The electromagnetic interface between the antenna and the human head is reduced with ferrite materials and metamaterials. The reduction of Specific Absorption Rate (SAR) with materials and metamaterials is performed by the finite-difference time-domain method with Lossy-Drude model by CST Microwave Studio. The metamaterials can be achieved by arranging split ring resonators (SRRs) periodically. The SAR value has been observed by varying the distances between head model to phone model, different widths, different thicknesses, and different heights of materials and metamaterial design. Materials have achieved 47.68% reduction of the initial SAR value while metamaterials achieved a reduction of 42.12%. These results can endow with supportive information in designing the wireless communications equipments for safety compliance.

This work focuses on microstrip patch antennas for the 77 GHz millimeter band. For some combinations of the parameters microstrip width, free wavelength and substrate permittivity, impedance matching via inset fed is found to be non applicable. The current distribution of the desired TM₁₀ mode is partially disturbed. Gap coupled parasitic microstrips are analyzed in order to match the feeding impedance to the feeding microstrip while improving the bandwidth in these particular cases.

An exact analytic solution is presented to the problem of scattering of a plane wave from a perfect electromagnetic conducting (PEMC) elliptic cylinder, using the method of separation of variables. The formulation is carried out by expanding the incident as well as the scattered electromagnetic fields in terms of appropriate angular and radial Mathieu functions and a set of expansion coefficients. The incident field expansion coefficients are known, but the scattered field expansion coefficients are unknown. Imposing the boundary conditions at the surface of the elliptic cylinder leads to the determination of the unknown expansion coefficients in closed form. Results are presented as normalized scattering widths for elliptic cylinders of different sizes and PEMC admittances, to show the effects of these on scattering.

In this article, a novel microstrip-line fed monopole dual band-notched antenna with tapered slot for UWB applications is presented. The tapered slot, making the antenna have a scissors-like shape, is taken into account to enhance the wideband characteristics. In addition, the dual notched bands, from 3.3 to 3.7 GHz and from 5.15 to 5.85 GHz, are achieved by inserting slots on the ground plane and adding circle arc stubs on the radiating patch. Details of the antenna design are described, a theoretical and experimental investigation of the antenna is given as well.

In this paper, reduction of peak specific absorption rate (SAR) for handsets with monopole type antenna through R-cards is investigated. While the numerical analysis was performed using finite integration in time domain (FIT), real measurement has been made to validate the simulation results. Both the simulation and measurement results revealed that a minimum SAR Reduction Factor (SRF) of 60% was achieved. The good agreement between the simulation and measurement results has evidenced the effectiveness of the proposed approach for SAR reduction in human head for handset applications.

The wide-angle bicone antenna terminated by a spherical cap is investigated. The antenna radiation patterns have been observed for various values of where represents the phase constant and represents the conical length. It is seen that for large values of the radiation pattern is limited within an angular sector bounded by the cones of the antenna. Next the antenna is optimized for ultra-wideband (UWB) operation through the use of loading techniques. The transient wideband radiated and received responses of the antenna have been observed and the relationship between the wave shapes of the transient field and the input pulse have been determined.

Microwave breast tumour detection is a non-invasive technique that uses non ionizing radiation. Microwave imaging has the potential to achieve early detection of breast cancer due to the high specificity and the large difference in electrical properties of the malignant tissue when compared to normal breast tissue. This paper studies the feasibility of using UWB signals for breast imaging. Simulated results using Finite-Difference Time-Domain (FDTD) Method will be presented. A sensibility study of the variations in the breast relative dielectric permittivity and of the variations of the skin-surface contour is also provided. A working prototype for microwave imaging is developed using a conventional Vector Network Analyzer (VNA) with the time processing capability.

In the present investigation, diffraction from a slit in perfectly electromagnetic conducting (PEMC) plane has been studied. Both the E- and H-polarization are considered and the method of analysis is Kobayashi Potential (KP). The mathematical formulation involves dual integral equations (DIEs). These DIEs are solved by using the discontinuous properties of Weber-Schafheitlin's integral. The resulting expressions, finally, reduce to matrix equations. These are then used to compute the values of unknown expansion coefficients. Numerical results are presented for different parameters of interest especially the dependance of co-polarized and cross-polarized components on the admittance parameter.

This paper addresses the design of fractal antennas placed onto dielectric object in the UHF RFID band and introduces a tag antenna configuration of simple geometry having impedance tuning capability. Through the paper, the dimensions of the fractal antenna are optimized to improve the impedance matching with the chip impedance. The tag performance changes are studied when it is placed on different objects (e.g., cardboard boxes with various content), or when other objects are present in the vicinity of the tagged object. It has been shown that a tag antenna can be designed or tuned for optimum performance on a particular object. Using the finite element method the open circuit voltage and the polarization mismatch factor against the operating frequency are calculated. The input impedance, reflection coefficient, power transmission coefficient and the read range as a function of frequency are illustrated. The performance of the tag antenna in the presence of the dielectric box and different object materials inside the box is illustrated. The effect of the objects that are placed in the center of the dielectric box didn't have a significant effect on the performance of the tag antenna; there is a small shift in the resonance frequency but still within the operating frequency band. Both the power transmission coefficient and the read range change with the object material. The backscattering properties of the tag antenna have been studied. The differential radar cross-section of the tag antenna is calculated for different antenna loads.

In this paper, a novel source localization scheme is proposed based on the unitary ESPRIT algorithm with back ray tracing technique and the city electronic maps. Our scheme can be summarized into two steps. First, the unitary ESPRIT algorithm is employed to estimate the angles and delays of the arrival rays radiated from the source. Second, based on the obtained information we devise a back ray tracing technique to recover the signal propagation paths according to the Geometrical Theory of Reflections and the city electronic map. After these two steps the source position can be obtained by averaging all the estimated positions. In order to minimize estimated errors caused by the Unitary ESPRIT, a valid-range selection criterion for the judgment of the validity of the estimated position data is proposed. On the other hand, we introduce a path length weighting factor to reduce the estimated errors caused by the terrain data inaccuracy. This position method can locate both the line of sight (LOS) and non-line of sight (NLOS) sources efficiently and it also can locate multi-sources simultaneously. Six simulations are carried out in three terrain scenarios. The numerical results demonstrate that our model can be applied to estimate the positions for both 2D and 3D cases. The accuracy of our model for a cell of 80 m × 45 m can reach 10 m when SNR is greater than 10 dB.

A reconstruction algorithm for two- and three- dimen-sional microwave imaging is proposed. The present effort is focused on the reconstruction of conductivity (σ) and permittivity (ε_r) distri-butions aiming at a technique serving medical imaging, while perme-ability imaging can be easily incorporated to serve geophysical geophysical prospecting as well. This work constitutes the most recent one within the effort of extending our Modified Perturbation Method (MPM) from static to high and now microwave frequencies. MPM is an approximate method based on an exact Sensitivity or Jacobian matrix for an iterative update of an initial (σ, ε_r) guess until convergence. This method is proved almost immune of the problem inherent ill-posedness, but its robustness is actually gained by paying a penalty of compromised accuracy in the final achieved image. However, this image can be fine tuned by formulating and solving an exact inverse problem. Regarding the involved Jacobian matrix, this is evaluated through closed form expressions obtained through an Adjoint Network Theorem in conjuction with the electromagnetics reciprocity theorem. The field distributions required for its evaluation are readily available from the always required forward problem solutions on the assumed (σ, ε_r) distributions. Herein, the finite element method along with absorbing boundary conditions are employed for the forward problem electromagnetic simulation.

An efficient approach is utilized for extracting the modal parameters of high frequency structures and their sensitivities with respect to all the design parameters. Using one FDTD simulation, the modal parameters of all the guided and leaky modes are extracted over the frequency band of interest. An adapted version of the matrix pencil method is utilized for efficient extraction of the modal parameters. In addition, using no extra simulations, the sensitivities of the propagation constants with respect to all the design parameters of the structure are extracted regardless of their number. The computational time is a small fraction of the cost of similar approaches.

Electromagnetic fields in a cavity filled with double negative dispersive medium and bounded by a closed perfectly conducting surface is studied in the Time Domain. The sought electromagnetic fields are found in a closed form by using decomposition over cavity modes and solving in TD the differential equations for the time varying mode amplitudes. Some features of frequency response of such an electromagnetic system are presented. Waveforms of electromagnetic fields excited by a wideband pulse are considered.

There are three approaches for the solution of the diffraction problem of plane waves by an impedance half-plane in the literature. The diffracted field expressions, obtained by the related methods, are compared numerically. The examination of the scattered field shows that the most reliable solution is the field representation of Raman and Krishnan. Since the diffracted fields of Senior and Maliuzhinets do not compensate the discontinuities of the geometrical optics waves at the transition regions.

We combine the analytic eigen mode expansion method with the finite-difference, frequency-domain (FD-FD) method to study two-dimensional (2-D) optical waveguide devices for both TE and TM polarizations. For this we develop a layer-mode based transparent boundary condition (LM-TBC) to assist launching of an arbitrary incident wave field and to direct the reflected and the transmitted scattered wave fields back and forward to the analytical regions. LM-TBC is capable of transmitting all modes including guiding modes, cladding modes and even evanescent waves leaving the FD domain. Both TE and TM results are compared and verified with exact free space Green's function and a semi-analytical solution.

After a report on strange electromagnetic resonances emerging in an isotropic paraelectric Menger sponge (MS) now known as a photonic fractal, vigorous studies began to reveal their properties. However, the mechanics of how the resonances occur is still unknown. This report focuses on the findings that the resonances can be perturbation-theoretically identified as those originally occurring in an isolated dielectric cube, and that they arise within band gaps and uncouple with Bloch modes for a certain multiperiodic lattice. This interpretation is justified by the fact that the MS can be considered as a cube embedded in the lattice rather than the outcome of conventional recursive fractal structuring operations. An experimental formula for resonance conditions already reported can be derived from this interpretation.

A system generating 1.8 GHz electromagnetic fields for bio-medical and behavioral study on laboratory animals was designed and implemented. The system is based on a reverberation chamber. An input power up to 5 W can be sent to an indoor transmitting antenna and an electric field strength (E) more than 90 V/m can be reached inside the chamber. The system was characterized at different input powers measuring E in different points by means of a miniature sensor. Then, boxes with 300 cc of physiological liquid inside were realized as simple phantoms simulating laboratory animals (rats) and E inside the liquid was measured, performing several simulations by moving the phantoms (1,2) in the chamber and/or putting them still in different positions. On the basis of these measurements, the SAR (Specific Absorption Rate) and the Pe (power efficiency = SAR/input power) were determined at different powers. The actual system is characterized by a low power efficiency with respect to the "in vivo" exposition systems based on transversal electromagnetic (TEM) cells. Its advantage is to have inside the chamber a habitat similar to the usual one for the laboratory animals.

A single-stage ultra-wideband (UWB) CMOS low noise amplifier (LNA) employing interstage matching inductor on conventional cascode inductive source degeneration structure is presented in this paper. The proposed LNA is implemented in 0.18 μm CMOS technology for a 3 to 5 GHz ultra-wideband system. By careful optimization, an interstage inductor can increase the overall broadband gain while maintaining a low level of noise figure of an amplifier. The fabricated prototype has a measured power gain of +12.7 dB, input return loss of 18 dB, output return loss of 3 dB, reverse isolation of 35 dB, noise figure of 4.5 dB and input IP3 of -1 dBm at 4 GHz, while consuming 17 mW of DC dissipation at a 1.8 V supply voltage.

A reconfigurable patch antenna consisting of a square patch with two cross-shaped diagonal slots is presented. The proposed design approach is based on the use of two pairs of switches in order to obtain both frequency and polarization reconfigurability. Specifically, three different polarization states have been obtained: A Right-Hand Circular Polarization, a Left-Hand Circular Polarization and a Linear Polarization. Experimental results, referred to a realization on a FR4 substrate of the layouts corresponding to the useful switch configurations, are reported.

In this paper, a compact, wide fractional bandwidth bandpass filter using a new open slot split ring resonator (OSSRR) defected ground structure and compact microstrip resonating cell (CMRC) is presented. OSSRR is the modified and dual version of the open split ring resonator (OSRR). The band pass filter (BPF) is constructed by cascading lowpass and highpass sections designed using CMRCs and OSSRR respectively. The designed BPF has wide fractional bandwidth of 74%, sharp passband to stopband transition and low passband insertion loss of less than 1 dB. The simulated results are well validated by the experimental results.