A novel broadband design of a coplanar waveguide (CPW) fed T-shape slot antenna is proposed and experimentally studied. The size of the proposed antenna is reduced by over 26% compared to the reported wide slot antenna. The obtained results show that the impedance bandwidth, determined by 10-dB return loss, of the proposed slot antenna can be as large as 5690MHz or about 121% centered at about 4.695 GHz. The design considerations for achieving broadband operation of the proposed slot antenna are described, and experimental results are presented.

A microstrip bandpass filter with a new type of capacitive coupled resonator is presented. The filter is designed to be smaller compared to the same type of parallel-coupled bandpass filter. The filter is designed for a centre frequency of 2.5 GHz that lies in the S-band frequency range. The insertion loss at ƒ_o is 2.4 dB and the measured 3 dB bandwidth is 8.6%. The agreement between the predicted and measured results is excellent, and even the circuit simulator gives a very good prediction for the filter characteristics.

This paper presents a synthetic concept on eliminating crosstalk within multiconductor transmission lines (MTLs). Firstly, the method of moments (MoM) is used to calculate the per-unitlength (PUL) parameters of transmission lines. Secondly, the crosstalk is predicted using SPICE circuit simulator. Finally, three methods eliminating crosstalk are used synthetically to design the structure of MTLs. According to the results simulated with software, the effect on eliminating crosstalk by the synthetic design is quite satisfactory. Therefore, the concept may be implimented in practical engineering.

Experimental study on a cylindrical Dielectric Resonator Antenna (DRA) using barium titanate (BaTiO₃) is presented in this paper. The antenna is fed with a 50Ω microstrip transmission line at frequency around 2.5 GHz. High dielectric constant (ε_r = 1000) resonator samples with different thickness are employed. The return loss, input impedance and radiation patterns are studied. Design simulation results using CST software also presented.

Communication systems operating at frequencies above 10 GHz in equatorial climates are subjected to many fade occurrences due to heavy rain. Rain rate analysis using 1-minute data for 10 years (1996-2006) measurements in Penang shows that the rain exceeded 126.8mm/h for 0.01% of a year (R_0.01). Simultaneous measurements of Ku-band rain attenuation give A_0.01 as 22 dB. The rain rate and attenuation are characterized by the presence of breakpoints in the respective exceedance curves. The attenuation exceeds the fade margin for about 8.8 hours in a year.

A non-coherent theoretical model of sea-ice thickness with air-borne microwave radiometer (ABMR) was deduced based on the analysis of air-ice-water three-layer media. In the model, the highorder item of the brightness temperature was expressed and obtained. From the analysis of the penetration depth of sea-ice and its high-order item in the model, we found that ABMR with a wavelength can only be used to detect a certain range of sea-ice thickness. The maximum detectable sea-ice thickness is dependent on wavelength and precision of ABMR, whereas the minimum detectable sea-ice thickness is only related to wavelength. On this basis, the detectable sea-ice thicknesses of ABMR were calculated. The results were given on the selection of suitable ABMRs in different sea-ice conditions when ABMR is used to detect the ice thickness in Bohai Sea.

High frequency field expressions for a two dimensional reflector are derived. The reflector is placed in a homogenous and reciprocal chiral medium. Since geometrical optics fails at caustics so Maslovs method has been used to find the field expressions which are also valid around caustics. Examples of parabolic and circular reflectors have been considered.

This work demonstrates an efficient and simple PML absorbing boundary conditions (ABCs) implementation for the highorder extended-stencil M24 FDTD algorithm. To accomplish this objective, the integral forms of the PML split-field formulations were derived and discretized using the same M24 weighted multiple-loop approach, resulting in ABC performances that match the standard FDTD-based PML formulations. This proposed approach eliminates the impedance mismatches caused by switching from M24 to regular FDTD update equations within the PML regions and the necessary cumbersome subgridding implementations needed to minimize the effects of these mismatches. It also eliminates the need to use large separations between the scatterers and the PML regions as a simpler though more costly alternative. This achievement coupled with the recent effective resolution of the PEC modeling issue finally eliminates the last hurdles hindering the wide adoption of the M24 algorithm and its three-dimensional counterpart, the FV24 algorithm, as a viable option for accurate and computationally efficient modeling of electrically large structures.

A novel technique for the amplification and the compression of an optical pulse is proposed.Based on cascaded a semiconductor optical amplifier (SOA) and a nonlinear optical loop mirror (NOLM), the chirping effect induced by the SOA and the cross phase modulation effect between the signal pulse and control pulse can be utilized to shape the pulse.The picosecond pulse amplification and compression are demonstrated in this paper.A good theoretical model is designed with optimal parameters.Results show that the output signal pulse with high peak power, narrow pulse width, and low pedestal can be obtained using the designed model, which is suited for furture 640 Gbps optical communications.

This paper is devoted to the forward radar propagation over clean and contaminated seas, using the Ament model and by taking the shadowing effect into account. The well-known Rayleigh parameter, which characterizes the degree of roughness of a corrugated surface for the case of reflection on a rough surface, is presented. Then, it is extended to the transmission through a rough surface, and to the reflection on a layer of two rough interfaces. This extended Rayleigh parameter allows then to calculate the forward radar propagation over oil slicks on sea surfaces, using the Ament model. Moreover, the model is improved by taking the shadowing effect into account. Numerical results of contaminated seas are presented, and compared to that of clean seas.

Various electromagnetic scattering approximations beyond the Born assumption have been published during the recent years. This paper introduces a simple framework of analyses and investigates in a systematic way the fundamentals of the proposed theories. Our main focus is to demonstrate the link and similarities between the different scattering approximations employing a common physical basis. Based on analogies established we try to bridge the apparent gap between existing theories as well as introducing possible extensions and refinements.

A detailed study of surface TM modes at the interface between an isotropic medium and a uniaxial plasma is presented. Four cases for the isotropic medium, including normal, Left-handed, magnetic, and metallic media, are considered. The conditions for the existence of surface modes in each case are analyzed, showing that the existence is determined by the parameters of media, working frequency, and the direction of the principle axis. The Poynting vector along the propagating direction is also calculated. Depending on the media parameters and the frequency, the surface mode can have time-average Poynting vector in the opposite direction of the mode phase velocity.

The rain attenuation in the 12-GHz band and one-minuterain rate were measured at four satellite beacons located in South East Asia countries over a three-year period (2002-2004). The cumulative distribution of rain rate obtained as well as cumulative distribution of rain attenuation obtained are presented and compared with the rain prediction models. Most of the rain prediction models showed noticeable deviation to the measured values above the existence of the breakpoint (the point at which the slope changes). The results can be employed to guide the design and application of slant-path communication systems, especially in South East Asia countries.

A new computationally efficient algorithm for reconstruction of lossy and inhomogeneous 1-D media by using inverse scattering method in time domain is proposed. In this algorithm, cosine Fourier series expansion is utilized in conjunction with finite difference time domain (FDTD) and particle swarm optimization (PSO) methods. The performance of the proposed algorithm is studied for several 1-D permittivity and conductivity profile reconstruction cases. Various types of regularization terms are examined and compared with each other in the presented method. It is shown that the number of unknowns in optimization routine is reduced to about 1/3 as compared with conventional methods which leads to a considerable reduction in the amount of computations, while the precision of the solutions would not be affected significantly. Another advantage of the proposed expansion method is that, since only a limited number of terms are taken in the expansion, the divergence of the algorithm is far less likely to occur. Sensitivity analysis of the suggested method to the number of expansion terms in the algorithm is studied, as well.

A new type of antenna named as compound box-horn antenna is designed and analyzed for its radiation pattern. The present analysis is based on plane wave spectra for three-dimensional fields. The compound box-horn antenna is obtained by combining modified box-horn and pyramidal horn antennas, in which modified box-horn is coupled to pyramidal horn to excite TE₁₀- and TE₃₀- modes at the input of pyramidal horn. Thus, the compound boxhorn antenna has properties and advantages of both the modified box-horn and pyramidal horn antennas. The radiation patterns and corresponding half-power beam widths (HPBWs) of compound boxhorn antenna in free-space are computed at 10 GHz and compared for different flare angles in E- and H-planes of larger size pyramidal horn section of the compound box-horn. The results for HPBWs in Eand H-planes demonstrate that the radiation patterns in E- and Hplanes for compound box-horn can be made narrower by decreasing the flare angles in both E- and H-planes of larger size pyramidal horn section of the compound box-horn. The radiation patterns of compound box-horn are also compared with those for TE10-mode pyramidal horn of same aperture size and it found that the former horn is narrower in E- as well as H-plane than the latter. The analysis has been validated against the experimental results available in the literature. The work presented here can provide useful design guidelines for development of prototypes of compound box-horn which may find potential application as a high-directivity transmitting horn for antenna measurements in the laboratory or as a range illuminator, or in microwave communication etc.

Maxwell's equations are solved to determine transient electromagnetic fields inside as well as outside a large conducting plate of an arbitrary thickness. The plate is carrying a uniformly distributed excitation winding on its surfaces. Transient fields are produced due to sudden interruption of the d.c. current in the excitation winding. On the basis of a linear treatment of this initial value problem it is concluded that the transient fields may decay at a faster rate for plates with smaller value of relaxation time. It is also shown that the energy dissipated in the eddy current loss may exceed the energy stored in the initial magnetic field.

Awideband E-shaped microstrip patch antenna has been designed for high-speed wireless local area networks (IEEE 802.11a standard) and other wireless communication systems covering the 5.15-5.825 GHz frequency band. Two parallel slots are incorporated to perturb the surface current path, introducing local inductive effect that is responsible for the excitation of the second resonant mode. The length of the center arm can be trimmed to tune the frequency of the second resonant mode without affecting the fundamental resonant mode. Acomprehensiv e parametric study has been carried out to understand the effects of various dimensional parameters and to optimize the performance of the antenna. Asubstrate of low dielectric constant is selected to obtain a compact radiating structure that meets the demanding bandwidth specification. The reflection coefficient at the input of the optimized E-shaped microstrip patch antenna is below -10 dB over the entire frequency band. The measurement results are in excellent agreement with the HFSS simulation results.

Fractional curl operator is utilized to construct the solutions corresponding to fractional dual rectangular waveguides. Fractional dual rectangular waveguides may be considered as intermediate of two given waveguides, where both waveguides are related through principle of duality. Characteristic impedance of fractional waveguide is determined. Behavior of field lines in transverse plane is also investigated.

This paper presents a complete ray-tracing based model which takes into account scattering from rough surfaces in indoor environments. The proposed model relies on a combination between computer graphics and radar techniques. The paths between the transmitter and the receiver are found thanks to a Bi-Directional Path-Tracing algorithm, and the scattering field after each interaction between the electromagnetic wave and the environment is computed according to the Kirchhoff Approximation. This propagation model is implemented as a plug-in in an existing full 3-D ray-tracing software. Thus, we compare the results of classical ray-tracing with those of our model to study the influence of the scattering phenomenon on the wave propagation in typical indoor environments.

In this paper a novel intelligent method to identify an unknown medium (type of apodization and chirping) is developed. Our consideration is concentrated on complex fiber Bragg Gratings. For realization of the idea the Genetic Algorithms (GAs) is used. So, GAs is used to solve inverse scattering problem for reconstruction of nonuniform or complex fiber Brag gratings. In this method, the reflection coefficient measured in practice is inserted to a suitable algorithm. According to the proposed method, first medium discrimination is performed between predefined large classes of mediums and then the whole and necessary parameters for reconstruction of the medium are extracted. Full numerical method is used for compare of the results obtained from the presented algorithm. Our simulation shows good agreement between them. So, a novel method for identification and discrimination of optical mediums especially complex Bragg Gratings is presented. Finally the presented method can be used to identify optical mediums and complex Bragg Gratings systems.