The quality of a magnetic resonance image can be reliably measured by the signal-to-noise ratio. This widely accepted parameter is a function of the magnetic field generated by the coil and the electric field produced by the sample to be imaged. A simple numerical method is proposed to calculate the coil signal-to-noise ratio of a circular-shaped coil and a spherical phantom. The phantom is composed of two-concentric sphere simulating a brain-skull model. The electromagnetic fields produced were then numerically computed by solving Maxwell's equations with the finite element method implemented in a commercial software tool. The electric and magnetic fields were used to numerically determine the signal-to-noise ratio using the quasi-static approach. The numerical results demonstrated that this simple method is able to calcualte the signal-to-noise ratio of surface coils with simple coil geometries involving a simulated phantom.

Two planar monopole antennas with wide impedance bandwidth are designed. A full-wave method of moment (MoM) based on the electric field integral equation (EFIE) is applied to analyze the impedance bandwidth and radiation performance of the monopoles. Meanwhile, the multilevel fast multipole algorithm (MLFMA) is employed to reduce the memory requirements and computational time. Experimental results such as the impedance bandwidth and radiation patterns are also presented. The good agreement between the experimental and numerical results well demonstrates the efficiency and accuracy of the MLFMA code. Both the experimental and numerical results show that the two planar monopole antennas possess good input impedance and radiation performance over the AMPS, GSM900, and DCS band. As the proposed antennas can achieve such wide impedance bandwidth with relatively low profile, they are very suitable for multi-band mobile communication systems.

An exact form for the equivalent edge current is derived by using the axioms of the modified theory of physical optics and the canonical problem of half-plane. The edge current is expressed in terms of the parameters of incident and scattered rays. The analogy of the method with the boundary diffraction wave theory is put forward. The edge and corner diffracted waves are derived for the problem of a black half-strip.

An iterative reconstruction algorithm for three-dimensional (3-D) microwave tomography by using time-domain microwave data is applied to detect breast tumor. A numeric breast model with randomly distributed glandular tissues (random size and permittivity) with a tumor is designed for the calculation of synthetic microwave data. An "air phantom" consisting of a section of polyvinyl chloride (PVC) pipe filled with styrofoam and a thin glass cylinder is constructed for collecting microwave data in laboratory. The "breast" and "air phantom" are reconstructed. Reconstruction results show that the "tumor" in the breast is clearly reconstructed, and the glass cylinder is successfully reconstructed too.

High frequency field expressions are derived at the focal points of a paraboloidal reflector placed in a homogenous and reciprocal chiral medium. Firstly Geometrical Optics (GO) field expressions are derived for the paraboloidal reflector placed in chiral medium. As the GO fails at the focal points, so Maslov's method has been used to find the field expressions which are also valid around the focal point. By using hybrid space, Maslov's method combine the simplicity of ray theory and the generality of Fourier Transform method. Some numerical results including contour plots and line plots around the focal region of paraboloidal reflector placed in chiral medium are obtained using the derived expressions.

This paper presents a generalized approach to design an electromagnetically coupled microstrip ring antenna for dual-band operation. By widening two opposite sides of a square ring antenna, its fractional bandwidth at the primary resonance mode can be increased significantly so that it may be used for practical applications. By attaching a stub to the inner edge of the side opposite to the feed arm, some of the losses in electrical length caused by widening can be regained. More importantly, this addition also alters the current distribution on the antenna and directs radiations at the second resonant frequency towards boresight. It has also been observed that for the dual frequency configurations studied, the ratio of the resonant frequencies (f_r2/f_rr) can range between 1.55 and 2.01. This shows flexibility in designing dual frequency antennas with a desired pair of resonant frequencies.

An innovative preconditioner has been developed in this work. It significantly improves the convergence of the iterative solvers applied to electromagnetic radiation problems by a renormalization of the matrix equation. The preconditioner balances the disparities in terms of magnitude and units caused by the strong self-coupling of the antennas, the non-uniformity of the meshes and also by the coexistence of wire and surface basis functions. It can be easily integrated into different electromagnetic solvers with a negligible impact on the computational cost on account of its simple implementation.

In this paper, a complementary meander line split-ring resonator (C-MLSRR) model is proposed and its equivalent circuit model is given. Prototypes of microstrip lines loaded with C-MLSRR with and without series capacitive gaps are designed, which exhibit a negative permittivity behavior (without series capacitive gaps) and a left-handed behavior (with series capacitive gaps), respectively, at two different frequencies. The application of the C-MLSRRs in compact dual band (i.e., 2.52 GHz and 5.35 GHz) notch filter for wideband application is presented to highlight the unique features of the C-MLSRRs.

A repeaterless hybrid CATV/16-quadrature amplitude modulation (QAM) orthogonal frequency-division multiplexing (OFDM) transport system employing half-split-band and remote light injection techniques is proposed and demonstrated. Over an 80-km SMF transmission without optical amplification, good performances of carrier-to-noise ratio (CNR), composite second order (CSO), and composite triple beat (CTB) were obtained for CATV band; simultaneous high CNR and low bit error rate (BER) values were achieved for 16-QAM OFDM band. This architecture presents a feasible way to transmit both analog and digital video signals.

The improved high-frequency method for solving the bistatic scattering from electrically large conductive targets is presented in this paper. Since the previous physical optical methods overlooked the current impact of shadow zone and led to the increasing problems of the large angle bistatic calculation, the improved method is deduced by introducing the current marching technique into the conventional physical optical method. Combined with the graphical-electromagnetic computing method that extracted the illuminated and shadow facet in accordance with the direction of the incident sort iteration, one may calculate the bistatic radar cross-section of a conductive targets object. The numerical results show that this method is efficient and accurate.

Phase modulation is critical due to its applicability in varied RF devices such as phased array antennas, radars to name a few. In this paper, we report experimental data on phase modulation in the X-band frequency using tunable metamaterials such as a planar design of stacked dual split ring resonators (DSRRs) of 3mm thickness at 8.5 GHz. Modulation was brought about by switching between the open and closed states of the rings causing a net change in the effective refractive index and thereby producing a phase variation. One and two dimensional free-space scanning experiments were carried out where a phase modulation of 62 degrees was demonstrated. The measured data matched well with the numerically simulated results.

The non reciprocal effect of such devices as microstrip and coplanar isolators can be based on the field displacement phenomenon induced by a magnetized ferrite material. The structure under study is made from a ferrite thin-film deposited on a alumina substrate. A non symmetrical coplanar line is put on the ferrite film and the absorber is made from either a graphite film or a Tantalum Nitride film or a copper slab. In order to work in millimeter wave range the barium ferrite was selected. Moreover, the size of the component could be less than the circulator one. The small size and simple shape are the principal advantages of a coplanar isolator structure.

A 6:1 unequal Wilkinson power divider that combines the advantages of a coplanar waveguide with an electromagnetic bandgap (EBG CPW) and microstrip line structures suitable for a PCB circuit design is proposed. The highly characteristic impedance transmission line (TL) is realized by employing the proposed EBG CPW structure, which is difficultly achieved using the conventional microstrip line or CPW due to printed circuit board (PCB) process limitations. The proposed EBG structure enables the CPW line to have a very high characteristic impedance of over 207 Ω. The fabricated 6:1 power divider delivers excellent matching and isolation performances with more than 34 dB at 1.5 GHz. It also has exact dividing ratios of 8.46 dB and 0.7 dB at two output ports, respectively.

Brillouin fiber laser (BFL) is demonstrated using a piece of photonic crystal fiber (PCF) in conjunction with a Bismuth-based erbium-doped fiber (Bi-EDF) as the gain media with a simple ring resonator. The proposed BFL operates at wavelength of 1574.08 nm, which is 0.08 nm shifted from the Brillouin pump wavelength with a maximum peak power of 8 dBm. The BFL has a side mode suppression ratio and 3 dB bandwidth of approximately 23 dB and 0.02 nm respectively limited by the optical spectrum analyzer resolution. The BFL is also stable at room temperature and compact due to the use of only 20 m long of PCF and 215 cm long of Bi-EDF.

In a dual-plane compact electromagnetic band-gap (CEBG) microstrip structure, patches are etched periodically in the ground plane to prohibit the propagation of electromagnetic waves in certain frequency bands so as to provide filtering functionality. However, the existence of the etched patches in the ground plane becomes a natural concern for the reason that these structures might be more prone to electromagnetic interference from nearby radiating components as compare to a microstrip filter with a perfect ground plane. In this paper, an investigation into the electromagnetic susceptibility of a C-EBG filter structure is presented. This study examines the effects of the the interference source on the performance of a C-EBG structure in terms of the relative frequency, power level, position, and polarization. From the study, useful guidelines are drawn for the applications of EBG microstrip structures in an environment rich in electromagnetic interference.

This paper presents an efficient and simple approach of implementing the Landau-Lifshitz-Gilbert (LLG) equation of magnetisation motion within the Finite-Difference Time-Domain (FDTD) method. This combined electromagneticmicromagnetic simulation technique is particularly important for modeling electromagnetic interaction with lossy magnetic material in the presence of current and magnetic sources, particularly at very high frequencies. The efficient implementation involves simple two-point spatial interpolations that are applicable to two and three-dimensional FDTD grids, and uses a stable iterative algorithm for the time integration of the LLG equation. A ferromagnetic resonance numerical experiment on a rectangular Permalloy prism excited through its cross-section by a non-uniform pulse field from a transmission line was carried out for the purpose of verifying the combined FDTD-LLG computations. The numerical results were in good agreement with linearised analytical solutions of the LLG equation for uniform and non-uniform precession modes. This paper also presents a brief investigation on the use of non-staggered FDTD grid schemes to model magnetic material using the LLG equation, and indicates that the classical FDTD staggered scheme offers simplicity in implementation and more accuracy for modeling wave interaction with lossy magnetic material than the non-staggered schemes based on Maxwell's equations formulation.

The unified theory of near-field-far-field transformation techniques with spiral scannings for quasi-spherical antennas is extended in this paper to the case of nonspherical ones, i.e., antennas with two dimensions very different from the third one. To this end, such a kind of antennas is no longer considered as enclosed in a sphere, but in a proper convex domain bounded by a rotational surface. The extension, heuristically derived by paralleling the rigorous procedure valid when adopting the spherical source modelling, allows the overcoming of its main and serious drawbacks. In fact, the corresponding near-field-far-field transformations with spiral scannings for nonspherical antennas make use of a reduced number of near-field measurements and, above all, allow one to consider measurement surfaces at a distance smaller than one half the antenna maximum size, thus remarkably reducing the error related to the truncation of the scanning zone. These are very important features, which make the spiral scannings more and more appealing from the practical viewpoint. Some examples of the application of this theory to spirals wrapping the conventional scanning surfaces employed in the near-field-far-field transformations are reported for various source modellings, and the accuracy and robustness of the far-field reconstructions are assessed.

A perfect electric conductor placed in chiral nihility medium and excited by a uniform plane wave has been considered as an original problem. Using fractional operators, solutions to Maxwell equations which may be regarded as intermediate step between the original solution and dual to the original solution are determined. Each fractional operator is composed of fractional curl operator. As more than one dual to original solution exists, so in each case, corresponding impedance of the fractional dual reflector has been determined.

The conventional perfectly matched layer (PML) absorbing boundary condition is shown to be unstable when it is extended to truncate the boundary of the double negative (DNG) medium. It is a consequence of the reverse directions of the Poynting and phase-velocity vectors of plane waves propagating in such material. In this paper, a modified uniaxial PML (UPML), which is stable for the DNG medium, is derived. The auxiliary differential equation technique is introduced to derive the discrete field-update equations of DNG-UPML. Numerical results demonstrate the effectiveness and stability of the new UPML for the DNG medium.

A new subspace method based on spatial-temporal structure is presented for estimation of directions-of-arrival (DOA's) and ranges of multiple near-field sources impinging on an array of sensors. The arrival angle and range parameters are directly given by the eigenvalues of a set of constructed matrices and the computational complexity of the proposed method is lower than those of several available methods which do not require search operation. Simulation results show that the proposed method outperforms an ESPRIT-like method.