In this paper a Polarized Optical Orthogonal Code (Polarized-OOC) is proposed by exploiting the polarization property of the fiber and the chip's polarization state. The polarized-OOC code is generated using the concept of Mark Position Difference (MPD) set. Polarized-OOC code cardinality is shown to be two times that of the conventional OOC which reflects an increase in the number of supported users. Furthermore, since the correlation properties of the constructed code are the same as that of conventional OOC, error rate performance is evaluated in the same way as in conventional OOC. Also, a simple procedure for fiber-induced polarization rotation compensation is introduced. We then use simulations to show that relative polarization axis misalignment between the desired user and interfering users leads to violation of the correlation properties of the proposed code.

The properties of a grounded dielectric slab with double negative (DNG) metamaterials are investigated in this paper. Dramatically different dispersion curves of evanescent surface modes (electromagnetic fields exponentially decay both in air and inside the slab) are observed. They are highly dependent on the medium parameters. As the counterpart of the improper complex leaky modes in a double positive (DPS) medium, the complex modes in a DNG medium are proved to be exclusively proper. They have exponentially decaying fields in the air region and are termed complex surface modes. It is found that there are an infinite number of complex surface modes and they cannot be suppressed. The Poynting vectors of complex surface modes are studied and it is proved that their integrals along the transverse direction are simply zero. The complete mode spectrum of the dielectric slab for both DPS and DNG media are tabled and compared. Surface wave suppression is discussed and its necessary and sufficient conditions are presented.

Based on a generalized Helmholtz's identity, definitions of an irrotational vector and a solenoidal vector are reviewed, and new definitions are presented. It is pointed out that the well-known uniqueness theorem of a vector function is incomplete. Although the divergence and curl are specified, for problems with finite boundary surfaces, normal components are not sufficient for uniquely determininga vector function. A complete uniqueness theorem and its two corollaries are then presented. It is proven that a vector function can be uniquely determined by specifyingits divergence and curl in the problem region, its value (both normal and tangential components) on the boundary.

In this paper, a conceptual schematic for calibration of large phased array antenna is presented. Derived from an earlier work by the authors, the presentation demonstrates a simple yet innovative schematic of inserting time delay units with each element in the array which can be used to generate both SUM and DIFFERENCE pattern. Both these patterns are electronically steerable. The calibration is done using SUM-DIFFERENCE pattern. PIN switches are used to insert proper time delay units. Thus the schematic is completely programmable using a microcontroller to control the insertion of time delay. The details of the schematic is presented along with the generated antenna patterns.

Geometry of grating structure has been analyzed to maximize electromagnetic energy deposition onto the active region of a silicon photodetector. The concept of Brewster angle to minimize reflection from the grating surface and a differences-in-time technique to focus incoming electromagnetic radiation on the substrate has been applied to optimize the grated structure that amplifies transmitted energy through grating-substrate interface. The computed electric field at the interface for the new grating geometry has been found to be approximately 1.5 times higher than that of a square-shape gratings reported earlier. Also the average power depositions and electric field distributions on the grating-substrate interfaces have been studied which revealed the superiority of the proposed optimum structure.

When the finite-difference time-domain method is used to compute waveguide structures, incident waves are needed for calculating electrical parameters (e.g., the scattering parameters), and effective absorbing boundary conditions are required for terminating open waveguide structures. The incident waves are conventionally obtained with inefficient three-dimensional (3D) simulations of long uniform structures, while the absorbing boundary conditions reported so far do not perform well at or below cut-off frequencies. To address the problems, we propose a novel one-dimensional (1D) finite- difference time-domain method in this paper. Unlike the other methods developed so far, the proposed method is derived from the finite-difference time-domain formulation, and therefore has the same numerical characteristics as that of the finite-difference time-domain method. As a result, when used to obtain an incident wave, it produces results almost identical to those produced by the conventional finite- difference time-domain method except computer rounding-off errors. When used as the absorbing boundary condition, it produces reflections of less than −200 dB in entire frequency spectrum including the cut-off frequencies.

Horizontal roll vortex pairs are dynamical structures that transfer energy and emissions from wildfires into the atmosphere. The vortices form at the edges of an intense line wildfire and emulate two cylinders, which form two curvatures of a biconcave thermal lens. Wildfire plume provides a dielectric material for the dielectric lens, whose permittivity is influenced by the nature, quantity of constituents (e.g., potassium and graphitic carbon) and variation of temperature with height in the plume. The environment created by the plume is radio sub-refractive with an effect of spreading radio wave beams. A numerical experiment was carried out to quantify loss of Ultra High Frequency (UHF) radio signal intensity when high intensity wildfire- induced horizontal roll vortices intercept UHF propagation path. In the numerical experiment, a collimated radio wave beam was caused to propagate along fuel-fire interface of a very high intensity wildfire in which up to two roll vortex pairs are formed. Maximum temperature of the simulated wildfire was 1200 K. Flame potassium content was varied from 0.5-3.0%. At 3.0% potassium content, a vortex pair imposed a maximum radio ray divergence of 2.1 arcmins while two vortex

This paper presents a planar microstrip-fed tab monopole antenna for ultra wideband wireless communications applications. The impedance bandwidth of the antenna is improved by adding slit in one side of the monopole,in troducing a tapered transition between the monopole and the feed line,and adding two-step staircase notch in the ground plane. Numerical analysis for the antenna dimensional parameters using Ansoft HFSS is performed and presented. The proposed antenna has a small size of 16 x 19mm,and provides an ultra wide bandwidth from 2.8 to 28 GHz with low VSWR level and good radiation characteristics to satisfy the requirements of the current and future wireless communications systems.

In this phase of the attempt to advance finite dimensional algebraic function approximation technique in eigenvalue problems of lossless metallic guides filled with anisotropic and/or inhomogeneous media,to exact analysis in infinite dimensions,it is seen that the problem in infinite dimensions,can be reduced to finite dimensions,b y virtue of a result in perturbation theory. Furthermore,it is found that analysis results of algebraic function approximation,can be adapted to infinite dimensions too,at worst by introduction of some additional arguments.

Theoretical results on the effect of antenna mutual coupling (MC) on capacity of multiple-input multiple-output (MIMO) wireless channels are presented in this paper with particular emphasis on the case of high signal to noise ratio (SNR) scenario. Two cases are considered, 1- channel capacity variations due to MC effect on correlation properties and target average receive SNR and 2- channel capacity variations due to MC effect on correlation properties at fixed average receive SNR. It is shown that the effect of MC on MIMO channel capacity can be positive or negative depending on the propagation environment spatial correlation properties and the characteristics of the transmitter and receiver MC matrices. Conditions where MC has positive and negative effects on MIMO channel capacity in the two considered cases are identified. Numerical results for half wavelength dipole antenna supporting the theoretical observations are presented.

A general method is proposed to analyze periodic or aperiodic Coupled Nonuniform Transmission Lines (CNTLs). In this method, the per-unit-length matrices are expanded in the Fourier series. Then, the eigenvalues of periodic CNTLs and so the S parameters of aperiodic CNTLs are obtained. The validity of the method is studied using a comprehensive example.

The rigorous modeling and analysis of electromagnetic wave transformation and radiation from the periodic boundary of metamaterial are presented. The nature of the phenomenon of resonant radiation and the influence of various parameters on it are investigated. The study is carried out with the objective of potential applications to antenna design. Simulated results show that very high directivity can be obtained and that beam steering can be achieved by adjusting proper parameters.

In this paper, a fast method is proposed to calculate wide- band frequency responses of complex radar targets on a personal computer. When frequencies are low, the frequency factor can be separated from space parameters by Chebyshev polynomial approximations of Green's function. Then, matrices from MoM at different frequencies can be rapidly filled, and monostatic RCS can be soon calculated. If frequencies are relatively high, a fast high-order MoM (HO-MoM), in which matrices products are in place of multi- dimension numerical integrations, is presented. That will reduce the CPU time requirement. Lastly, Numerical results are given for various structures and compared with other available data.

Two novel structures for high-Q MEMS tumble capacitors are presented. The proposed designs include full plate as well as the comb structured capacitors. They can be fabricated employing surface micromachining technology which is CMOS-compatible. The structures do not require the cantilever beams which introduce considerable series resistance to the capacitor and decrease the quality factor. Therefore, our proposed structures achieve better Q in a smaller die area. The simulated results for 1 pF full plate capacitor shows a tuning range of 42% and a Q of 47 at 1 GHz. However, with the same initial capacitance, but the comb structure, the tuning range is increased to 43% but the Q is decreased to 45 at 1 GHz. The simulated Pull-in voltage with no residual stress is 3.5 V for both capacitors. The S11 responses are reported for a frequency range from 1 up to 4 GHz.

This paper presents the study of a circular slot antenna for ultrawide-band (UWB) applications. Antenna is fed by a circular open ended microstrip line. The frequency band considered is from 4 to 14 GHz, which has approved as a commercial UWB band. The proposed antenna has a return loss less than 10 dB, phased linear, and gain flatness over the above a frequency band.

Based on the strict and delicate analogue relation between the magnetic moment of rotational charged bodies and the rotation inertia of rigid bodies, a new concept of charge moment tensor I which is different from the existent electric multiple moment is introduced in this paper. And by means of eigenvalue theory of tensor I , the concept of principal axes and principal-axis scalar charge moment are constructed, and further the scalar charge moment of a charged body and the magnetic moment of a rotational charged body around an arbitrary direction are attained. The relationship between the scalar charge moment distributive law of quadric camber and the positive or negative definiteness of tensor I are discussed. Meanwhile Some principles or theorems are extended, generalized, illustrated, and enumerated.

In this paper we show, theoretically, that total omnidirec- tional reflected frequency band is enlarged considerably by using one- dimensional photonic crystal (PC) structure composed of alternate lay- ers of ordinary material (OM) and left handed material (LHM). From the analysis it is found that the proposed structure has very wide range of omnidirectional total frequency bands for both polarizations in com- parison to the normal PC structure, which consists of alternate layers of ordinary material having positive index of refraction. The proposed structure also has an absolute band gap that can be exploited to trap the light.

This paper presents a simple and alternative approach for the analysis of inductive waveguide microwave components. The technique uses a surface integral equation formulation, in which the contours of the waveguide walls and of the inner obstacles are all discretized using triangular basis functions. In order to avoid the relative convergence problem of other techniques based on mode matching, an alternative port treatment is used. The technique is based on the application of the extinction theorem using the spatial representation of the Green's functions in the terminal waveguides. In addition, the Fast Multipole Method is proposed in order to reduce the computational cost for large problems. Different complex structures are analyzed, including microwave bandpass filters with elliptic transfer functions, waveguide bends and T-junctions. Results show the high accuracy and versatility of the technique derived.

Broken rotor bars and end-ring are common faults in three-phase squirrel-cage induction motors. These faults reduce the developed toque and increase the speed fluctuations of the motor. Meanwhile, developed unsymmetrical magnetic generates noise and vibration in the motor. Local heat around the broken bars may gradually break the adjacent bars and the motor will be finally out of service. Finite element method (FEM) is the most accurate technique for diagnosis and analysis of induction motor, because it can include all actual characteristics of the healthy and faulty induction motors. However, current density is generally considered as input for performance computation process, while fault can inject a large harmonics to the stator current. These harmonics may not be ignored in the fault diagnosis of the motor. In addition, all FE applications consider the steady-state mode of operation. In this paper, a three-phase voltage-fed squirrel-cage induction motor with rotor broken bars is proposed and analyzed for the starting period of the motor. Both no-load and on-load cases are considered. Also, concentrated rotor broken bars under one-pole and the distributed rotor broken bars under different poles are studied and compared.

In this paper, rain statistics of 10 years record in Taiwan area was used to investigate the transmission performance of the Ka- band LMDS system with QAM modulation. Emphasis was placed to investigate the effects of rain fading under M-QAM modulation schemes. It is found that for LMDS cellular network, M-QAM modulation is difficult to provide an effective and reliable high speed transmission for the case of 6 km radius of cell coverage unless the frequency and polarization diversities are applied; otherwise, the cell coverage of service should be shrunk.