A wideband unidirectional antenna composed of a magneto-electric dipole with Γ-shaped feed is designed. Simulated and measured results are presented. It achieves an impedance bandwidth of 84% for VSWR ≤ 2 ranging from 2.05GHz to 5.05GHz, stable peak gain of around 5 dBi, unidirectional radiation patterns and low cross polarization over the whole operating band. It is sufficient for accommodating recent wireless communication services such as 3G, WiFi, WiMax, Bluetooth, WLAN and Zigbee, etc.

This paper presents an Extended Exact Transfer Function (EETF) algorithm for Bistatic Synthetic Aperture Radar (BiSAR) imaging of a Translational Invariant (TI) case. This algorithm adopts directly the 2D transfer function of monostatic SAR (MoSAR), instead of deriving a new one, by converting the BiSAR into an equivalent MoSAR. A new azimuth phase compensation function is constructed through exploiting this equivalency. Geometry distortion correction for BiSAR imaging result is considered in the proposed algorithm. In addition, the applying condition of the algorithm is also discussed. One desirable property of the proposed algorithm is that the computing flow and efficiency are the same as ETF algorithm for MoSAR. The effectiveness is validated by point target simulations with Tandem and forward-looking configuration.

Use of water with different molecular mobilities could affect drug dissolution of a dosage form and such profile of water might be modifiable using microwave. This study investigated the effects of microwave on water and its influences on dissolution of free drugs and drugs in calcium-crosslinked alginate beads using sulphanilamide and sulphamerazine as hydrophilic and hydrophobic model drugs respectively. The water was treated by microwave at 300 W or without pre-treatment. The drug dissolution, pH and molecule mobility profiles of untreated and microwave-treated water were examined. Microwave-treated water had higher pH and water molecule mobility. The latter was characterized by higher conductivity, lower molecular interaction and crystallinity profiles. The dissolution of hydrophilic and hydrophobic free or encapsulated drugs was enhanced using microwave-treated water due to its higher molecular mobility. The untreated water of the same pH as microwave-treated water did not enhance drug dissolution. The drug dissolution from beads was increased by higher water uptake leading to matrix erosion and pore formation using microwave-treated water and was not promoted by the formation of non-crosslinked hydrated alginic acid matrix in untreated water of lower pH. Microwave treatment of water increased water molecule mobility and can promote drug dissolution.

In this paper, we present a new electromagnetic modelling analysis based on the Analytical Spatial Method of Moments (AS-MoM) using roof-top basis functions and prove advantages of integrals' resolution in conjunction with technique that permit to reduce the number of unknowns in the MoM matrix and to minimize time and memory consumption. This technique takes into account the existence of TEM zones inside the structure and far from discontinuities. There, we represent the current under an exponential form to analyze wave's propagation inside the structure. The advantages of this contribution will be illustrated by numerical results.

This paper discusses the design and development of a FPGA-based chirp generator for high resolution Unmanned Aerial Vehicle (UAV) Synthetic Aperture Radar. The desired bandwidth of the chirp signal is 100 MHz (combination of I and Q channels) with a chirp rate of 5 MHz/μs. Two algorithms based on the Memory-based architecture and the Direct Digital Synthesizer (DDS) architecture are presented. The measurement results indicate that the DDS chirp generator is a preferred choice for high-resolution SAR application.

Biological effects due to whole-body radio-frequency exposure may be induced by core temperature elevation. According to the international safety guidelines/standards for human protection, the whole-body averaged specific absorption rate (WBA-SAR) is used as a metric. In order to understand the relationship between WBA-SAR and core temperature elevation, a theoretical solution or a closed formula for estimating core temperature elevation is essential. In the present study, we derived a formula for simply estimating core temperature elevation in humans and animals due to whole-body radio-frequency exposure. The core temperature elevation estimated with the formula is found to be in reasonable agreement with the computational results of finite-difference time-domain computation incorporated in anatomically-based models. Based on the formula, the WBA-SAR is found to be a good metric for estimating core temperature elevation. The main factors influencing the core temperature elevation are the perspiration rate and the body surface area-to-weight ratio.

A study of electromagnetic wave propagation in dense plasmas when the wave frequency is below the cut-off frequency is presented. A three-layer symmetric structure consisting of dense plasma nested between two boundary layers is studied analytically and numerically. The permittivity of the dense plasma is negative, while the permittivity of each boundary layer is greater than 1. It is shown that total transmission of an electromagnetic wave can be achieved if an adequate incidence angle, dielectric permittivity of the boundary layers and corresponding boundary layer widths are chosen. It is found that plasma transparency is due to resonance between the evanescent waves in the dense plasma region and the standing waves in the boundary layers. Resonance conditions are derived analytically and the relationship between the corresponding parameters of the problem are studied numerically.

In this paper, electromagnetic scattering of a plane wave by large inhomogeneous arbitrarily shaped bi-anisotropic objects is solved by Adaptive Integral Method (AIM). Based on Maxwell equations and constitutive relationship for general bi-anisotropic media and using Volume Integral Equations (VIE), the electromagnetic fields are derived as functions of equivalent volume sources. Then the integral equations are discretized using Method of Moments (MoM). Because of the dense matrix property, MoM cannot be used to solve electromagnetic scattering by large objects. Therefore, AIM is adopted to reduce the memory requirement and speed up the solution process. Comparison between AIM and MoM with respect to CPU time and memory requirement is done to show the efficiency of AIM in solving electromagnetic scattering by large objects. Numerical results are obtained for some canonical cases and compared with Mie theory, in which excellent agreement is observed. some new numerical results are also presented for the more general bi-anisotropic material media.

Ultra Wideband (UWB) radar is a promising emerging technology for breast cancer detection based on the dielectric contrast between normal and tumour tissues at microwave frequencies. One of the most important considerations in developing a UWB imaging system is the configuration of the antenna array. Two specfic configurations are currently under investigation, planar and cylindrical. The planar configuration involves placing a conformal array of antennas on the naturally attened breast with the patient lying in the supine position. Conversely, the circular configuration involves the patient lying in the prone position, with the breast surrounded by a circular array of antennas. In order to effectively test the two antenna configurations, two 2D Finite-Difference Time-Domain (FDTD) models of the breast are created, and are used to simulate backscattered signals generated when the breast is illuminated by UWB pulses. The backscattered signals recorded from each antenna configuration are passed through a UWB beamformer and images of the backscattered energy are created. The performance of each imaging approach is evaluated by both quantitative methods and visual inspection, for a number of test conditions. System performance as a function of number of antennas, variation in tissue properties, and tumour location are examined.

The Radio Frequency Identification (RFID) applications are growing rapidly, especially in the UHF frequency band that is being used in inventory management. Passive UHF tags are preferred for these applications. In this paper, RFID reader-to-reader interference is analyzed. A model to estimate the minimum distance between readers to achieve a desired probability of detection in real multipath environments is derived and compared to the ideal case (AWGN channel). Diversity techniques to combat multipath and interference effects are proposed and studied.

The aim of this paper is to show the interest of using equivalence models for calculating the electric field produced by cylindrical capacitors with dielectrics. To do so, we use an equivalent model, based on the dual Maxwell's Equations for calculating the two electric field components created inside the capacitor and outside it. This equivalent model uses fictitious currents generating a electric vector potential that allows us to determine the electric field components in all points in space. The electric field produced by charge distributions as capacitor with dielectrics is generally determined by using the coulombian model. Indeed, it is well known that the electric field derives from a scalar potential. By using the Maxwell's equations, this scalar potential is in fact linked to the existence of charge distributions that are generally located on the faces of the capacitors. However, this last model does not allow us to obtain reduced analytical expressions since it involves the calculation of charge volume density appearing in the dielectric material for arcshaped cylindrical topologies. Consequently, it is interesting to look for another approach that gives analytical expressions with a lower computational cost. In this paper, we show that the use of fictitious currents instead of charges allow us to obtain 3D analytical reduced expressions with a lower computational cost. This analytical approach is compared to the coulombian model for showing the equivalence between the two approaches.

A novel compact balun (balanced-to-unbalanced) that consists of a low-pass network served by a microstrip electromagnetic bandgap (EBG) cell and a high-pass π-network formed with an interdigital capacitor is presented. This proposed approach can effectively operate the compact balun without the use of λ/4 microstrip lines to reduce the circuit area over 50% compared to the conventional Marchand balun. The core dimension of the compact balun is 0.74 cm x 0.7 cm. The planar structure enables an efficient circuit design in printed circuit boards (PCB) without using any bonding wires, defected ground structures (DGS), or surface mounted devices (SMD). A compact balun operating in the 3 GHz band has been implemented in a FR-4 PCB. From the measured results, the return loss of the input port is better than 15 dB over the band from 2.6 to 4 GHz. The amplitude and phase imbalances are less than 1.4 dB and 3° with the 20% operational bandwidth ranging from 2.7 to 3.3 GHz, respectively.

A novel dielectric cylindrical electronic bandgap antenna is presented and analysed using an in-house developed Finite-Difference-Time-Domain software simulator. The design steps and the simulations results of a geometrical parametric study are also presented and discussed, focusing on the design of antennas to operate in the X-band with high directivity patterns on the H-plane. Finally, the measurements results of a set of experiments carried out on a prototype showed very good agreement with simulations: 11% fractional bandwidth at 10 GHz and an average gain of 9.5 dBi are achieved in the impedance bandwidth with 13 dB front-to-back-ratio in the azimuthal plane.

Two closed form approximations are given for mutual coupling between arbitrarily oriented slots with cosinusoidal distribution, using the known results for dipoles along with a new correction factor to account for the piecewise sinusoidal dipole current. Using these approximations, a scheme has been developed for calculating mutual coupling between practically used slots of arbitrary orientation and useful results are obtained from simple closed form expressions for slot separation of 1.2 × slot length or more depending upon the approximation chosen and the length of the slot. These approximations are found to be more accurate than those available in the literature, with a maximum error of less than 1.6% for slots shorter than 0.5 wavelength and separated by 0.85 × wavelength or more. Simple yet accurate expressions for mutual coupling, like the point dipole approximation developed here, result in efficient evaluation of mutual coupling for the design of large arrays of slots or for Electromagnetic Compatibility analysis.

A down-link CATV/fiber-to-the-home (FTTH) and up-link FTTH transport system employing a reflective semiconductor optical amplifier (RSOA) as wavelength reuse and remodulation schemes is proposed and experimentally demonstrated. By using -1 side mode injection-locked/optoelectronic feedback techniques, brilliant performances of carrier-to-noise ratio (CNR), composite second-order (CSO), composite triple beat (CTB), and bit error rate (BER) were obtained for down-link transmission; low BER value was also achieved for up-link transmission over a 50-km single-mode fiber (SMF) transmission. Such a CATV/FTTH transport system is suitable for broadband access fiber networks.

This paper presents comprehensive methods for the design of a 900-MHz CMOS transmit/receive (T/R) switch with high power-handling capability. Techniques such as RF floated body to extend the bandwidth and decrease the insertion loss, and stacking architecture with high substrate isolation to enhance the power-handling capability are used for the design of a T/R switch on a standard 0.18um triple-well CMOS process. The measured performance of the T/R switch demonstrates the effectiveness of the methods presented in this paper such that insertion loss less than 1.0 dB, isolation up to 35.2 dB, and input 1-dB compression point of 30-dBm can be achieved at 900-MHz.

Flat left-handed metamaterial (LHM) lens can generate appropriate focusing spot in biological tissue as required in microwave tumor hyperthermia treatment. By using single flat LHM lens to concentrate microwave in a mass of tissue covered by water bolus, microwave hyperthermia scheme is proposed for superficial tumor hyperthermia. The power distribution in tissue is simulated by finite-difference time-domain method, and the thermal pattern is calculated by solving the bio-heat transfer equation. It is demonstrated that, by using a flat LHM lens of thickness of 4 cm to concentrate microwave of 2.45 GHz, a temperature above 42^oC can be achieved and maintained in one hour in a tissue region of about 1.0 cm in width and 1.2 cm in depth in tissue with the source amplitude of 43.40 V/cm, which is suitable for superficial tumor hyperthermia. By adjusting the position of microwave source, the heating zone in tissue can be adjusted in both the lateral and depth direction in tissue. The effects of fat layer and water bolus on the performance of hyperthermia are investigated as well.

This paper deals with the experimental validation of an effective near-field-far-field transformation technique with helicoidal scanning particularly suitable for electrically long antennas, whose validity has been numerically assessed in a previous authors' paper. Such a technique relies on the results relevant to the nonredundant sampling representations of the electromagnetic fields and makes use of an optimal sampling interpolation algorithm, which allows the reconstruction of the near-field data needed by the near-field-far-field transformation with cylindrical scan. The use of a prolate ellipsoid instead of a sphere to model an elongated antenna allows one to consider measurement cylinders with a diameter smaller than the antenna height, thus reducing the error related to the truncation of the scanning zone. Moreover, a significant reduction of the needed near-field data is also obtained. The comparison of the far-field patterns reconstructed from the acquired helicoidal measurements with those obtained from the data directly measured on the classical cylindrical grid assesses the effectiveness of the near-field-far-field transformation using this innovative scanning technique. At last, its validity is further confirmed by the very good agreement with the direct far-field measurements.

A numerical method is developed to calculate/simulate the separation of non-metallic inclusions from an aluminum melt by using a strong magnetic field (e.g., 10 Tesla) with high gradient generated via a superconducting magnet. The cases with and without imposed DC current on liquid aluminum in a cylindrical channel are discussed and compared. The migrating velocities of the non-metallic inclusions in an aluminum melt are calculated through force analysis and Navier-Stokes equations. In addition, the trajectories and removal efficiencies of the inclusions are evaluated. It is found that particle trajectories are influenced by the imposed flow rate and inclusion particle size. In addition, the removal efficiency is improved significantly, especially for small inclusions, e.g., <10 μm, by an imposed DC current on liquid aluminum in the high gradient area of a magnetic field.

In this paper, photonic bandgaps (PBGs) of the quasiperiodic structures is calculated using the Fourier transform of the refractive index profile. Comparing the reflectivity and Fourier spectrum of multilayer structure refractive index, we find that a peak in the Fourier spectrum is equivalent to a sinusoidal term in the refractive index. The wavelength of the peak location in the Fourier spectrum is half the wavelength where a PBG is located. Using Fourier transform analysis of the refractive index of any multilayer structure, we can determine the location of the PBGs of that structure. Peaks in the Fourier spectrum can be used to design reflective band optical filters in optical communication systems. The filtering wavelengths are twice the peaks in the Fourier spectrum.