the output beam to the another focus of the ellipsoid. However, such configuration is unavailable to deastigmatize and circularize an elliptical Gaussian beam. Therefore, the coupling efficiency between the reflected beam and an essentially circular beam is not well satisfied. In this case, an off-axis ellipsoid reflector based off-focus configuration is proposed to obtain better coupling efficiency. Different from the conventional configuration, in the proposed off-focus configuration, the incident beam direction is diverged from one focus of the ellipsoid. As a result, the coupling efficiency of no less than 99.9% (as compared with coupling efficiency of about 94.2% based on conventional configuration) can be obtained, which is verified with numerical calculations.
Electromagnetic scattering of two or more incident plane waves has been investigated for a perfect electromagnetic conductor (PEMC) circular cylinder, coated with a metamaterial havingneg ative index of refraction. The incident waves are considered for both the TM and TE cases in the analysis. The scattered fields are calculated by the application of appropriate boundary conditions at the interfaces between the different media. It is assumed that both the PEMC cylinder and the coatingla yer are infinite alongthe cylinder axis. The numerical results are compared with the published literature, and are found to be in good agreement.
Utilization of electromagnetic band-gap (EBG) structures is becoming attractive in the electromagnetic and antenna community. In this paper, the effects of a two-dimensional electromagnetic bandgap (EBG) Structures on the performance of microstrip patch antenna arrays are investigated using the Ansoft High Frequency Selective Simulator (HFSSTM). A mushroom-like EBG structure is compared with 2-DEBG Structures. HFSSTM is employed to determine the effects of different Structures on two element microstrip patch antennas array. Two element microstrip patch antenna array on a uniform substrate suffer from strong mutual coupling due to the pronounced surface waves. Therefore, diverse forms of 2-DEBG Structures like: little number of holes, large number of holes, defect mode and different number of mushroom-patches columns structure are discussed. The two element microstrip patch antennas array placed on a defect in the electromagnetic (EBG) substrate that localizes the energy under the antennas. The excitation frequency of the two element microstrip patch antennas array near the resonance frequency of the defect mode can be used to control the coupling between antennas that are placed in an array. The mutual coupling improved by using large number of mushroom-patches columns structure.
A no-load induction motor under static eccentricity is modeled using time stepping finite element (TSFE) method; current, torque, and speed signals of the motor are obtained by finite element method (FEM) and used for static eccentricity fault diagnosis and analysis. The frequency spectrum analysis of the stator current around fundamental frequency component is used to predict the static eccentricity. Noise, unbalanced magnetic pull (UMP) and arc occur during the starting of the faulty motor, therefore, performance of the motor over the period of starting up to the steady-state is investigated. It is shown that the rate of obtained signals from the constant permeability based analysis is very larger than that of the real case. It is indicated that in order to obtain accurate results the saturation must be taken into account in the analysis of the motor. Simulation results for a 3 hp, three-phase, 230 V, 36 stator slots induction motor with 28 rotor slots are given in this paper. Experimental results for the motor confirm the simulation results very well.
Electrostatic velocity shear Kelvin-Helmholtz instability has been studied for bi-Maxwellian plasma in the presence of perpendicular a.c. electric field by using the method of characteristic solution. The effects of a.c. electric field temperature variation, velocity shear scale length,electron ion temperature ratio and other parameters on growth rate have been discussed.
In this work, a generalized procedure is carried out for the design of a microwave amplifier. First of all, the Performance Data Sheets (PDS) resulted from the active device characterization are used as Feasible Design Target Space (FDTS). Employing the PDS, the compatible (Noise F, Input VSWR Vi, Gain GT ) is determined over the predetermined bandwidth B between fmin and fmax operation frequencies with the source ZS and load ZL terminations as the design target. In the design stage, the Simplified Real Frequency Technique (SRFT) is utilized in the scattering-parameter formulation of the front- and back-end matching two-ports to provide the source and load terminations to the transistor, respectively. As an application example, a novel high technology transistor is chosen and the design targets are determined using the PDSs of the device and its frontand back-end matching two-ports are characterized by the scatteringparameters using the novel SRFT for each design target. Furthermore, the performances of the resulted amplifier circuits are analyzed and compared with the simulated results.