In this paper, the coupling coefficient of two waveguides with conducting interfaces is calculated analytically. It is shown that the control of interface charge densities via a transverse voltage leads to the control of the coupling. To derive the coupling coefficient, the basic Coupled Mode Theory (CMT) with paraxial approximation is improved to include the effect of conducting interfaces. The analysis is performed independently for TE and TM polarizations. Several direct applications of this effect including a multiplexer, a coupler and a modulator/switch and programmable grating are introduced.

n general, the maximum practical transferable power is different from the theoretical power, and in most cases much less. This is due to the role of factors related to the geometric shape of the structure, the characteristics of the emitted wave and the propagation environment of the waves. This article deals with practical considerations in transmitting maximum power in waveguides. In this paper, the theoretical principles of electrical breakdown in gases and consequently the maximum power hanling in waveguides as well as the factors that affect the power handling in waveguides are stated. Finally, a rectangular waveguide in the X band with the given wave characteristics and environmental conditions is investigated.

In this paper, we try to optimize the substrate-radiation/substrate-cladding (cover) radiation modes in terms of their performance parameters. It is well known that the guided modes can only be normalized. However, the radiation modes can also be normalized using the delta/Dirac function. We try to optimize the waveguide design parameters for the known cases to achieve performance as good as guided modes. The formal electromagnetic theory is applied to study the radiation modes. The normalization condition on radiation mode has been carefully used during analysis. The results are found to be satisfactory. It has been concluded that we can modify the performance of radiation modes according to our requirements. The performance is compared with the guided mode. The paper discusses guidelines to optimize the radiation modes for various constraints.

In this paper, we try to optimize the substrate-radiation/substrate-cladding (cover) radiation modes in terms of their performance parameters. It is well known that the guided modes can only be normalized. However the radiation modes can also be normalized by using the Delta/Dirac function. We try to optimize the waveguide design parameters for the known cases to achieve performance as good as guided modes. The formal electromagnetic theory is applied to study the radiation modes. The normalization condition on radiation mode has been taken care in to analysis. The results are found satisfactory. It has been concluded that we can modify the performance of radiation modes according to our requirements. The performance is compared with guided mode. The paper discusses guidelines to optimize the radiation modes for various constraints.

Waveguides, used in electronic industries, are structures for transferring electromagnetic waves. A twist waveguide is a device used to change the polarization of waves. In this study, a process for fabricating an aluminum rectangular twist waveguide was designed and some guidelines were introduced. The preliminary profile was obtained by a forward extrusion process. In order to study the effect of strain hardening, the twisting process was studied for annealed and non-annealed samples after the extrusion process. The results revealed the necessity of annealing the samples before the twisting; otherwise, local deformation would occur. Measuring the applied torque showed that as the process progressed, the required torque for an annealed sample would increase due to work hardening, while for a non-annealed sample the torque would decrease after local deformation. Furthermore, the simulation of twisting process was performed using Deform software. No inconsistency was observed between numerical and experimental results. Moreover, investigating the cross sectional distortion showed an undesirable cross sectional distortion for the unfilled sample whereas the cross section in the sand-filled sample stayed rectangular.

A full-wave electromagnetic analysis of microelectromechanical switches (MEMS) in microwave and millimeter waves is presented in this paper. The fields are obtained by solving Helmholtzs equation using HFSS which uses finite element method (FEM). The switch is assumed as a two- port structure and the S- parameters are deduced from the fields. Characteristics of the switch over 1-60 GHz band, i.e. insertion loss in ON state and return loss in OFF state are obtained as 0.02-1.22 dB and 14-60 dB respectively over 1-60 GHz range. The MEMS is also considered as a capacitor and is approximated with lumped elements. Using scattering parameters and the elements of the transmission matrix, the operation of the switch is analyzed and compared with the full-wave analysis results. Finally, the S-parameters for different dimensions and frequencies are determined. These characteristics are of great importance in computer aided design (CAD) of high frequency circuits.

Due to the growing demand for higher bandwidth, employing optical devices instead of electronic devices in data transmission systems has attracted much attention in recent years. Optical switches, modulators and wavelength converters are a few examples of the required optical devices. CMOS compatible fabrication of these devices, leads to much more growing of this technology. Optical pulse compression, is required for generating ultra-short pulses for high bandwidth optical transmission systems. In this work, we present a CMOS fabrication process compatible, integrated optical pulse compressor. A Silicon waveguide coated by MoS2 for nonlinearity enhancement is used for self-phase modulation and a chirped Bragg grating utilizing corrugated silicon waveguides is employed to achieve the required anomalous dispersion. Low power and high compression ratio were considered in this work. We achieved a compression ratio of 3. 5 by using a relatively low power optical pulse of 8W and a short waveguide length of 1mm.

In this paper a least square numerical method is presented for the solution of the junction of cylindrical waveguides. First, the electromagnetic fields in the input, output and the aperture waveguides are expressed by their modal expansions. Then, using the boundary conditions on the tangential electric and magnetic fields over the waveguide junction, an error function is constructed which is a positive definite quadratic function of the modal amplitudes. The unique minimum point of this error function may be obtained by the inverse of a hermitian matrix. This method of least squares (MLS) is applied to parallel- plate and also rectangular waveguide junctions including conducting diaphrgms. The outputs from computer implementations are compared with the data in the literature. In the present version of MLS similar to the method of moments for the solution of waveguide junction problems, the phenomenon of relative convergence appears where the relative number of modes in various sections of the waveguide has a definite effect on convergence of the numerical methods and should be selected in proportions to the size of the waveguides. On the other hand, in the customary method of least squares, a weighting factor appears in the error functions [1], which has a definite effect on the solution and the conservation of power and reaction should be used to determind its correct value. Therefore, there is an uncertainty of the solution of the waveguide junction problems by the various versions of the method of least squares, and it is necessary to adopt appropriate measures to reduce errors.

Rectangular waveguide is one of the earliest types of transmission lines. Rectangular waveguide can be produced byhot extrusion process. In this paper, the hot extrusion process of CuZn5 rectangular waveguide was investigated byFinite Element Method (FEM). In addition, Genetic Algorithm (GA) was used to optimize the die geometry and processconditions to achieve the lowest magnitude of extrusion force. Die geometry was introduced in terms of die length andbillet hole diameter under various frictional conditions. It was found that die length and billet hole diameter hadcontradictory effects on the extrusion force. The experimental study was also carried out to verify the accuracy ofestimated results.

The purpose of this research is to investigate the group velocity of tunable two-dimensional photonic crystals. The first step considers a square lattice consisting of dielectric rods in the liquid crystal background. In the next step, this structure was rotated by 45 degrees and its photonic band structure was investigated. Then, by removing a row of dielectric material (silicon) rods a waveguide is made in the photonic crystal. The waveguide mode and the related group velocity of the waveguide mode were investigated. In the following, the effect of applying an external voltage and changing the refractive index of the background material on the group velocity was studied. Afterward, by applying geometrical changes to the size of waveguide side rods, the effect of mentioned geometrical change on the properties of the waveguide mode and the group velocity was investigated. The calculation results show that the group velocity is reduced and as a result, the group index is increased.  The investigations carried out show that quantitatively, by applying an external voltage in the ordinary waveguides, the range of changes in the group index is between 7 and 10, but by applying changes in modified waveguides, this quantity changes in the range of 14 to 27, which can be adjusted by applying an external electric field.