Magic tee is a widely used component in microwave systems; the four arms of a conventional magic tee direct at four different directions, which occupy much space and give inconveniences to the assemblage of a system. In this paper, a waveguide narrow-wall slot directional coupler and an E-plane dielectric loaded waveguide phase shifter are used to make up of a magic tee with four arms in the same H-plane. The narrow-wall slot directional coupler is analyzed with mode matching method and optimized with simulated annealing method, and the dielectric loaded waveguide phase shifter is designed with edge based finite element method. Numerical results of the magic tee are presented, which show that the performance of the designed magic tee is good.

This paper reports the miniaturization of a microstrip 90 degree coupler by substituting the quarter wave transmission lines employed in conventional 90 degree coupler with its equal circuits consisting of two oblique stubs and an inductor and capacitors. Reduction of the coupler to 27% its size is reported here. This coupler is designed at 1070MHz for using in even harmonic mixers of 3G mobile receivers. Furthermore, the coupler can accurately divide the input signal by two parts with the same power and 90 degree phase difference. Also, the reflection coefficient and the isolation are as good as conventional one and coupling procedure is better than it.

Finite-Difference Time Domain (FDTD) is used to calculate the input impedance of the cylindrical dielectric resonator (DRA) antenna with different dimensions. A lumped- element circuit model for the input impedance calculation is proposed. The genetic algorithm is used to calculate the elements of the equivalent circuit. The Model-Based Parameter Estimation (MBPE) technique is used to find the variation of each element in the equivalent circuit with varying the physical dimensions of the antenna. The use of this method reduces the time required for calculating the input impedance of the cylindrical DRA in eachv ariation of the antenna dimension.

This paper reports a high IIP3 even harmonic mixer with a new circuit configuration. This mixer employs an antiparallel diode pair, open and short circuited stubs and a radial stub as filters to separate RF input signal, Baseband output signal and LO Power. This mixer is used for down converting 3G Mobile downlink Signal at 2140MHz to BaseBand by using a local oscillator at 1070MHz in direct conversion configuration. This mixer must comply with the requirements specified by 3G UMTS: 3rd order Input Intercept Point = 14.466dBm ≥ 11 dBm, Noise Figure = 9 dB and Conversion Loss = 11 dB.

We consider the inverse problem of determining both the shape and the conductivity of an un-uniform conductivity scatterer buriedin a three-layer structure by the genetic algorithm. An ununiform conductivity scatterer of unknown shape and conductivity buriedin the secondla yer scatters the incident wave from the first layer or the thirdla yer. We measure the scatteredfieldin the first andthird layers. Based on the boundary condition and the measured scattered field, a set of nonlinear integral equations is derived and the imaging problem is reformulatedin to an optimization problem. The genetic algorithm is then employedto findout the global extreme solution of the object function. As a result, the shape andthe conductivity of the scatterer can be obtained. Numerical results are given to demonstrate that even in the presence of noise, good reconstruction has been obtained.

We use coordinate transformation theory to realize substrates that can modify the emission of an embedded source. Simulation results show that with proper transformation functions the energy radiated by a source embedded in these space variant media will be concentrated in a narrow beam. The thickness of the slab achieved with our transformations will no longer be restricted by the evanescent modes and the source can be placed at any position along the boundary of the substrate without affecting the radiation pattern. We also discuss the case where reduced parameters are used,whic h still performs well and is physically realizable.

From the analytical theory of rough surface Green's function based on the extension of the diagram method of Bass, Fuks and Itô, with the smoothing approximation, numerical results are presented for Gaussian and sea spectra and compared with a benchmark method by considering a one-dimensional perfectly conducting Gaussian rough surface. The effects of multiple scattering due to the surface roughness are incorporated systematically into the solutions through an effective surface impedance, which can be iterated up to the second-order. In addition, comparisons of the bistatic scattering coefficients are presented with the first- and second- orders conventional small perturbation method. This study will be useful for remote sensing of the ocean surface, especially when the transmitter is close to the surface.

A time reversal method is studied and adapted to through-the-wall detection and localization of moving targets. Tests are realised on experimental data in a synthetic aperture radar configuration. The efficiency of the method to extract a moving target from a cluttered environment is proved on experimental data.

This paper presents a very small size microstrip antenna suitable for WLAN application. The main patch antenna consists of an M-shaped slot with shorting wall. With a shorted triangular parasitic patch and a folded patch overall antenna size is reduced. The simulated and measured results show that by selecting a proper shorting wall width, the proposed antenna can provide an impedance bandwidth of 21.17% covering the 4.93-6.09 GHz band. The antenna size is of order 0.1094λo × 0.1094λo × 0.0544λo (6 × 6 × 3mm3). The proposed antenna has 75% surface size reduction compared to a conventional patch antenna operating at the same centre frequency. The E- and H-plane radiation pattern across the entire operating bandwidth is provided.

A new mathematical method and proposal for generation of shape invariant potentials using supersymmetric quantum mechanics is introduced. For this purpose the potential term in the Schrodinger equation is expressed in terms of the super potential. The obtained equation transformed into well known ordinary second order differential equation. Using standard technique, the Nikiforov-Uvarov (NU) method the superpotential in the Schrodinger equation is expressed in terms of the parameters appeared in the NU-approach concluding to a nonlinear differential equation. By solving the obtained equation and using relation between superpotential and potential the shape invariant potentials are obtained. The proposed method is general and straightforward for introducing of the shape invariant potentials.

In this paper, the problem of electromagnetic scattering from resistive strips is solved and discussed. This problem is modeled by the integral equations of the second kind. The basic mathematical concept is collocation method using block-pulse orthogonal basis functions. An effective numerical method for solving these integral equations is proposed. The problem of electromagnetic scattering from resistive strips is treated in detail, the illustrative computations are given for several cases, and an extensive discussion on the obtained results is performed. This method can be generalized to apply to objects of arbitrary geometry.

In this paper, full-wave analysis of a microstrip-ring resonator capacitively coupled to Microstrip transmission line is presented. The method of the analysis is based on spectral domain in rectangular coordinate system. Since this coordinate system is not compatible with ring structure, triangular basis functions have been utilized for the current distributions on the ring surface. Applying Galerkin's method in spectral domain, the resonant frequencies of the structure and current distributions on the conductors are calculated and the effects of various parameters are studied. To verify the method of analysis, our results are compared with others and the accuracy of the method has been confirmed.

Diffraction of a plane wave from a geometry which contains an infinite slit in a perfect electric conducting (PEC) plane and a perfectly electromagnetic conductor (PEMC) cylinder is presented. The method is based on the extension of Clemmow, Karp and Russek solution for the diffraction by a wide slit. The results are compared with the published work and agreement is fairly good.

This paper presents a new frequency-sweep approach for the efficient calculation of S-parameters of planar microwave structures. The approach is based on approximating the frequency dependence of the real and imaginary parts of the S-parameters using neural networks. Due to its superior performance, radial basis functions neural network (RBF-NN) is adopted. A limited number of frequency samples are used to train the RBF-NN. Then, the trained RBF-NN is capable of providing a smooth frequency response with very high accuracy in a fraction of a second. The proposed method is applied to a number of planar microwave structures such as: Patch antenna with an inset feed, band-rejection filter, and branch-line coupler. According to the presented results, a speed factor of at least 10 is measured, and a maximum percentage error of 3.29% is recorded.

This paper considers the influence of interchannel crosstalk on pulse timing shift and optical power due to the propagation of optical pulse through a nonlinear dispersive fiber. The numerical results are shown. An influencing parameter of the pulse distortion through the fiber is the eye opening penalty.

Feature extraction is a challenging problem in radar target identification. In this paper we attempt to exploit the sparse property of the scattering signature with a undercomplete dictionary for target identification, and establish a feature extraction scheme based on the undercomplete dictionary. Furthermore, as an application, we present a feature vector, named as the atom dictionary feature, which is extracted from the scattering signatures over a wide-angle sector. Numerical simulation results show that the proposed atom dictionary feature can improve the performance of radar target identification due to the exploitation of the sparse property of the scattering signature.

In this paper, we study in detail the electromagnetic field excited by a horizontal electric dipole in the presence of a four-layered region, which consists of a perfect conductor, the two dielectric layers, and air above. From the derivations and analysis, it is seen that the electromagnetic field includes four wave modes: Direct wave, ideal reflected wave, trapped surface wave, and lateral wave. The wave numbers of the trapped surface wave, which are determined by the residues of the poles, are between the wave number k₀ in the air and k₂ in the lower dielectric layer. The lateral waves with the wave number being k₀ are determined by the integrations along the branch cuts. It should be pointed out that both the trapped surface wave and lateral wave can be separated into the electric-type terms and magnetic-type terms. Analysis and computations show that the trapped surface waves play major roles at large propagation distance when both the dipole point and the observation point are on or close to the air-dielectric boundary.

Passive UHF RFID tag consists of a microchip attached directly to an antenna. Proper impedance match between the antenna and the chip is crucial in RFID tag design. It directly influences RFID system performance characteristics such as the range of a tag. It is known that an RFID microchip is a nonlinear load whose complex impedance in each state varies with the frequency and the input power. This paper illustrates a proper calculation of the tag power reflection coefficient for maximum power transfer by taking into account of the changing chip impedance versus frequency.

In this paper, the power dissipated through different loss mechanisms including dielectric, conductor and radiation loss is calculated for the substrate integrated waveguide (SIW) and modified substrate integrated waveguide (MSIW). The applied computational method being appropriate for structures with periodic conducting parts allows one to calculate the integrals corresponding to these powers analytically and with high accuracy.

In this paper we have reported soliton solution of one dimensional modified complex Ginzburg Landau equation. The parametric region where such soliton solution is possible is also identified.