The paper discusses fabrication of homogenous and heterogeneous breast phantoms to simulate the dielectric properties of human breast over the microwave frequency range from 0.5 GHz to 13.5 GHz. The breast phantoms have stable mechanical configuration and dielectric properties suitable for microwave imaging experiments particularly ultra-wideband microwave imaging for breast cancer detection.

The paper presents an analytical approach to treat the problem of transient oscillations in a cavity uniformly filled with nonstationary medium, which is characterized by time-varying permittivity and conductivity. Closed-form solutions are found for some transient excitations and medium parameters.

The anisotropic spherical Wigner-Seitz (WS) cell model --- introduced to describe colloidal plasmas --- is investigated using the linearized Poisson-Boltzmann (PB) equation. As an approximation, the surface potential of the spherical macroparicle expanded in terms of the monopole (q) and the dipole (p) is considered as an anisotropic boundary condition of the linear PB equation. Here, the "apparent" moments q and p are the moments 'seen' in the microion cloud, respectively. Based on a new physical concept, the momentneutrality, the potential around the macroparticle can be solvable analytically if the relationship between the actual moment and the "apparent" moment can be obtained according to the momentneutrality condition in addition to the usual electroneutrality. The calculated results of the potential show that there is an attractive region in the vicinity of macroparticle when the corresponding dipole part of the potential dominates over the monopole part, and there is an attractive region and a repulsive region at the same time, i.e., a potential well, when the corresponding dipole part of the potential just comes into play. It provides the possibility and the conditions of the appearance of periodic structure of the colloidal plasmas, although it is a result of a simple theoretical model.

In this paper, a novel dual-band rectangular slot antenna for wireless local area network (WLAN) applications in IEEE 802.11b/g/a systems is presented. The proposed antenna, fed by a 50Ω microstrip line, has size of 32 mm×28 mm×1.6 mm. By introducing a pair of U-shaped strips, the proposed antenna can generate two separate impedance bandwidths. The prototype of the proposed antenna has been successfully constructed and tested. The low-band resonant frequency is located at about 2.4 GHz, with -10 dB impedance bandwidth from about 2.3 to 2.5 GHz. The high-band resonant frequency is located at about 5.7 GHz, with -10 dB impedance bandwidth from about 4.9 to 6.0 GHz. In addition, the measured results show good radiation characteristics at the two operating bands, proving the dualband operation of the proposed antenna.

A new modification of the method of Mode Expansion in Time Domain is proposed for studying transient signals propagation in conical lines (including multi-connected ones) with inhomogeneous and time-dependent medium. The method is based on expanding the fields in spherical coordinate system into series of angular dependent modes with mode amplitudes being governed by a system of coupled evolutionary equations. The medium parameters (permittivity and permeability) are taken in a factorized form as a product of angular dependent factor and a factor that depends on time and radial coordinate. The introduced method can be applied to analysis of propagation and radiation in conical-like antennas with dielectric filling.

A multiresonance double cross element is used to design a dual-band reflectarray with dual linear polarization. The proposed element has a single conductive layer structure which makes it easy to manufacture. The results presented in this paper show that the mutual effect between the elements of the two bands is negligible. Hence, it is easy to achieve the phase compensation for each band separately. The simulated and measured results for an element designed to cover the X- and K-bands have confirmed the suitability of the proposed element to build a dual-band reflectarray.

This paper shows that L-shaped monopole antenna on PPS manufactured by inkjet printing of nano silver ink is able to produce very competitive overall antenna performance against Rogers copper foil structures if the thickness of the printed conductor layer is about the skin depth at the operating frequency multiplied by four.

We have investigated elliptical annular ring microstrip antennas having a sine wave periphery both theoretically and experimentally. The proposed antenna gives a good circular polarization at the center frequency of 1.296 GHz, with measured 3 dB axial ratio bandwidth of about 0.73% (9.5 MHz) and impedance bandwidth of about 1.7% (22.0 MHz). Input and radiation characteristics are also examined for different sine wave amplitudes applied to the periphery of elliptical ring patch antenna.

This work proposes the use of Non-Bianisotropic Split Ring Resonators (NB-SRRs) as building blocks for dual-band response filters. Design parameters will be evaluated in order to characterize coupling mechanisms for both the particle and filter structure. A ready-to-use dual-band filter for a multiconstellation Galileo/GPS global positioning receiver is manufactured in order to validate and test the proposed design. The device transmission response measurement agrees with both circuital and electromagnetic simulations, as well as with theoretical insertion losses, which are 2.4 dB and 3.5 dB at center passbands for L5 and L1 bands respectively.

Physical agents such as non-ionizing continuous-wave 2.45 GHz radiation may cause damage that alters cellular homeostasis and may trigger activation of the genes that encode heat shock proteins (HSP). We used Enzyme-Linked ImmunoSorbent Assay (ELI-SA) and immunohistochemistry to analyze the changes in levels of HSP-90 and its distribution in the brain of Sprague-Dawley rats, ninety minutes and twenty-four hours after acute (30 min) continuous exposure to 2.45 GHz radiation in a the Gigahertz Transverse Electromagnetic (GTEM cell). In addition, we studied further indicators of neuronal insult: dark neurons, chromatin condensation and nucleus fragmentation, which were observed under optical conventional or fluorescence microscopy after DAPI staining. The cellular distribution of protein HSP-90 in the brain increased with each corresponding (0.034 ± 3.10^-3, 0.069 ± 5.10^-3, 0.27 ± 21.10^-3 W/kg), in hypothalamic nuclei, limbic cortex and somatosensorial cortex after exposure to the radiation. At twenty-four hours post-irradiation, levels of HSP-90 protein remained high in all hypothalamic nuclei for all SARs, and in the parietal cortex, except the limbic system, HSP-90 levels were lower than in non-irradiated rats, almost half the levels in rats exposed to the highest power radiation. Non-apoptotic cellular nuclei and a some dark neurons were found ninety minutes and twenty-four hours after maximal SAR exposure. The results suggest that acute exposure to electromagnetic fields triggered an imbalance in anatomical HSP-90 levels but the anti-apoptotic mechanism is probably sufficient to compensate the non-ionizing stimulus. Further studies are required to determine the regional effects of chronic electromagnetic pollution on heat shock proteins and their involvement in neurological processes and neuronal damage.

Electromagnetic interference (EMI) has a negative effect upon the performance of circuit communication systems. The present study considers the case of EMI induced in a conducting wire, and derives equations to establish the effect of the EMI on a bistable multivibrator. The validity of the equations is verified experimentally. The results indicate that the degree of influence of the EMI on the bistable oscillator depends on the interference power, the interference frequency, the induced power, the output resistance of the circuit, and the parasitic capacitance. Moreover, it is shown that the harmonic noise increases with an increasing interference amplitude and frequency. The theoretical results are found to be in good agreement with the experimental data.

We propose a methodology --- based on linear embedding via Green's operators (LEGO) and the eigencurrent expansion method (EEM) --- for solving electromagnetic problems involving large 3-D structures comprised of N_D ≥ 1 bodies. In particular, we address the circumstance when the electromagnetic properties or the shape of one body differ from those of the others. In real-life structures such a situation may be either the result of a thoughtful design process or the unwanted outcome of fabrication tolerances. In order to assess the sensitivity of physical observables to localized deviations from the "ideal" structure, we follow a deterministic approach, i.e., we allow for a finite number of different realizations of one of the bodies. Then, for each realization we formulate the problem with LEGO and we employ the EEM to determine the contribution of the N_D - 1 "fixed" bodies. Since the latter has to be computed only once, the overall procedure is indeed efficient. As an example of application, we investigate the sensitivity of a 2-layer array of split-ring resonators with respect to the shape and the offset of one element in the array.

In this paper, a high performance diplexer is designed and fabricated for Global Positioning System (GPS) and wireless local area network (WLAN) applications simultaneously. The diplexer mainly comprises two dual-mode ring bandpass filters (BPFs), operated at 1.575 GHz and 2.4 GHz, respectively. By using the stepped-impedance resonator (SIR) in the BPFs, the size reduction and wide stopband from 2.8 GHz to 6 GHz are obtained. Moreover, several transmission zeros are located at the passband edges, thus improving the passband selectivity. Due to impedance matching between two BPFs, a high isolation greater than 40 dB between two channels is obtained. The diplexer is investigated numerically and experimentally. The simulated and measured results have a good agreement with the proposed design concept.

In this paper, the backscattering properties of a perfect electric conducting sphere coated with layered anisotropic media whose constitutive parameters are close to nihility are investigated. We show that the backscattering is more sensitive to the radial constitutive parameters than to the tangential ones. Compared with isotropic case, the anisotropic media with small axial parameters have the potential to yield more reduction of backscattering magnitude on coated perfectly conducting spheres.

The dispersion equation for electromagnetic waves guided by an open tape helix for the standard model of an infinitesimally thin and perfectly conducting tape is derived from an exact solution of a homogeneous boundary value problem for Maxwell's equations. A numerical analysis of the dispersion equation reveals that the tape current density component perpendicular to the winding direction does not affect the dispersion characteristics to any significant extent. In fact, there is a significant deviation from the dominant-mode sheath-helix dispersion curve only in the third allowed region and towards the end of the second allowed region. It may be concluded that the anisotropically conducting model of the tape helix that neglects the above transverse-current contribution is a good approximation to the isotropically conducting model that takes into account this contribution except at high frequencies even for wide tapes.

We derive van der Waals-London and Casimir forces by calculating the eigenmodes of the electromagnetic field interacting with two semi-infinite bodies (two halves of space) with parallel surfaces separated by distance d. We adopt simple models for metals and dielectrics, well-known in the elementary theory of dispersion. In the non-retarded (Coulomb) limit we get a d^-3-force (van der Waals-London force), arising from the zero-point energy (vacuum fluctuations) of the surface plasmon modes. When retardation is included we obtain a d^-4-(Casimir) force, arising from the zero-point energy of the surface plasmon-polariton modes (evanescent modes) for metals, and from propagating (polaritonic) modes for identical dielectrics. The same Casimir force is also obtained for "fixed surfaces" boundary conditions, irrespective of the pair of bodies. The approach is based on the equation of motion of the polarization and the electromagnetic potentials, which lead to coupled integral equations. These equations are solved, and their relevant eigenfrequencies branches are identified.

Ultra-Wide Band (UWB) technology is a new, useful and safe technology in the field of wireless body networks. This paper focuses on the feasibility of estimating vital signs --- specifically breathing rate and heartbeat frequency --- from the spectrum of recorded waveforms, using an impulse-radio (IR) UWB radar. To this end, an analytical model is developed to perform and interpret the spectral analysis. Both the harmonics and the intermodulation between respiration and heart signals are addressed. Simulations have been performed to demonstrate how they affect the detection of vital signs and also to analyze the influence of the pulse waveform. A filter to cancel out breathing harmonics is also proposed to improve heart rate detection. The results of the experiments are presented under different scenarios which demonstrate the accuracy of the proposed technique for determining respiration and heartbeat rates. It has been shown that an IR-UWB radar can meet the requirements of typical biomedical applications such as non-invasive heart and respiration rate monitoring.

An improved finite-difference time-domain (FDTD) method has been extended to analyze the antennas with complicated lumped/active networks in this paper. The improved FDTD method is based on a novel integral transform and the matrix theory. Combing the novel integral transform with Kirchhoff's circuit laws, the hybrid networks comprised of high order linear and nonlinear elements with arbitrary connection can be modeled by a stable matrix equation. An effective model is built for the linear lumped networks including the internal independent sources. A wire antenna loaded with wideband match network and a two-element active patch antenna loaded with Gunn diodes are analyzed by the developed techniques. The analysis results indicate that the improved matrix-type FDTD method is not only stable and accurate, but also time-saving in simulating the complicated hybrid networks.

A new efficient technique for the analysis of complex antenna around a scatterer is proposed in this paper, termed the iterative vector fields with uniform geometrical theory of diffraction (UTD) technique. The complex field vector components on the closed surface enclosing the antenna without platform are computed by higher order Method of Moments (MOM), and the scattered fields from the platform are calculated by UTD method. The process of iteration is implemented according to the equivalence theorem. Based on this approach, an approximation method is outlined, in which the computational time is saved largely, while the accuracy is not reduced. The relative patterns obtained from the present method and the approximation method both show good agreements with that obtained from MOM.

In this paper, some important concepts about the defected microstrip structure (DMS) and defected ground structure (DGS) interconnections are introduced. In concept number one, three different types of interconnections are analyzed for determining the unit length and frequency dependent characteristics, based on the perturbed direct and return current paths and electromagnetic (EM) simulations. Therefore, the proposed interconnections with nonuniform circuit and ground planes (DMS and DGS) can be modeled using the uniform circuit and ground planes with frequency dependent unit length parameters. This concept can be used for designing the microwave circuits loaded with DMS or DGS. Results show that the unit length parameters are the same at high frequencies but different at low frequencies due to the different current distributions and consequently different geometry shapes. In concept number two, the level of radiation in these interconnections due to the area of defects is determined and compared. The very large radiation, due to large etched area on ground plane, is a deficiency of DGS interconnections. Using the DMS version, the harmful radiation can be decreased effectively. In concept number three, the level of transition from passband to stopband is calculated and compared. Sharper transition can better suppress the band spurious signals. Finally, all performances are tabulated and compared.