The earlier developed combined beam-absent analysis of the disc-loaded-coaxial waveguide in two-configurations (part-1) has shown promise for wideband gyro-traveling-wave tube (gyro-TWT) if the configurations are used as interaction structure. In the present paper, the beam-present dispersion relation and small-signal gain equation in Pierce's format for the disc-loaded-coaxial waveguide were developed. A broadening of the device bandwidth was presented by disc-loading the coaxial waveguide interaction structure of a gyro-TWT with a comparison against the circular cylindrical waveguide, coaxial waveguide, and disc-loaded circular waveguide in their respective gain-frequency responses obtained by using a numerical computer code on the basis of the present beam-present analysis.

The electromagnetic field analysis of the disc-loaded-coaxial waveguide in two configurations was developed in TE-mode for its potential application in the fast-wave regime using the field matching technique at the cylindrical interface between disc-free and disc-occupied structure regions. The space harmonics were considered for the axial periodicity and the azimuthal harmonics were ignored for azimuthal symmetry of the present configurations. The dispersion and azimuthal interaction impedance characteristics obtained by present analysis were validated against those obtained by simulation software --- HFSS within 0.1% and 0.5%, respectively. In special cases, the disc-loaded-coaxial structure reverts to well known conventional structures. The effect of structure parameters on the shape of dispersion characteristics was investigated in order to obtain a wideband-coalescence between the beam- and waveguide-mode dispersion characteristics, required for the wideband device performance, without deteriorating the impedance value.

Although there is no certain known mechanism of how the electromagnetic fields (EMFs) at power frequency (50/60 Hz) can affect human health, it has been epidemiologically shown that they have many hazards on human health. Also the power frequency fields may interfere with the nearby electrical and electronic equipment. In response to the precautionary principle, it might be needed in some situations to reduce the magnetic and electric fields of a high voltage line segment when it passes in close proximity to a populated area or may interfere with sensitive equipment. In other words, new arrangements of high voltage "green lines" are needed. This paper introduces a numerical solution based on Particle Swarm Optimization (PSO) technique, to reduce both magnetic and electric fields of high voltage overhead transmission line by rearranging the conductors. The horizontal, vertical, and triangular configurations of both single circuit and double circuit transmission lines were investigated. The examples presented in this paper show that the rearranged line configurations can introduce up to 81% reduction in magnetic field and up to 84% in electric field when the effects of ice and wind are considered, and up to 97% reduction in both magnetic and electric fields when these effects are neglected. A comparison is made between the cost of reducing EMFs of a line segment in a suburban area in Amman in Jordan, and the cost of not-reducing EMFs, where it is found that the cost of reducing the fields is outweighed by the "possible health costs" otherwise.

A probe-fed air-substrate patch antenna with an inclined radiating patch for generating a downtilt main beam for WLAN operation in an on-wall access point is presented. The proposed antenna has a simple structure and consists of two major parts: an L-shaped ground plane and an inclined radiating patch, which is easy to implement. Constructed prototypes suitable for operating in the 2.4 GHz WLAN band are demonstrated. Results indicate that, simply by varying the inclination angle of the radiating patch, a downtilt main beam with a wide range of downtilt angles can be achieved. In addition, by selecting the proper inclination angle of the radiating patch, the proposed antenna shows a narrower 3-dB beamwidth in the elevation plane, resulting in an enhanced antenna gain, which is very suitable for on-wall 2.4 GHz WLAN access point applications. Details of the proposed antenna design are described, and experimental and simulation results are presented.

The nucleation and growth of primary Al₂Cu phase in the Al-34.3wt%Cu hypereutectic alloy without and with a 12 T magnetic fields have been investigated by differential thermal analysis (DTA). The DTA curves indicated that the nucleation temperature of primary phase was significantly reduced in a magnetic field. The X-ray diffraction (XRD) patterns confirmed that the c-axes of primary Al₂Cu crystals oriented along the direction parallel to a magnetic field. The microstructures showed that primary crystals aligned along a magnetic field and that their number distinctly increased with increasing a magnetic field as well. The suppression of nucleation in a magnetic could be caused by the increase of the interfacial energy between the liquid and nucleus and the reduction of atom diffusion rates while the orientation of primary crystals were mainly attributed to both of the magnetic toque and the thermoelectric magnetohydrodynamic (TEMHD) flows.

This paper presents the graphics processing unit (GPU) accelerated fundamental alternating-direction-implicit finite-difference time-domain (FADI-FDTD) with complex frequency shifted convolutional perfectly matched layer (CFS-CPML). The compact matrix form of the conventional ADI-FDTD method with CFS-CPML is formulated into FADI-FDTD with its right-hand-sides free of matrix operators, resulting in simpler and more concise update equations. Using Compute Unified Device Architecture (CUDA), the FADI-FDTD with CFS-CPML is further incorporated into the GPU to exploit data parallelism. Numerical results show that a much higher efficiency gain of up to 15 times can be achieved.

In this paper, a three dimensional geometrical scattering channel model for indoor and outdoor wireless propagation environments is introduced. It is based on the assumption that the scatterers are distributed within a spheroid, in which the mobile station and base station are located at the spheroid's foci. This model captures both the spatial and temporal statistical distributions of the received multipath signals. Several angle of arrival and time of arrival probability density functions of the received multipath signals are provided in compact forms. The angle of arrival probability density functions are obtained in terms of both the azimuth and elevation angles. Numerical results are presented to illustrate and verify the derived expressions. To validate the model, it has been compared against some available two dimensional models and measured data.

Here we present the rigorous electrodynamical solution of microwave scattering by a multilayered electrically or (and) magnetically anisotropic circular cylinder. The number and thickness of layers may be arbitrary. We present the solution when all area of multilayered cylinder can be made of different uniaxial anisotropic or isotropic materials. The multilayered cylinder media can be of strongly lossy materials. The signs of the complex permittivity and permeability tensor components can be positive or negative in different combinations. Here we present the numerical dependencies of the Poynting vector radial component P_ρ that is responsible for the scattered and absorbed powers when the incident microwave impinges on the anisotropic Lithium Niobate (LiNbO₃) cylinder as well as on two single isotropic cylinders. The permittivity tensor components of the anisotropic cylinder are ε_t=43-i0.0005, ε_p=28-i0005 as well as for the isotropic cylinders the permittivities are ε_t=ε_p=43-i0.0005 and ε_t=ε_p=28-i0.0005. We show here the pattern of the value P_ρ inside and outside of the LiNbO₃ and two isotropic cylinders when the polar angle changes from 0 to 360 degrees with the step equal to one degree. We present here our calculations when the incident microwave has perpendicular or parallel polarization at three frequencies 65 GHz, 92.5 GHz and 120 GHz. We found that the values P_ρ for the anisotropic cylinder have the opposite behavior of dependencies on the permittivity tensor components for the incident microwaves of different polarizations.

A sleeve monopole antenna, which has a wide impedance bandwidth for indoor base station applications, is successfully realized experimentally and numerically. The proposed antenna consists of dual sleeves, loaded circular disc and two shorted pins which are connected to the circular ground plane. The antenna possesses 14-dB impedance bandwidths of 30.3% and 46.5% at the lower and higher bands, respectively. And the 10-dB return loss bandwidth of the antenna is 128.2%, which is about 48 times that of the traditional monopolar wire-patch antenna. The antenna is successfully simulated, designed, and measured, showing dual-band and wide band characteristics, stable gain and good omni-directional radiation patterns.

Terahertz spectroscopy brings precious complementary information in life science by probing directly low energy bindings inside matter. This property has been demonstrated on dehydrated substances, and interesting results are obtained on liquid solutions. The next step is the characterization of living cells. We have successfully integrated THz passive circuits inside Biological MicroElectroMechanical Systems (BioMEMS). They are based on metallic wires called Planar Goubau Line (PGL). We demonstrate that high THz measurement sensitivity can be reached with new design based on spirals. But we show that the principal interest of this design is its high spatial resolution below the wavelength size compatible with living cell investigation.

Integration of multiple functions is for the first time achieved within a single patch element. Firstly, out of phase equal power division and bandpass filter characteristics are combined within a patch element. The novelty of the proposed structure is to use simple asymmetric cross slots in the patch element to achieve this integration. A simplified equivalent circuit model to describe operation of this patch element is proposed. Coplanar waveguide/microstrip broadside coupling is then investigated to enhance the performance of the patch balanced filter and eliminate narrow coupling gaps and microstrip lines. Subsequently, transition between microstrip and coplanar waveguide is then added to the patch element by using certain electromagnetic coupling methods for higher level integration without introducing additional loss. Different patch elements operating at 2.4 GHz are developed to validate the feasibility of the proposed structures. The circuits were designed, fabricated and measured. The measured results agree quite well with the simulation, exhibiting small amplitude and phase imbalance at the output ports throughout the desired passband, and good rejection levels elsewhere.

In this paper, a new technique is developed to evaluate efficiently the Sommerfeld integrals arising from the problem of a current element radiating over a lossy half-space. The annihilation of the asymptote and the branch-point singular behavior of the spectral Green's function is used in this technique. The contributions of the subtracted asymptotic and singularity terms are calculated analytically. The annihilation results in a remaining integral that is very smooth and can be calculated adaptively by using Gaussian quadratures and extrapolation methods to accelerate the convergence of the oscillating integrand. The accuracy and efficiency of the new technique has been confirmed by comparison with literature, and the commercial software NEC. The application of the proposed technique provides a robust and rapid procedure to calculate spatial Green's functions which can be used in ground-wave propagation, and lightning return stroke channel modeling.

Two microstrip fed ultra-wideband (UWB) antennas with different band rejection techniques are presented in this paper. The designed antennas consist of a defected ground plane with an elliptical slot and two different radiator shapes. The first design is composed of a half circular ring radiator element while the second one uses a crescent shaped radiator. The radiators are fed by a 50 Ω microstrip line with a tapered microstrip transition to ensure good impedance matching. The calculated impedance bandwidth of the proposed antenna ranges from 3 GHz to 14 GHz with relatively stable radiation patterns. To achieve band-notch characteristic in the 5.0--6.0 GHz WLAN frequency band, two different techniques have been implemented. The first technique uses a C-shaped slot etched in the ground plane while the other one uses another Cshaped slot in the feed line.

In this paper we present a new method for the design of multi-band microstrip filters. The proposed design method is based on Differential Evolution (DE) with strategy adaptation. This self-adaptive DE (SaDE) uses previous experience in both trial vector generation strategies and control parameter tuning. We apply this algorithm to two design cases of dual and tri-band filters for WiFi and WiMax applications. We select the Open Loop Ring Resonator (OLRR) filters, which are comprised of two uniform microstrip lines and pairs of open loops between them. The results indicate the advantages of this approach and the applicability of this design method.

The scattering of an oblique electromagnetic wave incident on a sub-wavelength circular pore with a finite depth on the surface of a semi-infinite perfect conductor is investigated analytically. We use the method of matched asymptotic expansion to find the multipole structure. The expansion is based on the duality property of the source-free Maxwell equations, and the resultant scattering fields are fully expressed in terms of the scalar and the conjugate vector potentials. There are two regions defined by the analytical method: the electro/magneto-static inner region and the radiation outer wave region. For both TM and TE incidences, the scattering waves are lead by leading dipoles. In the next order of the scattering waves, a mixture of the dipole, the quadrupole and the octupole is found. This is a striking finding, that the multipoles are not organized in a strictly ascending manner when the size of the pore is considered. In addition, the sophisticated three-dimensional interplay of the multipoles, the pore depth, and the incident angle is revealed. The magnitudes of the scattering dipoles are confirmed convergent smoothly to those of the back-scattering dipoles of electromagnetic waves transmitted through a hole in a perfect conducting plate with a finite thickness when the pore depth is larger than about 1, normalize to the pore radius.

The authors suggest the generalized method of induced electromotive forces (EMF) for the investigation of the characteristics of single and systems of thin impedance vibrators at their arbitrary excitation and distribution of the surface impedance on the ground of the made analysis in the pro-posed paper. The distinctive peculiarity of this method is the use of the approximating functions, re-sulted from the integral equation solution for the current by means of the asymptotic averaging me-thod, in the current distribution along the impedance vibrator.

A rectangular dielectric resonator antenna (DRA) based on Barium Strontium Titanate --- Cyclic Olefin Copolymer (BST-COC) composite for 2.4 GHz wrist application is designed and characterized. The dielectric properties of the composite with ~57 vol.% BST loading are characterized using microstrip ring resonator structures at 2.45 GHz frequency. The proposed DRA, fixed onto a reverse grounded FR4 laminate, has a very compact size of 19 mm×10 mm×5 mm. The impact of the user's body proximity on the radiation performance of the antenna is studied experimentally. The percentage total efficiency and gain of the antenna deteriorated by about 8.5% and 2 dB due to the proximity of the user's body. The proposed DRA showed better performance than that of resonant type of antennas when close to the user's body.

A non-resonant microwave method has been proposed for accurate and stable constitutive parameter measurement of low-loss dispersive and non-dispersive isotropic materials. The method uses transmission-only measurements of two configurations: a) the sample inside a sample holder and b) the sample backed by a reference sample inside the same holder. It is not prone to undesired ripples in the extracted constitutive parameters arising from measured similar reflection properties. In addition, its accuracy is higher since it is not much affected by surface roughness and/or unevenness of the sample or the reference sample. It is based on frequency-by-frequency extraction and thus suitable for dispersive materials. However, it requires the selection of an appropriate reference sample. The method has been validated by measurements at Xband (8.2--12.4 GHz) of a low-loss sample located into a waveguide sample holder.

Apertureless scanning near-field optical microscopy (A-SNOM) with a superlens is a novel nano-optical system for sub-wavelength imaging purposes. This study presents a quantitative model for analyzing the heterodyne signals obtained from an A-SNOM fitted with a superlens at various harmonics of the AFM tip vibration frequency. It is shown that the image resolution is determined not only by the tip radius, but also by the superlens transmission coefficient in the high evanescent wave vector K_x. Moreover, the analytical results show that the images acquired from the A-SNOM/superlens system are adversely affected by a signal contrast problem as a result of the noise generated by the tip-superlens interaction electric field. However, it is shown that this problem can be easily resolved using a background noise compensation method, thereby resulting in a significant improvement in the signal-to-background (S/B) ratio. The feasibility of utilizing the system for maskless nanolithography applications is discussed. It is shown that the A-SNOM/superlens system with the proposed noise compensation scheme yields a dramatic improvement in the signal intensity and S/B ratio compared to that of a conventional A-SNOM with a bare tip only.

Synthetic Aperture Radar (SAR) can obtain a two-dimensional image of the observed scene. However, the resolution of conventional SAR imaging algorithm based on Matched Filter (MF) theory is limited by the transmitted signal bandwidth and the antenna length. Compressed sensing (CS) is a new approach of sparse signals recovered beyond the Nyquist sampling constraints. In this paper, a high resolution imaging method is presented for SAR sparse targets reconstruction based on CS theory. It shows that the image of sparse targets can be reconstructed by solving a convex optimization problem based on L1 norm minimization with only a small number of SAR echo samples. This indicates the sample size of SAR echo can be considerably reduced by CS method. Super-resolution property and point-localization ability are demonstrated using simulated data. Numerical results show the presented CS method outperforms the conventional SAR algorithm based on MF even though small sample size of SAR echo is used in this method.