A method of solving the scattering problem for general multilayer anisotropic structures composed of conventional materials and metamaterial is presented. The analysis is based on calculation of the hybrid matrix of layers by means of a recursive algorithm. The method does not have the complexity and instability problems of other methods and is reliable in all cases. The zero reflection from stratified structures of conventional materials and metamaterials has then been introduced Various aspects of such a structure from the viewpoints of frequency and incident angle are presented and a rule for zero reflection from anisotropic medium is addressed. An interesting special case of total transparency is observed.

In this paper, a novel broadband monopole antenna with an extended rectangular shaped slot based on coplanar waveguide (CPW)-fed is designed and presented. The antenna composed of a planar rectangular patch element embedded with a slots, capable of generating two separate resonant modes with good impedance matching. The parametric study is performed to understand the characteristics of the proposed antenna. To verify the simulated design concept, a prototype antenna is designed and fabricated on the FR4 substrate, and characterized experimentally. The overall size of the antenna is 35.24 mm×26.4 mm×1.6 mm including the finite ground CPW feeding mechanism and total volume of the antenna is 1.49 cm3. The antenna operates in broad frequency bands from 3.424 GHz to 6.274 GHz covering wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) bands. The maximum gain of the proposed antenna is 5.51 dBi at 4.78 GHz frequency band. The proposed antenna‟s radiation characteristics are also observed.

In this article a novel numerical technique, called Fitness Adaptive Differential Evolution (FiADE) for optimizing certain pre-defined antenna configuration to attain best possible radiation characteristics is presented. Differential Evolution (DE), inspired by the natural phenomenon of theory of evolution of life on earth, employs the similar computational steps as by any other Evolutionary Algorithm (EA). Scale Factor and Crossover Probability are two very important control parameter of DE .This article describes a very competitive yet very simple form of adaptation technique for tuning the scale factor, on the run, without any user intervention. The adaptation strategy is based on the fitness function value of individuals in DE population. The feasibility, efficiency and effectiveness of the proposed algorithm in the field of electromagnetism are examined over a set of well-known antenna configurations optimization problems. Comparison with the some very popular and powerful metaheuristics reflects the superiority of this simple parameter automation strategy in terms of accuracy, convergence speed, and robustness.

New dual-band bandpass filters with compact coupling and sizes reduction are proposed by using split ring stepped-impedance resonators and two paths coupling. In the new design, split ring SIR and defected ground structure are applied not only to reduce filter size but also to improve the filter performances. The presented filters have advantages of compact and novel structures, miniaturization and dual-band with nicer performances such as high selectivity, low passband insertion losses and so on, and these performances are demonstrated by measurement. The new design may be quite useful in wireless communication systems.

We present here the solution of the eigenvalue problems for the open metamaterial square and circular rod waveguides. The Maxwell's equations for the electrodynamical analsis of the open waveguides were solved by the Singular Integral Equations' (SIE) method and partial area method. Our SIE method is pretty universal and let us rigorously analyze open waveguides electrodynamically with any arbitrary cross-sections taking into account of the edge condition. The false roots did not occur applying the SIE method. The waveguide media can be of strongly lossy materials. The signs of the complex permittivity and permeability can be positive or negative in different combinations. We used our computer algorithms based on the two mentioned methods with 3D graphical visualization in the MATLAB language. We present here our numerical calculations of the metamaterial square waveguide with sides equal to 5×10^-3m and the metamaterial circular waveguide with the diameter equal to 5×10^-3m. We present dependences of phase constant and attenuation constant of metamaterial waveguides at the frequency range from 75 GHz till 115 GHz. We have compared the three dimension (3D) electric field distributions of the main mode and the first higher mode propagating in the square and circular metamaterial waveguides. The calculations of the electric fields were fulfilled at approximately 10000 points in every cross-section. We discovered that the electric field is concentrated at the waveguide boundary. The distribution of the electric field along the perimeter of the waveguide is not uniform. There are two areas on the perimeter of the square and circular waveguides where the electric field has maximum values. These areas are shifted relative to each other on π radians.

In this paper, the surface states (or so called Tamm states) of a nonlinear self-focusing slab sandwiched between a uniform medium and a one-dimensional photonic crystal has been investigated based on the first integral of nonlinear Helmholtz wave equation. The consider slabs can be a left-handed metamaterial or a conventional material. It is shown that the structure can support the Tamm states with two different transverse electric structure. In one kind, the surface waves has a hump at the surface of photonic crystal, and the other one has two humps. We reveal that in the case of self-focusing left-handed metamaterial slab, there is possibility for change of total flow's direction of surface waves by adjusting of the intensity of exciting electromagnetic field.

With the advent of DVB-T in most European countries, the European Union has decided to end all analogue television broadcasts in its member countries until 2012. This analogue switch-off, as well as the increased spectral efficiency of the DVB-T protocol will create a surplus of spectrum in the UHF band, part of which is to be used by mobile communications systems. In order for this "digital dividend" to be shared efficiently, the coexistence and interference parameters between DVB-T and other services (designated as IMT-Advanced by the International Telecommunications Union) have to be studied. In this paper a generic 5 MHz interfering signal is broadcasted in close proximity to a stationary DVB-T receiver. Various DVB-T parameters are then measured and analyzed for different frequency values and power levels of the interfering signal.

New cross-coupled bandpass filters using half-wavelength (λ/2) and branch-line resonators are proposed. The branch-line resonators are made of two quarter-wavelength (λ/4) resonators in which a shorted circuit is realized by one open stub. In the first case, a non-0°feed structure at the input and output resonators is used to produce one pair of transmission zeros near the passband to improve the selectivity. In the second case, good selectivity and improved stopband rejection can be achieved at the same time by utilizing a 0° feed structure. Specifically, the proposed filters can simplify the manufacturing process of the conventional cross-coupled filters using λ/2 and λ/4 resonators without increasing circuit area significantly.

During the past decades there has been a tremendous increase throughout the scientific community for developing methods of understanding human brain functionality, as diagnosis and treatment of diseases and malfunctions, could be effectively developed through understanding of how the brain works. In parallel, research effort is driven on minimizing drawbacks of existing imaging techniques including potential risks from radiation and invasive attributes of the imaging methodologies. Towards that direction a new near field radiometry imaging system has been theoretically studied, developed and experimentally tested and all of the aforementioned research phases are herein presented. The system operation principle is based on the fact that human tissues emit chaotic thermal type radiation at temperatures above the absolute zero. Using a phase shifted antenna array system, spatial resolution, detection depth and sensitivity are increased. Combining previous research results, as well as new findings, the capabilities of the constructed system, as well as the possibility of using it as a complementary method for brain imaging are discussed in this paper.

In this paper, a study on the dual-frequency box-shaped antenna is presented. With a 5-branch feeding strip and two plates of shorting strips, the antenna shows broadband and compact property. Then a U-shaped slot is etched for dual-band operation. Simulated and measured results all show that this antenna exhibits dual-wideband characteristic, covering several present wireless communication systems, such as GSM800/900 (824--960 MHz), WLAN11b (2.4--2.5 GHz), WiMax802.16 (2.5--2.7 GHz), and Bluetooth band (2.4--2.8 GHz). The simulated impedance bandwidth (2:1 VSWR) is 21.5% and 37.2% in the lower and higher band, ranging from 790MHz-980MHz and 2.3 GHz--3.35 GHz. Then details of the antenna are described and the prototype is fabricated and tested. A measured bandwidth of 19.8% and 38.9% in the two bands, ranging from 820 MHz--1000 MHz and 2.28 GHz--3.38 GHz, is observed, shown good agreement with simulated results. Moreover, the antenna has a coaxial feed with a compact size of 0.27λ×0.22λ×0.036λ (λ is the wavelength referenced to the lowest edge of the operating band 820 MHz).

Automated and accurate classification of magnetic resonance (MR) brain images is an integral component of the analysis and interpretation of neuroimaging. Many different and innovative methods have been proposed to improve upon this technology. In this study, we presented a forward neural network (FNN) based method to classify a given MR brain image as normal or abnormal. This method first employs a wavelet transform to extract features from images, and then applies the technique of principle component analysis (PCA) to reduce the dimensions of features. The reduced features are sent to an FNN, and these parameters are optimized via adaptive chaotic particle swarm optimization (ACPSO). K-fold stratified cross validation was used to enhance generalization. We applied the proposed method on 160 images (20 normal, 140 abnormal), and found that the classification accuracy is as high as 98.75% while the computation time per image is only 0.0452s.

A novel method based on the hybrid volume-surface integral equation (VSIE) and the impedance matrix interpolation technique is presented for the fast analysis of microstrip antennas in frequency sweeps. A novel impedance matrix interpolation scheme is extended to the impedance matrix associated with VSIE, thus providing high accuracy, high efficiency, and large interpolation bandwidth for metal-dielectric composite problems. To demonstrate the effectiveness and accuracy of the proposed technique, numerical results for typical rectangular patch antennas and a broadband U-slot rectangular patch antenna are presented. Good agreement among the interpolation results, the exact method of moments (MoM) solutions, the finite element method (FEM) solutions, and measured data is observed over the bandwidth. The interpolation bandwidth is further investigated through a scattering problem. Numerical results show that high accuracy is obtainable within 10:1 bandwidth.

In this paper, the synthesis of sub-arrayed monopulse planar arrays providing an optimal sum pattern and best compromise difference patterns is addressed by means of an innovative clustering approach based on the Ant Colony Optimizer. Exploiting the similarity properties of optimal and independent sum and difference excitation sets, the problem is reformulated into a combinatorial one where the definition of the sub-array configuration is obtained through the search of a path within a weighted graph. Such a weighting strategy allows one to effectively sample the solution space avoiding bias towards sub-optimal solutions. The sub-array weight coefficients are then determined in an optimal way by exploiting the convexity of the problem at hand by means of a convex programming procedure. Representative results are reported to assess the effectiveness of the weighted global optimization and its advantages over previous implementations.

In this paper, an improved TRL (Thru-Reflect-Line) calibration method is presented. This method is based on ten-term error model of a two-port vector network analyzer(VNA) measurement system. Eight error terms induced by fixtures as well as two leakage errors are derived directly from the S parameters of the calibration standards measured from the coaxial reference plane without converting S parameters to T parameters. To validate our algorithm, a microstrip device with a via hole and a coplanar waveguide transmission line are fabricated and calibrated using the present TRL calibration method and Engen's algorithm, respectively. The magnitudes and phases of S₁₁ and S₂₁ of the devices are compared. The consistency of the de-embedded results with those calibrated by Engen's TRL algorithm illustrates the validity of the TRL algorithm in this paper.

An important aspect of the studies undertaken in bioelectromagnetism relates to the choice of the exposure facility, the characteristics of a real electromagnetic environment are far more complex compared to the one plane wave irradiation set-up used in the majority of bioelectromagnetic studies. Moreover biological requirements should represent the starting point in the design of an in vitro exposure system. Indeed it is important to avoid altering the electromagnetic properties of the exposure system in the presence of the biological equipments. Related to these two essential points, this article contributes to show the advantages of a Mode Stirred Reverberation Chamber (MSRC) to guarantee a controlled electromagnetic environment around biological material for in vitro experimentation. An example of irradiation of in vitro human skin cells cultures will be considered to illustrate this paper. In order to show that the biological conditions and physical requirements for in vitro experiments are checked, two aspects are described. Firstly the characterization of the electromagnetic field generated around the biological system (both equipments and cultures) is achieved. Secondly the analysis of the Specific Absorption Rate (SAR) inside the biological medium is evaluated both numerically and experimentally. Initially, the statistical properties of fields inside the MSRC were checked with or without biological devices in order to verify their electromagnetic transparency with respect to the reverberating properties of the electromagnetic environment (inside MSRC) and the good agreement of the experimental electromagnetic power distribution with the theoretical one. The second part of this work corresponds to the determination of the SAR distribution. The computation of electromagnetic energy absorbed by biological medium (SAR) was based upon Finite Difference in Time Domain (FDTD) technique. A numerical analogy was achieved between MSRC behavior and a free-space finite sum of random plane waves. Simulations are able to provide both an estimation of SAR distribution inside each biological culture dish and a computation of the coupling effects between dishes. Relying on the previous conclusions, temperature measurements were led to evaluate the experimental SAR levels and its time variations inside the MSRC. Two high-frequency (900 MHz) environments were considered: a 10 minutes exposure with standard field amplitude inside the biological incubator of 7.87 V/m and 30 minutes with 41V/m (SAR ranged from 2.6 mW/kg to 73 mW/kg, mean values). Numerical and experimental results prove the ability of MSRC to provide a large and efficient tool to achieve bioelectromagnetic experiments at high frequencies.

This paper presents the modified design that can reject harmonic components in the branch-line coupler. After adding open stubs at the center of branch lines of the traditional design, their new network parameters can be found in order to maintain the conventional function at an operating frequency and suppress its harmonic terms chosen. Experimental results show the second and third harmonic suppressions to be -28.3 and -39.6 dBs, while maintaining its traditional performance at the fundamental frequency.

To simulate imaging systems, Fourier optics has been applied very successfully to optics for decades. However, when simply moving to indoor millimeter wave imaging systems, some assumptions underlying the Fourier optics may break down, which contribute to the errors by applying Fourier optics. During the review of mathematical derivation of the Fourier optics, we point out how the errors are introduced by making the Fresnel approximation and omitting the phase factors. To distinguish from much literature, we discuss the accuracy of Fresnel approximation rather than plane wave. Moreover, we check the simulation results for millimeter wave imaging systems working in both pixel scanning mode and focal plane array mode and compare them to the results predicted by Fourier optics. It is shown that the difference can be 28% for the speckle contrast when the object is with certain roughness. The optical routine is that when the lens is four times'larger than the object, the imaging system can be considered as isoplanatic, thus Fourier optics can hold. Our simulation results imply that it may not be valid in indoor millimeter wave imaging systems. The goal of this paper is to draw some attention to the possibly large errors when modeling or designing the indoor millimeter wave imaging systems by Fourier optics directly. The mathematical discussions of the inaccuracies due to some approximations in Fourier optics can serve to understand and deal with aberrations.

Based on the vectorial angular spectrum representation and the method of stationary phase, internal vectorial structures of a phase-flipped Gauss (PFG) beam diffracting in the far field are derived in analytical forms. The energy flux for the TE term, TM term and the whole beam are derived and depicted by numerical examples. Influences of the f parameter on the whole energy flux distributions are analyzed. Discrepancies of the whole energy flux distributions between the paraxial and non-paraxial cases are shown in detailed manners. Furthermore, influences of the f parameter on discrepancies between two cases are also studied.

Recent research demonstrates that sparse beam pattern constraint can suppress the sidelobe level of the linear constraint minimum variance beamformer. Here we improve the standard beam pattern by replacing it with a combination of a total difference minimization constraint on the mainlobe and a standard C₁ norm minimization constraint on the sidelobe. As the new constraint matches the practical beam pattern better, the sidelobe level is further suppressed, while the robustness against the mismatch between the steering angle and the direction of arrival (DOA) of the desired signal, is maintained.

Scattering of electromagnetic (EM) waves by many small particles (bodies), embedded in a homogeneous medium, is studied. Physical properties of the particles are described by their boundary impedances. The limiting equation is obtained for the effective EM field in the limiting medium, in the limit a → 0, where a is the characteristic size of a particle and the number M(a) of the particles tends to infinity at a suitable rate. The proposed theory allows one to create a medium with a desirable spatially inhomogeneous permeability. The main new physical result is the explicit analytical formula for the permeability μ(x) of the limiting medium. While the initial medium has a constant permeability μ0, the limiting medium, obtained as a result of embedding many small particles with prescribed boundary impedances, has a non-homogeneous permeability which is expressed analytically in terms of the density of the distribution of the small particles and their boundary impedances. Therefore, a new physical phenomenon is predicted theoretically, namely, appearance of a spatially inhomogeneous permeability as a result of embedding of many small particles whose physical properties are described by their boundary impedances.