In this paper, a novel circular slot UWB antenna with dual notched frequency band is presented and investigated. A C-shaped slot is inserted into the fed element, and a parasitic strip is printed in the circular slot, so that the proposed antenna achieves dual band-notched characteristics, respectively. The measured and simulated results show that the proposed antenna meets the requirement of wide working bandwidth of 3.1-10.6 GHz with VSWR < 2, while avoiding the interference with the 3.5 GHz WiMAX and 5.5 GHz WLAN band. Study of transfer function (amplitude of S₂₁/group delay) and time domain characteristic (radiated pulses/power spectrum density (PSD)) correspond well with the VSWR, which indicate the dual band notched characteristic of the antenna.

This paper presents study of controllable leaky wave modes in various planar transmission lines operating at millimetre wavelengths. Leaky wave regime is achieved by exploitation of periodic inclusions. The main goal is to obtain the scanning of the radiation angle from forward to backward direction and rather broad range of scanning angles at a given operation frequency corresponding to the mm-wave range. For this purpose we suggest to use MEMS capacitors combined with shunt strap inductors, probably grounded. This design solution allows one to significantly reduce the losses in the loaded line compared to known scanning leaky-wave antennas based on varactors or on magnetized ferrites. The design of the unit cell is done using global optimization method, and the dispersion is investigated analytically. After analytical modeling and optimization, full wave analysis is done using Ansoft HFSS v.11 environment. After the leaky wave regimes are verified, an example of a leaky-wave antenna is introduced in order to confirm possibility of beam scanning.

A non-resonant microwave method has been proposed for accurate complex permittivity determination of low-loss materials. The method uses two measurement data of the magnitude of transmission properties of the sample. While the first datum must correspond to a frequency point resulting in a maximum magnitude of transmission properties, the other can be any datum at a frequency different than the first datum and not far distant from the first datum. Two closed-from expressions are derived for a good initial guess using the above data. The limitations of each expression are discussed. The method has been validated by transmission measurements at X-band (8.2-12.4 GHz) of a low-loss sample located into a waveguide sample holder.

A compact microstrip bandpass filter (BPF) with multispurious suppression is presented. The filter consists of two coupled half-wavelength stepped impedance resonators (SIRs) and tapped input/output (I/O) lines. With tuning the impedance ratio (K) and length ratio (α) of SIRs, a very wide stopband can be easily achieved. The filter is designed at 2.4 GHz (f₀) with a wide stopband to 20 GHz (8.16f₀) and an average rejection level better than 25 dB. This study provides a simple and effective method to achieve a filter with very wide stopband and compact circuit size simultaneously. Good agreement between the full-wave electromagnetic (EM) simulation and measurement is compared.

In this paper, extending the design technique presented by the authors in a previous work, we propose the study of a new family of polygonal patch antennas for portable devices of communication systems. Such antennas are suitable to be mounted in modern terminals, enabling wideband/multi-frequency operation and new multimedia features. The desired electromagnetic behaviour of the proposed radiators is obtained by adding either shorting posts, properly located between the polygonal patch and the ground plane, or circular slots, drilled at the appropriate position on the patch surface. Circular slots are also useful to easily accommodate a photo-camera in the terminal, in order to enable multimedia services and video calls. Some practical layouts of polygonal patch antennas to be used in: a) modern PDAs and Smart Phones integrating cellular phone operation and wireless functionalities; b) UMTS terminals integrating also GSM functionalities, are, finally, presented. The effectiveness of the proposed designs is confirmed through proper full-wave numerical simulations.

A novel type of wideband SICC filter using TM₀₁ mode coupling by the circular hole between the SICCs is proposed. Of circular symmetry, the TM₀₁ mode in SICC demonstrates the advantages of compact and high flexibility of the filter's input and output setting. In order to validate the new proposed topology, three filter prototypes with different included angle between input and output have been designed and manufactured. The filters exhibit a low insertion loss of -1 dB in the 12.8 to 20 GHz, a wide relative bandwidth of 54.5% at -3 dB, high flexibility and very good agreement with simulation data.

In this paper a new method is proposed to achieve a temperature insensitive, broad and flat gain C-band erbium-doped fiber amplifier (EDFA) with aid of macro-bending. This gain flattened C-band EDFA is demonstrated by utilizing 2.5 m macro-bent Erbium-doped fiber (EDF) at room temperature of 25℃. Further to this, it is shown that gain fluctuation at different temperatures is compensated in the proposed design. The EDFA performance at different temperatures is investigated for various macro-bending diameter and EDF length. The gain saturation and energy transfer from shorter wavelengths to longer wavelengths can be controlled by varying the bending radius and the length of the doped fiber, consequently, a flattened and broadened gain profile in the C-band region can be achieved. The amplifier uses a 2.5 m long EDF with 2000 ppm concentration and bending radius of 6.5 mm as a gain medium. The gain variation of the EDFA is obtained within ±0.5 dB over 35 nm bandwidth of C-band region.

Explicit Green's tensors for the diffusive electric field in a configuration with two homogeneous half spaces are of interest for primary-secondary formulations of frequency domain and time domain modeling schemes. We derive the explicit expressions for the Green tensor of the electric field generated by an electric dipole in space frequency and space time. Both source and receiver can have arbitrary positions in the vertical transverse isotropic (VTI) half space below a non conductive half space. Apart from their use in modeling schemes, the expressions can be used to understand the effect of the interface between the VTI and the non conducting half space. We show that the TE-mode refracts against the interface, and its effect in the VTI half space decays exponentially as a function of depth and is inversely proportional to horizontal distance cubed for horizontal source receiver distances larger than three times the source depth. In exploration geophysics, this part of the field is known as the "airwave". The contribution from the "airwave" has a late time behavior that differs from the other contributions to the electric field. This makes time domain systems relevant for exploration geophysical applications.

The small-scale fading behavior in common wireless communication systems can be predicted by a series of propagation models. Although these types of models are feasible and effective for the situations of transmitting/receiving (Tx/Rx) antennas in relatively open surrounding environments, they are unable to address the coupling between the antenna and environment. In order to overcome this difficulty, a full-wave numerical method is applied in terms of the advantage in considering the interaction between complicated environments and the Tx/Rx antennas, and it can take into account the effect of the interaction on signals. In this paper, an integrative modeling technique involving FDTD method, two-path propagation model and multi-path statistical distribution model is presented, which combines the deterministic and statistical methods. For achieving reliable communication especially in high-speed railway environment, high sampling rate and adequate sampling points are needed for analyzing the propagation properties of the radio frequency (RF) link. This can be easily achieved by the integrative modeling technique, and the output voltage and current of train antenna under the illumination of base-station (BS) antenna along the railway can be given in detail. Results obtained from the integrative simulation for three different multi-path statistical distribution models are presented and analyzed.

An inverse equivalent surface current method working with equivalent electric and/or magnetic surface current densities on appropriately chosen Huygens surfaces is investigated. The considered model with triangular surface meshes is compatible with the models known from method of moments (MoM) solutions of surface integral equations. Divergence conforming current basis functions of order 0.5 and of order 1.5 are considered, where the order 0.5 functions are the well-known Rao-Wilton-Glisson basis functions. Known near-field samples typically obtained from measurements are mapped on the unknown equivalent surface current densities utilizing the radiation integrals of the currents as forward operator, where the measurement probe influence is formulated in a MoM like weighting integral. The evaluation of the forward operator is accelerated by adaptation of the multilevel fast multipole method (MLFMM) to the inverse formulation, where the MLFMM representation is the key to full probe correction by employing only the far-field patterns of the measurement probe antennas. The resulting fully probe corrected algorithm is very flexible and efficient, where it is found that the computation speed is mostly dependent on the MLFMM configuration of the problem and not that much on the particular equivalent current expansion as long as the expansion is able to represent the currents sufficiently well. Inverse current and far-field pattern results are shown for a variety of problems, where near-field samples obtained from simulations as well as from realistic measurements are considered.

Omni-directional antennas are useful for variety of wireless communication devices as well as capable of handling the additional different frequency bands since the radiation pattern allows good transmission and reception from a mobile unit. However, to implement the two frequencies on a single antenna with wide bandwidth can be significant because of the presence of mutual coupling and interference effects between the two radiating elements. In this paper, a novel method of combining dual-band frequencies onto a single layer board with wide bandwidth is described. A dual-band printed dipole antenna is designed in this study by combining a rectangular and two "L" shaped radiating elements and are embedded on a single layer structure with relatively small size. The obtained results show that the proposed dual-band omni-directional microstrip antenna achieves high antenna efficiency and provides better bandwidth while maintaining the structural compact size.

This paper presents a general analytical formulation for calculating the three-dimensional magnetic field distribution produced by Halbach structures with radial or axial polarization directions. Our model allows us to study tile permanent magnets of various magnetization directions and dimensions. The three magnetic field components are expressed in terms of analytical and semi-analytical parts using only one numerical integration. Consequently, the computational cost of our model is lower than 1 s for calculating the magnetic field in any point of space. All our expressions have been checked with previous analytical models published in the literature. Then, we present two optimized permanent magnet structures generating sinusoidal radial fields.

This paper studies the potential of ultra-wideband (UWB) microwave imaging for detection and localization of breast cancer in its early stages. A method is proposed for locating tumors which is based on the time-of-flight of the signal backscattered at the tumor. Time-of-flight is detected using a wavelet transform algorithm. The main contribution of this paper is that it proposes to determine the position of the tumor by using an adapted version of the centroid localization method used in wireless sensor nodes. Its main advantage is that it does not require knowing a priori neither the propagation velocity of the breast nor its dielectric permittivity. The feasibility of the method has been investigated by means of simulated and experimental results with an ultra-wideband radar and a phantom.

We numerically and experimentally evaluate different designs of coplanar waveguides (CPWs) loaded with split ring resonators (SRRs) and complementary split ring resonators (CSRRs), respectively. In particular, we are interested in their stop-band performance. Starting from structures which consist of two concentric rings, we study devices with only an outer ring, an inner ring or multiple concentric rings. Furthermore, our study shows that introducing slots in the proximity of the SRR or CSRR will modify the stop-band considerably. Single and multiple unit cells for both designs are fabricated and measured. Our results demonstrate the potential of the CSRR/CPW structure for filter applications.

The design of a flexible uniplanar AMC is presented. A prototype is manufactured and characterized based on reflection coe±cient phase under flat and bent conditions. The designed prototype shows broad AMC operation bandwidth and polarization angle independency in both flat and bent situations. Its angular margin when operating under oblique incidence is also tested. FEM simulations and measurements in an anechoic chamber are presented.

We apply the full-wave electromagnetic theory to study electromagnetic scattering by a small cylindrical particle with radial anisotropy for normally incident light with transverse magnetic (TM) polarization. The scattering coefficients are derived, when the radial anisotropies in both the permittivity and permeability tensors are taken into account. It is shown that the surface and volume plasmon resonances can be identified by the sign of dε_t/dq, in which ε_t is the permittivity element in a direction tangential to the local r-axis, and q is the size parameter. The near field distributions for surface and volume modes are illustrated by finite element method. It is found that small changes of anisotropy can affect the scattering efficiencies significantly. Moreover, the quadrupole and octupole resonant peaks may be much higher and sharper than those of dipole resonance in the scattering efficiency spectra.

This paper presents a comparative analysis between the experimental characterization and the numerical simulation results for a three-dimensional FCC photonic crystal (PhC) based on a self-assembly synthesis of monodispersive latex spheres. Specifically, experimental optical characterization, by means of reflectance measurements under variable angles over the lattice plane family [1,1,1], are compared to theoretical calculations based on the Finite Difference Time Domain (FDTD) method, in order to investigate the correlation between theoretical predictions and experimental data. The goal is to highlight the influence of crystal defects on the achieved performance.

Microwave Imaging (MI) has been widely investigated as a method to detect early stage breast cancer based on the dielectric contrast between normal and cancerous breast tissue at microwave frequencies. Furthermore, classification methods have been developed to differentiate between malignant and benign tumours. To successfully classify tumours using Ultra Wideband (UWB) radar, other features have to be examined other than simply the dielectric contrast between benign and malignant tumours, as contrast alone has been shown to be insuficient. In this context, previous studies have investigated the use of the Radar Target Signature (RTS) of tumours to give valuable information about the size, shape and surface texture. In this study, a novel classification method is examined, using Principal Component Analysis (PCA) to extract the most important tumour features from the RTS. Support Vector Machines (SVM) are then applied to the principal components as a method of classifying these tumours. Finally, several different classification architectures are compared. In this study the performance of classifiers is tested using a database of 352 tumour models, comprising four different sizes and shapes, using the cross validation method.

This paper presents the comparison results between two new generator configurations. These generator units are namely a field assisted switched reluctance generator (SRG) and a brushless dc (BLDC) generator. No permanent magnets are used in either unit. The field assisted SR generator consists of two magnetically dependent stator and rotor sets (layers), where each stator set includes twelve salient poles with windings wrapped around them, while the rotor comprises of eight salient poles without any winding or permanent magnet. There is a stationary reel, which has the field coil wrapped around it and is placed between the two-stator sets. The BLDC generator is also made up of two magnetically dependent stator and rotor sets, but each stator set includes nine salient poles with windings wrapped around them while, the rotor comprises of six salient poles without any windings or permanent magnets. There is also a stationary reel between the two layers to produce the magnetic field through the motor assembly. This magnetic field travels through a guide to the rotor then the stator and finally completes its path via the generator housing. The generator phase windings for each layer are connect such that all the stator poles in that set can have either north or south pole configuration while the stator poles in the other layer have the opposite pole arrangement. This type of connection can be used in motoring mode as well. To evaluate the performance of the generators, two types of analysis, namely, numerical technique and experimental study have been utilized. In the numerical analysis, three dimensional finite element analysis is employed, whereas in the experimental study, proto-types have been built and tested.

The appropriateness of dielectric loaded antenna for the passive millimeter wave imaging application has recently been demonstrated. In this paper, we analyze the optical performance of the passive millimeter wave (PMMW) imaging system based on a 1D focal plane array (FPA) of dielectric rod waveguide (DRW) antennas. A first step in the design process is to analyze the image quality potential of 1D FPA-based imaging system in terms of the point spread function (PSF) and the modulation transfer function (MTF). We consider the effect of lens, DRW antenna, electromagnetic crosstalk between adjacent DRW antenna elements in the array, and sampling. From simulation and measurement, we found that the image quality in the passive millimeter wave imaging system with a DRW antenna array is less sensitive to electromagnetic crosstalk between antenna elements in the array. The measurements and simulations show that the system is diffraction limited and also closely agrees with the Rayleigh criterion of resolution for diffraction limited optical systems.