A 1800 MHz transverse electromagnetic wave (TEM) cell is introduced for experiments investigating effects on biological samples caused by the exposure from mobile communications. To characterize and quantify the exposure environment in the setup for standardized in vitro experiments, we evaluate the dosimetry and the exposure-induced temperature rise in cultured cells. The study is numerically based on the finite-difference time-domain (FDTD) formulation of the Maxwell equations and the finite-difference formulation of the bioheat transfer equation, with all algorithms and models strictly validated for accuracy. Two sample formations of cells are considered including the cell layer and the cell suspension cultured in the 35 mm Petri dish. The TEM cell is designed to establish standing waves with the maximum E field and the maximum H field, respectively, at the position of the Petri dish. The Petri dish is oriented to E, -E, H, k, and -k directions of the incident field, respectively, to receive the exposure. The specific absorption rate (SAR) is calculated in cells for 10 exposure arrangements combined from the maximum fields and Petri dish orientations. A comparison determines the best arrangement with the highest exposure efficiency and the lowest exposure heterogeneity. The dosimetry and the exposure-induced temperature rise in cells are evaluated for the selected arrangement. To avoid thermal reactions caused by overheating, the maximum temperature rises in cells are recorded during the exposure. Based on the records, the temperature control is performed by setting limits to the exposure duration. We introduce a method to further reduce the exposure heterogeneity and evaluate the influence of the Petri dish holder on the dosimetry and temperature rise. The study compares the TEM cell to the waveguide, as well as the standing wave exposure to the propagating wave exposure. The TEM cell and the selected arrangement of the standing wave exposure improve the exposure quality over the traditional methods, with increased efficiency and decreased heterogeneity of the exposure.

In this article, we introduce an improved optimization based technique for the synthesis of circular antenna array. The main objective is to achieve minimum side lobe levels, maximum directivity and null control for the non-uniform, planar circular antenna array. The design procedure utilizes an improved variant of a prominent and efficient metaheuristic algorithm of current interest, namely the Differential Evolution (DE). An efficient classical local search technique called Solis Wet's algorithm is incorporated with the competitive Differential Evolution. While the competitive DE is used for the global exploration, Solis Wet's algorithm is employed for local search. Combining the capability of both techniques the hybrid algorithm exhibits improved performance for circular array design problem. Three examples of circular array design problems are considered to illustrate the effectiveness of the hybrid algorithm cDESW (Competiteve Differential Evolution with Solis Wet's technique). The design results obtained using cDESW has comfortably outperformed the results obtained by other state-of-the-art metaheuristics like CLPSO, JADE.

In this paper, a new theoretical approach for the classification of multiple reflections in time-domain e.m.~inverse scattering of multi-layered media is presented. The existence of multiples limits the capabilities of inversion algorithms, thus suitable identification and suppression techniques should be applied to reduce this undesired effect. Assuming a scenario composed of loss-less and non-dispersive media, and providing an accurate time delay estimation (TDE) of backscattered signals, the proposed method allows not only to evaluate the presence of multiples and discriminate them from primary reflections, but also to determine their propagation paths. Preliminary tests performed on FDTD simulated data have shown its potentialities to effectively handle multiple reflections and therefore to enhance the e.m. signals backscattered by primary reflectors.

This paper presents a new general formula for calculating the magnetic force between inclined circular loops placed in any desired position. This formula has been derived from the Lorentz force equation. All mathematical procedures are completely described to define the coil positions that lead to a relatively easy method for calculating the magnetic force between inclined circular loops in any desired position. The presented method is easy to understand, numerically suitable and easily applicable for engineers and physicists. The obtained formula is given in its simplest form from the already existing formulas for calculating the magnetic force between inclined circular loops. We validated the new formula through a series of examples, which are presented here.

In this paper, a compact, planar ultrawideband (UWB) monopole microstrip antenna is proposed which offers dual band notch characteristics with enhanced rejection at frequency bands centered at 3.4 GHz and 5.5 GHz. To realize enhanced band notched characteristics at 3.4 GHz, a pair of filters is incorporated which includes an inverted `L' shaped slot and a twisted `J' shaped slot in the patch element. Another pair of filters comprises of a spur line filter in the feed line and `U' shaped slot in the patch are used to get a strong frequency band rejection centered at 5.5 GHz. Step by step development of the antenna with its analysis in frequency and time domain is presented. The prototype is fabricated and the measured results are presented which are in close similarity to the simulated results.

Nowadays, applications of Frequency Selective Surfaces (FSS) for radar absorbing materials (RAM) are increasing, but it is still a challenge to select a proper FSS for a particular material as well as the dimensions of FSS for optimized absorption. Therefore, in this paper an attempt has been made to optimize the dimensions of FSS for microwave absorbing application using Genetic Algorithm (GA) approach. The considered frequency selective surfaces are composed of conducting patch elements pasted on the ferrite layer. FSS are used for filtration and microwave absorption. In this work, selection and optimization of FSS with radar absorbing material has been done for obtaining the maximum absorption at 8-12 GHz frequency. An equivalent circuit method has been used for the analysis of different FSS, which is further used to design fitness function of GA for optimizing the dimensions of FSS. Eight different available ferrite materials with frequency dependant permittivities and permeabilities have been used as material database. The GA optimization is proposed to select the proper material out of eight available materials with proper dimensions of FSS. The optimized results suggest the material from database and dimensions of FSS. The selected material is then mixed with epoxy and hardener, and coated over the aluminium sheet. Thereafter, all five FSS were fabricated on ferrite coated Al sheets using photolithographic method followed by wet etching. The absorption was measured for all FSS using absorption testing device (ATD) method at X-band. Absorption results showed that significant amount of absorption enhanced with the addition of proper FSS on radar absorbing coating.

A printed ultra-wideband (UWB) monopole antenna with both tunable and switchable band-notched characteristics is proposed. An embedded resonant slot loaded with a varactor and a pin diode controlled by DC signal through one common bias network is employed to tune and switch the notch band. In the ``all-pass'' state when the two diodes are partially turned on, the power consumption of this active antenna is only 2.4 μW. Measured return loss, radiation pattern, gain and group delay of the introduced antenna are presented in this paper.

Microstrip bandpass filters using a triple-mode patch-loaded cross resonator are presented in this work. First, a square patch is added at the center of a cross resonator to separate the resonant frequencies of the 1st and 2nd modes. Then, a pair of narrow slots is etched into the square patch along its symmetrical plane to split the 1st resonant mode and its degenerate mode. By changing the patch size and the slot length, the above three modes are appropriately adjusted. Two prototype filters with open-ended and stub-loaded coupled-lines are designed and fabricated to verify the design principle and to further suppress the lowest harmonic passband, respectively. Predicted results agree well with the measured ones.

The characteristics of a two-dimensional (2D) left-handed traveling-wave field-effect transistor, which is two 2D composite rightand left-handed (CRLH) transmission lines with both passive and active couplings, are discussed for generating non-attenuated waves having left-handedness in 2D. In this study, the design criteria for wave amplification are described, and the results from numerical calculations obtained by solving the transmission equations for the device are presented.

A modified Cauchy method which generates accurate duplexer and triplexer rational models from either measurements or electromagnetic analysis is presented in this paper. The modified Cauchy method has some advantages over the conventional Cauchy method because it takes into account the relationship between the transmission coefficients of each channel filter and reflection coefficient. It is suitable for duplexer and triplexer whose channel filters are connected through resonating junction. The total least square method is used to solve the system matrix. Synthesized numerical duplexer and triplexer examples verify the method successfully.

This paper presents the design and development of corner truncated rectangular microstrip antenna comprising U and inverted U-slot for multiband tunable operation, wide impedance bandwidth, and high gain. By incorporating U and inverted U-slots of optimum geometry on the radiating patch the proposed antenna operates between 3 to 12 GHz at different frequency bands and giving a peak gain of 1.73 dB without changing the nature of broadside radiation characteristics, compared to conventional rectangular microstrip antenna. The experimental and simulated results are in good agreement with each other. Design concepts of the antenna are given. The experimental results are presented and discussed. The proposed antennas may find applications in WiMax, HIPERLAN/2, and radar communication systems.

The focusing properties of six array configurations in the form of square, square with interlaced elements, square ring, cross (+) shape, cross (X) shape, and square ring plus diagonals shape arrays are investigated. The performance parameters, such as field distribution in the focal region, size of the focal spot, depth of field, level of field at focal point, and sidelobe structure, are compared. Computer simulations using MTALAB environment are performed in the investigations. The square ring and square ring plus diagonals configurations show favorable focusing properties. The resultant field patterns will help to find the arrays usefulness for hyperthermia and imaging applications.

Characteristics of reflected power from a planar interface of chiral and/or chiral nihility media have been investigated theoretically. Focus of the study is tunneling and rejection of power associated with these interfaces. Effect of polarization of incidence field and parametric dependence on reflected power have been noted. It is found from numerical results that power tunneling and rejection have strong dependency on the polarization of incidence field, angle of incidence, and chirality parameter.

Long data collecting time is one of the bottlenecks of the stepped-frequency continuous-wave ground penetrating radar (SFCW-GPR). We discuss the applicability of the Compressive Sensing (CS) method to three dimensional buried point-like targets imaging for SFCW-GPR. It is shown that the image of the sparse targets can be reconstructed by solving a constrained convex optimization problem based on l₁norm} minimization with only a small number of data from randomly selected frequencies and antenna scan positions, which will reduce the data collecting time. Target localization ability, performance in noise, the effect of frequency bandwidth, and the effect of the wave travel velocity in the soil are demonstrated by simulated data. Numerical results show that the presented CS method can reconstruct the point-like targets in the right position even with 10% additive Gaussian white noise and some wave travel velocity estimation error. p

We propose an improved method of iterative physical optics (IPO) to analyze electromagnetic scattering by open-ended cavities. The traditional IPO method uses a fixed number of iterations; if this number is too small, the accuracy of the estimated monostatic radar cross section (RCS) of open-ended cavities degrades as the incident angle of the incident field increases. The recently-introduced adaptive iterative physical optics-change rate (AIPO-CR) method uses a variable number of iterations; compared to the IPO method, it predicts monostatic RCS more accurately, but requires more computation time. In this paper, a new algorithm is devised to improve both the monostatic RCS prediction accuracy of the IPO method, and the computational efficiency of the AIPO-CR method. The proposed method, iterative physical optics-retained previous solution (IPO-RPS), calculates the currents at one incident angle, then reuses them as the initial currents of iterations for the next incident angle. In simulations of the monostatic RCS for various open-ended cavities, the IPO-RPS method was more accurate than the traditional IPO method, and computationally more efficient than both the IPO and AIPO-CR methods.

Electromagnetic Vulnerability (EMV) testing of ground vehicles and helicopters is (by necessity) performed in the immediate presence of ground surfaces (natural earth, asphalt, concrete, ship decks, and other finitely conducting grounds). The impact of the nature of these grounds on the EM coupling to the various vehicles being tested is the focus of this work. As one approach to addressing these issues quantitatively, personnel at Redstone Test Center Electromagnetic Environmental Effects (RTC/E3) Division have combined measurements on a semi-canonical physical structure along with EM modeling. In particular, a hollow 25 foot long, 4 foot diameter aluminum cylinder with a finite slot (~8 in wide) running along its entire length is positioned over (and near to) a finite conducting ground plane. Measurements of the electric fields produced both in the slot aperture and inside the hollow cylinder by an external log period dipole antenna (LPDA) positioned (broadside to the horizontal cylinder) approximately 5\,m away radiating both vertical and horizontal polarizations, respectively, are presented and discussed. The entire experimental setup (aluminum cylinder, finite aluminum ground plane, and radiating LPDA) are enclosed inside an RF anechoic chamber (inside dimensions between the respective tips of the anechoic pyramids of approximately 19 m х 9.0 m х 5.0 m). A moment method model (CARLOS) is also developed and the fields in the aperture and inside the cylinder are compared to the measured fields.

This paper presents a method for synthesizing coupled resonator diplexers composed of TX and RX filters (two types of junctions connecting the TX and RX filters are considered). For the first junction type, the common port is directly coupled to the first resonator of the TX and RX filters, respectively. For the second junction type, common node is realized by adding an extra resonator besides those of the TX and RX filters. The method is based on the evaluation of the characteristic polynomials of the diplexer using the proposed linear frequency transformation and well-established method, and then the "N + 3" coupling matrix of overall diplexer can be obtained using hybrid optimization methods. Two diplexers have been designed and fabricated to validate the proposed method.

In order to overcome the problems facing Cr-Cu-Au metallization, such as discoloration, diffusion of Cu into Au, a four-layer metallization Cr-Cu-NiP-Au is demonstrated on alumina substrate for microwave integrated circuit (MICs). A amorphous and nonmagnetic NiP barrier layer is used to avoid the diffusion of Cu into Au through the grain boundaries, which are the low activation energy path for diffusion at moderate temperature. In this view, properties of Cr-Cu-NiP-Au metallization, such as sheet resistance, solderability, bondability and adhesion strength, are evaluated. Further integrity of Cr-Cu-NiP-Au structure is evaluated by subjecting to this structure to multiple temperature cycles test. Visual observation is carried our before and after the thermal cycling test. No degradation is observed as the consequence of thermal cycling test. Test and evaluation are carried out for a multi-section broadband power divider (1 : 2) on this metallization (metal thickness 12-12.5 microns) in the 0-6 GHz frequency range. Insertion loss, return loss and isolation are comparable with Cr-Cu-Au (metal thickness 5.0-6.0 microns). Performance of the power divider and properties of this metallization system reveal its novelty over the existing.

An equivalent circuit model of coaxial probes is derived directly from the intrinsic via circuit model. As all the higher-order evanescent modes have been included analytically in the parasitic circuit elements, only the propagating mode needs to be considered by the simplest uniform-current model of a coaxial probe in numerical solvers such as finite element method (FEM) or finite difference time domain (FDTD). This avoid dense meshes or sub-gridding techniques and greatly reduces the computational efforts for accurate calculation of the probe input impedance. The derived equivalent circuit model and the new feeding technique have been validated by both analytical formulas and numerical simulations.

The direct position determination (DPD) method can improve the location accuracy compared with the traditional two-step location methods due to omitting the intermediate procedure of estimating the measurement parameters. However, the DPD methods presented so far are significantly more complex than the two-step approach. To overcome the shortcomings of the published DPD algorithms, a novel multi-target direct localization approach is firstly proposed by exploiting the jointly sparse property in the discrete spatial domain. The main idea of this paper is that the location estimation can be obtained by finding the sparsest solution according to the predefined overcomplete basis. Furthermore, the locations of targets can be obtained from noisy signals, even if the number of targets is not known a priori. Experimental results demonstrate that the proposed algorithm has superior positioning accuracy to other DPD methods and improves computational efficiency greatly.