A novel coplanar waveguide (CPW) fed wide tapered slot antenna (WTSA) is presented in this paper. A wideband CPW-to-wide slotline (WSL) transition is employed to feed the antenna. The corrugated edge structure and broken line tapered profile are also applied in this design to achieve wideband performance, as well as maintain compact size. A prototype of the antenna is fabricated. The measured results indicate that the antenna is a good candidate for UWB detection and imaging applications.

A new kind of field representation on the far field sphere is presented. This representation is based upon the polarisation states of the field. Polarisation states can easily be obtained upon determining the peculiar loci in the field. Depending on the polarisation state of the field, it is demonstrated that, either one of the magnetic or the electric dipole moments is dominant. Subsequently, criteria which may be applied to determine which dipole moment is responsible for the main radiation are derived. This characterization scheme which is a good figure of merit for an antenna designer may be useful in mobile communications especially in identifying possible adverse effects of RF fields on human health. The approach is also helpful for EMC engineers seeking to characterize and identify radiation sources of equipment under test.

A compact dual-band high impedance surface (HIS) electromagnetic band-gap (EBG) structure is designed as a reflector for a dual-band coplanar waveguide (CPW)-fed planar monopole antenna. The reflector comprises an array of metal square patches which are etched square ring slots. Details of the HIS structure and dual reflection phase frequency bands characteristics are presented and discussed. The simulated and measured results show that the combination of the HIS reflector and the antenna provides directional properties for both frequency bands. At the same time, compared to the antenna integrated with a metal reflector, the profile of the proposed antenna is reduced by more than 60%; the radiation efficiency is increased by 23% (simulated result); and the front-back ratio is increased by 17 dB and 11 dB at the two operating frequency bands, respectively.

This paper describes the application of two recently developed metaheuristic algorithms known as fire fly algorithm (FFA) and artificial bees colony (ABC) optimization for the design of linear array of isotropic sources. We present two examples: one for broad side arrays and the other for steerable linear arrays. Three instances are presented under each category consisting of different numbers of array elements and array pattern directions. The main objective of the work is to compute the radiation pattern with minimum side lobe level (SLL) for specified half power beam width (HPBW) and first null beam width (FNBW). HPBW and FNBW of a uniformly excited antenna array with similar size and main beam directions are chosen as the beam width constraints in each case. Algorithms are applied to determine the non-uniform excitation applied to each element. The effectiveness of the proposed algorithms for optimization of antenna problems is examined by all six sets of antenna configurations. Simulation results obtained in each case using both the algorithms are compared in a statistically significant way. Obtained results using fire fly algorithm shows better performances than that of artificial bees colony optimization technique provided that the same number of function evaluations has been considered for both the algorithms.

Miniature bandpass filter constructions based on a novel dual-mode suspended stripline resonator are proposed. Because of a special structure of the resonator, the frequencies of two first oscillation modes may be brought closer together. That allows realizing narrowband filters with the wide upper stopband. The filters have low insertion loss in the passband at small dimensions. Several transmission zeros substantially improve the filter performance. The derived coupling coefficients account for some features in the frequency response of the filter. The second-order and fourth-order filters with transmission zeros have been fabricated and measured.

Core loss data are usually provided in the form of tables or curves of total loss versus flux density or frequency for electrical machine designers. These tables or curves can be used to extract the loss coefficients of the core loss formulas because accurate calculations of the coefficients have an important issue in electrical machine design. In this study, using original loss data given for M19 steel material, the core loss coefficients are calculated by the genetic algorithm developed in Matlab environment and electromagnetic analysis software (Ansoft Maxwell) is also used to extract the core loss coefficients in order to verify the proposed method. It is found that the exponent of flux density (B) depends on the flux range or the frequency range and these changes in the exponent of B can be correlated to the physical phenomenon of domain wall movement in response to an external field. As a difference from existing studies in literature, this study suggests a new method for extracting the core loss coefficients without any requirement for mathematical operations due to the nature of genetic algorithms and over the range of frequencies between 50-400 Hz and flux densities from 0 to 1.5 T, the new method yields lower errors for the specific core losses than those obtained by the magnetic field analysis software.

Inverse Synthetic Aperture Radar (ISAR) imaging is one of the most sophisticated methods to obtain information about the scattering or radiation properties of a finite sized object. The idea is to process the scattered or radiated fields coherently over a certain frequency bandwidth and over a certain angular range in order to generate the image. In a simulation based approach, this procedure can be considerably simplified, if the source currents are known (either real or equivalent) and if a bistatic image is desired. By inserting the radiation integral into the imaging integral and by interchanging the integration orders, the imaging point spread function can be generated and the image formation is reduced to a convolution of the point spread function with the current distribution. A concise formulation of this well-known methodology is presented together with a discussion of important properties. Various examples of 2D and 3D images for complex metallic objects such as automobiles are shown, which have been obtained from the surface currents of a Shooting and Bouncing Rays (SBR) field solver.

We present an idea of grating-based plasmon biosensor utilizing phase detection to realize high resolution in finding a refractive index of a material put on the surface of a metal grating. Considering a trade-off between high resolution and experimental practicability, we show a table of recommended setup that covers a wide range of the index. Keeping the diffraction efficiency no less than 10^-3 and assuming the resolution in phase detection to be 2.5x10^-2 degrees, we estimate the resolution of the biosensor as 7.5x10^-7 refractive index units. We also discuss the possible improvement to realize a predicted superior limit of resolution around 10^-8.

Application to RCS computation of a higher order solver based on the surface integral approach is presented. The solver uses a direct method to solve the corresponding algebraic system of equations. Two versions of the solver are available: in-core and out-of-core. Both are efficiently implemented as parallel codes using Message Passing Interface libraries. Several benchmark structures are analyzed showing the reliability, performance, and versatility to run in a wide variety of computer platforms, of the solver. The results shown are illustrative of what is the maximum frequency of analysis of the structures for a given type of simulation platform.

Human body interaction is an important issue to take into account when designing handset antennas due to the effect that it has on the electromagnetic performance of the antenna. By means of electromagnetic simulation, three different antennas (a 1-meter length monopole and two small handset antennas) in three different situations (free-space, hand holding, and in pocket position) have been analysed at the FM band (88 MHz-108 MHz). Results prove that it is possible to predict the antenna behaviour in terms of quality factor (Q) by assessing the variations of the near electric field and the radiation efficiency in said environments. The estimated Q can be verified by calculating the Q using the input impedance. Results show that human body may improve the efficiency when the antennas become an extension of the human body.

This paper presents the investigations of nonreciprocal devices employing a novel ferrite coupled line junction. The structure is designed using coplanar line technology with the ground half-planes reduced to the strips. The investigated junction is composed of one ferrite section placed in between of two dielectric sections. In the ferrite section the longitudinally magnetized ferrite slab is located at the top or the bottom of the strips and is covered with the dielectric layers. In the dielectric sections the ports of the junctions are located. The wave parameters and field distributions of the modes propagated in the dielectric and ferrite sections are obtained from spectral domain approach. In order to determine the scattering matrix of the junction the mode matching method is utilized. The investigation of the circulator and isolator designed based on the S-matrix of the junction are presented. The obtained results are verified by comparing them with HFSS simulations and own measurements of the fabricated devices. In both cases a very good agreement is observed.

Breast Microwave Radar (BMR) has been proposed as an alternative modality for breast imaging. This technology forms a reflectivity map of the breast region by illuminating the scan area using ultra wide band microwave waveforms and recording the reflections from the breast structures. Nevertheless, BMR images require to be interpreted by an experienced practitioner since the location and density of the breast region can make the detection of malignant lesions a difficult task. In this paper, a novel bimodal breast imaging reconstruction method based on the use of BMR and Electrical Impedance Tomography (EIT) is proposed. This technique forms an estimate of the breast region impedance map using its corresponding BMR image. This estimate is used to initialize an EIT reconstruction method based on the monotonicity principle. The proposed method yielded promising results when applied to MRI-derived numeric breast phantoms.

Thin absorbing layers containing magnetic alloy or ferrite inclusions can be effectively used for attenuating common-mode currents on extended structures, such as power cords, cables, or edge-coupled microstrip lines. An analytical model to evaluate attenuation on the coaxial line with the central conductor coated with a magneto-dielectric layer is proposed and validated by the experiments and numerical modeling. The analytical model is validated using available magneto-dielectric samples of different thicknesses. This model can serve for comparing and predicting the absorptive properties of different samples of magneto-dielectric materials, whose compositions may be unknown, but dielectric and magnetic properties can be determined by independent measurements over the specified frequency ranges. From modeling the absorption in a coaxial line with a wrapped central conductor, it could be concluded whether it is reasonable to use this particular material in such applications as a shield on an Ethernet or other cable, for reducing potential common-mode currents and unwanted radiation in the frequency range of interest.

The dynamics of a system comprising of two bilaterally coupled Gunn oscillators (BCGOs) has been examined using a circuit theoretic model of the Gunn oscillator (GO). The effects of coupling factors (k_ij) between i-th and j-th oscillators on the frequency-range of synchronized operation and the magnitude of common frequency of oscillation have been examined semi-analytically and by numerical solution of the system equations. The occurrence of chaotic oscillations at the verge of synchronization bands is observed in numerical simulation. The experimental response of the BCGO operating in the X-band is obtained and the results are found to be qualitatively similar to the analytical and numerical predictions.

A novel and compact dual-mode defected ground structure (DGS) resonator is presented. Distinct characteristics of the proposed resonator are investigated. Using this type of resonator, a bandpass filter with the center frequency of 2.38 GHz and the fractional bandwidth of 6.7% is simulated and fabricated. The results show that this filter not only has an inherent transmission zero near the passband, but also has a very wide upper stopband with rejection better than 20 dB up to about 12 GHz.

To accurately model nanophotonic structures, a conformal dispersive finite difference time domain (FDTD) method based on an effective permittivity technique is presented, which can describe exactly the behaviors of evanescent waves in the vicinity of curved interface. A mismatch between the numerical permittivity and the analytical value introduced by the discretization in FDTD is demonstrated, thus, very fine time-step size is always necessary for nanostructures modelling, which greatly increases the required overheads of CPU time as compared to usual FDTD simulations. To resolve this problem, the performance of parallel FDTD code is investigated on a Gigabit Ethernet, and the acceleration technique for parallel FDTD algorithm is presented, which is developed by means of the replicating computation based on overlapping grids, the OpenMP multithreading technique and the vectorization based on SSE instruction. The comparison of relevant numerical results shows that these methods are able to reduce the expense of the system communications and enhance the utilization ratio of the CPU effectively, which improves greatly the performance of parallel FDTD with high time-consuming.

In this paper, modeling and experimentation of a Rectangular Patch Resonator (RPR) covered with a dielectric superstrate are investigated. The RPR criteria are established theoretically and experimentally, to be used in future prospects as an electromagnetic (EM) sensor for the characterization of superstrates. The theoretical model is based on the moment method (MoM) via Galerkin's approach, in which three types of basis and testing functions are used. These functions as well as the spectral dyadic Green function are efficiently implanted with compact structured Fortran 90 codes. The EM commercial HFSS and CST Microwave Studio softwares are used to simulate the proposed RPR prototypes. The accuracy of the obtained results is assessed using four prototypes of RPRs operating around 6 GHz, taking into account only the resonant frequency of the fundamental dominant mode. The theoretical model is compared to simulation and measurement results, and very good agreements are observed.

A Z-R relation is derived using a data set which consists of nine rain events selected from Singapore's drop size distribution. Rain events are separated into convective and stratiform types of rain using two methods: the Gamache-Houze method, a simple threshold technique, and the Atlas-Ulbrich method. In the Atlas-Ulbrich method, the variability of the rain integral parameters R, Z, N_w, D₀ and gamma model parameter $\mu $ are used for the classification of rain into convective, stratiform and transition. Z-R relations are derived for each type of rain after classification. The changes in the coefficients of the Z-R relations for different rain events are plotted and analyzed. The Z-R relations of the different methods using the Singapore data are compared and analyzed. It is concluded that the coefficient A of the Z-R relation is higher for the convective stage followed by the stratiform and transition stages. The coefficient b values are higher for the transition stage followed by the stratiform and convective stages. Reflectivities are extracted from RADAR data above NTU site for rain events and compared with the reflectivities derived from the distrometer data. Rain rates retrieved from RADAR data using the proposed relations from Singapore's data set are compared with the distrometer rain rates. The RADAR extracted rain rates are found to be constantly lower than the distrometer derived rain rates but matches well.

A novel Ultra Wideband (UWB) antenna on double substrates crossing is presented in this paper. Based on conical antenna and microstrip patch UWB antenna, the proposed antenna is omni-directional, band-notched and easy to be fabricated. It operates from 2.6 GHz to 12 GHz with low Voltage Standing Wave Ratio (VSWR<2), excluding a notch-band of 5.8 GHz. Except for good performance of VSWR, the proposed antenna keeps its radiating beam at about θ = 45°in E-plane through the whole band. The UWB antenna is fed by a coaxial probe through a SMA connector. The length of the proposed monopole element above the ground is slightly less than λ/4 of the lowest frequency. The simulated and measured results of the VSWR, he gain and the radiation patterns for the proposed antennas are presented and discussed. Good agreement between simulated and measured results is demonstrated.

A new three dimensional conical ground plane electromagnetic cloak is proposed and designed based on the coordinate transformation of Maxwell's equations. Material parameters of the conical invisible cloak are derived which have simple form and lesser inhomogeneity compared with other 3-dimensional cloaks. Because of convenient form of the constitutive tensors of the conical cloak, we propose a new strategy for homogeneous approximation of the materials of the cloaks. Numerical simulations confirm that approximation with eight slices, is more than enough and this cloak can hide any object on the ground as well as inhomogeneous ones.