An air-spaced coaxial-fed patch antenna to be used as a microwave sensor for non-destructive porosity measurements in lowloss dielectric materials is presented. The variation of the patch resonant frequency when it is put on the surface of the material under test is used to estimate the dielectric permittivity. Then, a standard two-phase mixture model is used to derive the material degree of porosity from the above permittivity estimate. Measurements at the 2.4 GHz ISM frequency band have been carried out on a set of polymeric samples with artificially induced porosity. The specific choice for the operating frequency is related to the final goal of applying the above microwave sensor for quality control of ceramic materials during the production process.

In this paper, an extremely fast technique is introduced to evaluate the shielding effectiveness of a rectangular enclosure of finite wall thickness and numerous square or circular small apertures subject to a normally incident plane wave. The technique is based on the traditional waveguide circuit model where the enclosure is replaced with an equivalent shorted transmission line. In the proposed circuit model, the perforated thick wall is represented by an equivalent impedance which is derived from the reflection coefficient. The computation results are in very good agreement with measurements. Additionally, further results are compared to a generalized modal MoM technique which are in excellent agreement as the number of apertures increase. Besides accuracy, the method is extremely efficient and easy to implement compared to the numerical techniques.

A geometrical high-frequency approximation method for solving the propagation of electromagnetic wave through the quartic Wood lens into an uniaxial crystal is presented in this paper. Caustic problem of electromagnetic wave is translated into non-caustic problem by using the hybrid space. The drawback that the solution in the caustic region cannot be obtained with geometrical optics is overcome by this method known as Maslov's method. The high-frequency approximation solution that is valid around caustic region is obtained by using this method which combines the simplicity of ray and generality of the transform method. And the results are compared with those obtained by Huygens-Kirchhoff's expression.

This paper presents the design and construction of an advanced wideband, automated radar system. With the aid of Vector Network Analyzer (VNA), a wideband ground-based system can be achieved with proper Radio Frequency (RF) circuitry integration. The RF circuitry is designed specifically to configure the proposed system to be able to measure full linear polarimetric scattering matrices of the area of in terest. Besides, quasi-monostatic horn antenna configuration is chosen to transmit and receive the electromagnetic wave. The goal of this paper is to demonstrate the real and synthetic aperture capabilities of the system in outdoor measurement with the microwave frequency range from 2 to 7 GHz. Coupled with the integration of the Automatic Antenna Positioning System (AAPS), the constructed system is able to perform real and synthetic aperture radar measurements. A series of measurement was done on real aperture radar measurement using point target for validity purpose. The overall results show good agreement with the theoretical values. On the other hand, the proposed system is capable to performing a radar imaging measurement. A preliminary analysis is done on a 45 days old rice field. A three dimensional (3-D) radar image has also been constructed successfully with Range Migration Technique (RMA). The result shows good potential ofthe system in constructing radar imaging ofnatural target.

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.

We propose an exact synthesis method which allows the design of dual-band transformers with an arbitrary even number of uniform sections giving equi-ripple impedance matching in two separate bands centered at two arbitrary frequencies. This method is a generalization of the exact Collin-Riblet synthesis of Chebyshev single-band transformers. As compared to a single-band Collin-Riblet transformer encompassing both required passbands, the proposed design yields significantly better performance in terms of passband tolerance and width.

A low complexity wavelet packet transform-based least mean square (LMS) adaptive beamformer is presented in this paper. This beamformer uses wavelet packet transform as the preprocessing, reduces the signal dimension in wavelet packet domain for low complexity and denoising, and employs least mean square algorithm to implement adaptive beamformer. Theoretical analysis and simulations demonstrate that this algorithm with better beamforming performance converges faster than the conventional adaptive beamformer and the wavelet transform-based beamformer. Finally, our proposed algorithm has the low complexity, and it can be easy to implement.

The problem of diffraction of a plane electromagnetic wave by a slot in a planar perfectly conducting screen of arbitrary thickness in the presence of a half-infinite dielectric arranged at a distance from a screen is solved rigorously on the bases of eigenfunction expansion and mode matching technique. The calculation algorithm for various components of the electric and magnetic field vectors in the entire space is presented, and a simple computation method for corresponding diffraction integrals is described. Just one more method of field visualization is demonstrated, which utilizes a picture of the energy-flux lines.

Making use of the Toeplitz structure of the mutual coupling matrix of the Uniform Linear Array (ULA), estimating the direction-of-arrival (DOA) of the sources as well as the mutual coupling coefficients of the array can be formulated as a linear inverse problem, where the solution is given by the Kronecker product of the vectors with respect to the DOAs and the mutual coupling coefficients. Through mathematical manipulation, these solution vectors can be decoupled. Estimation of the DOAs is cast into the framework of sparse solution finding. To derive the solution, an alternating minimization technique is presented. The proposed method is firstly developed based on the noise free observation covariance matrix, and can be generalized to directly using the snapshots. Using the proposed method, DOA estimation is feasible even in single snapshot case. The performance of the proposed methods with covariance matrix, single snapshot and multiple snapshots are illustrated by computer simulations. Their ability to resolve closely spaced targets and the applicability to correlated sources have also been demonstrated.

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.

This study includes three parts: First is fuzzy modeling of scattered field from unloaded dipole antenna. In second step a fuzzy model for scattered field from a linearly loaded thin dipole antenna is introduced. In both parts, knowledge bases of diameter and load impedance are separately extracted and saved as very simple curves. It is shown that the behavior of scattering dipole antenna is well approximated with the single transmitting dipole antenna obtained in our previous study. In the third step, using the concept of spatial membership functions, two obtained knowledge bases are combined so that the spatial knowledge base including simultaneous effects of diameter and load impedance is extracted. As a result, these spatial knowledge base as well as the behavior of single transmitting dipole antenna are used instead of time consuming and repetitive computations in accurate methods. With the use of this spatial knowledge and behavior of single transmitting dipole antenna, the scattered field from dipole antenna for any load impedance and diameter is predicted. Comparing the predicted results with accurate ones shows an excellent agreement. Moreover the computation time is considerably reduced.

The electrodynamical rigorous solution of Maxwell's equations related to the microwave pulse propagation inside a threedimension heart model is presented here. The boundary problem was solved by using the singular integral equations' method. The carrier microwave frequency is 2.45 GHz. The pulse durations were always equal to 20 ms. The modulating signals are triangular video pulses with the on-off time ratio equal to 5 and 100. The model heart was limited by a non-coordinate shape surface and it consisted of two different size cavities. The heart cavities were schematic images of the left and right atriums and ventricles. In our calculations the cavities were filled with blood with the permittivity ε₂ = 58 − i19 and the walls of the heart consisted of myocardium tissue with the permittivity ε₁ = 55 − i17. Microwave electric field distributions were analysed at four longitudinal cross-sections of the heart model.

This paper links joint direction of arrival (DOA) and frequency estimation problem to the trilinear model and derives a novel blind joint angle and frequency estimation algorithm. The proposed algorithm has better performance than ESPRIT algorithm. Our proposed algorithm is thought of as a generalization of ESPRIT. The useful behavior of the proposed algorithm is verified by simulations.

Based upon developed radial FDTD-method, used for solution of Maxwell equations in cylindrical coordinates and implemented in Matlab-7.0 environment, we simulated focusing of the annular Gaussian beam with radial polarization by conical microaxicon with numerical aperture 0.60. It is shown that the area of focal spot (defined as area where intensity exceeds half of its maximum) can be 0.096λ², and focal spot diameter equals to 0.35λ.

A He's Energy balance method (EBM) is used to calculate the periodic solutions of nonlinear oscillators with fractional potential. Some examples are given to illustrate the effectiveness and convenience of the method. We find this EBM works very well for the whole range of initial amplitudes, and the excellent agreement of the approximate frequencies and periodic solutions with the Exact or other analytical solutions has been demonstrated and discussed. Comparison of the result obtained using this method with that obtained by Exact or other analytical solutions reveal that the EBM is very effective and convenient and can therefore be found widely applicable in engineering and other science.

In this paper,a novel compact monopole ultra-wideband (UWB) antenna with a notched ground is presented. To increase the impedance bandwidth,a notched ground is introduced. The parameters and the characteristics of the antenna are given. It shows good characteristics for UWB,and it satisfies the VSWR requirement of less than 2.0 in the frequency band from 2.55 GHz to more than 13 GHz. The measured radiation patterns show good omnidirectional performance and antenna gains across the operation bandwidth.

The speedy dissemination of digital consumer electronics devices within personal area causes increments of multimedia communication and advent of entertainment networking. This feature of communication requires high data-rate transmission. In order to meet the demand, in this paper, we apply multiple antenna schemes to MB-OFDM UWB system. And to use the UWB system with multiple antennas for various channel environment, some adaptive MIMO schemes are considered for multiple antenna MB-OFDM system. The first investigated technique is adaptive antenna selection which selects the proper number of transmitting antennas using estimated SNR. And the second technique is adaptive modulation which can be used after the adaptive antenna selection is executed. By using these adaptive techniques, the reliable and high data-rate communications which are well adapted to the various user's demands and channel conditions are achieved.

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.