We propose a hybrid finite-difference frequency-domain method to study the perpendicular crossing waveguide, dielectric and microwave, TE and TM modes, by exploiting built-in structural symmetries in these waveguide devices. In the plus (+) symmetry model, the complete solution is obtained by solving two rectangular-shaped quarter structures each with two transparent boundaries and two symmetry boundaries. For the cross (x) symmetry model, solutions of four triangular-shaped quarter structures are needed but each with only one transparent boundary. Numerical results are verified by comparison between these two models and with the power conservation test. We show the total and the fundamental-mode, coupling coefficients of the reflected, cross and through power in the crossing waveguide as functions of the normalized frequency.

A novel DOA finding method for conformal array applications is proposed. By using sub-array divided and interpolation technique, ESPRIT-based algorithms can be used on conformal arrays for 1-D and 2-D DOA estimation. In this paper, the circular array mounted on a metallic cylindrical platform is divided to several sub-arrays, and each sub-array is transformed to virtual uniform linear array or virtual uniform planar array through interpolation technique. 1-D and 2-D direction of arrivals can be estimated accurately and quickly by using LS-ESPRIT and 2-D DFT-ESPRIT algorithms, respectively. This method can be applied not only to cylindrical conformal array but also to any other arbitrary curved conformal arrays. Validity of this method is proved by simulation results.

Electromagnetic shields are designed to optimize the performance for shielding effectiveness and reflectivity. Multilayered laminates of different materials are developed to achieve excellent results in terms of not only in shielding effectiveness but also for reflectivity. In this paper, a three layered laminate is considered for estimation of the required parameters in the X-band frequency range. A sandwich of conductive polymer between a conductor and microwave absorber yields very good performance. Several investigations were carried out for the estimation of shielding effectiveness and reflectivity of the three layered laminate structure at different thickness of each layer and for a combination of different materials.

A double-side radiating leaky-wave antenna based on composite right/left-handed (CRLH) coplanar-waveguide (CPW) is proposed. Dispersion diagram of the unit cell is investigated, and balanced property is confirmed. Thus, the CRLH leaky-wave antenna can have backfire radiation due to the left-handed property of the CRLH structure and broadside radiation at the balancing frequency point. The measured results show that the proposed antenna can offer a scanning angle covering almost backfire-to-endfire directions.

A combined method of the non-uniform fast fourier transform (NUFFT) migration and the least-square based matching pursuit decomposition (MPD) algorithms is proposed to obtain better discrimination and interpretation for subsurface from ground penetrating radar (GPR) signals. By using the modified NUFFT migration algorithm, a fast and high resolution GPR reconstruction can be obtained with an additional reduction in storage and computation requirements. By incorporating the MPD algorithm into a migration method, denoised reconstructions are obtained to enhance objects detection, including the identification of objects' geometries and the estimation of their sizes and locations. Several examples from synthetic data and field data are demonstrated to establish the effectiveness of the synergic effect by comparing it with the conventional migration methods.

A theoretical analysis of the properties of the defect modes in a one-dimensional defective photonic crystal (PC) is given. Two defective PCs stacked in symmetric and asymmetric geometries are considered. The defect modes are investigated by the calculated wavelength-dependent transmittance for both TE and TM waves. It is found that there exists a single defect mode within the photonic band gap (PBG) in the asymmetric PC. There are, however, two defect modes within the PBG in the symmetric one. The dependences of defect modes on the angle of incidence are illustrated. Additionally, the effect of defect thickness on the number of defect modes is also examined.

The modeling of quasi-static optimization problems often involves divergence-free surface current densities. In this paper, a novel technique to implement these currents by using the boundary element method framework is presented. A locally-based characterization of the current density is employed, to render a fully geometry-independent formulation, so that it can be applied to arbitrary shapes. To illustrate the versatility of this approach, we employ it for the design of gradient coils for MRI, providing a solid mathematical framework for this type of problem.

Understanding the propagation of light in continuous inhomogeneous materials is important to design optical structures and devices. To have accurately numerical calculations Berreman's 4×4 propagation matrix method is generally used, and layer approximation, i.e., the whole one-dimensional continuous inhomogeneous material is divided into many small homogeneous layers, is assumed. However, this layer approximation is only correct up to the second-order of the layer thickness. To efficiently solve Berreman's first-order differential equation, a simple fourth-order symplectic integrator is presented. The efficiency of the fourth-order symplectic integrator was studied for a cholesteric liquid crystal. Numerical results of reflectance spectra show that the fourth-order symplectic integrator is highly efficient in contrast to the extensively used fast 4×4 propagation matrix.

In this paper, a compact and simple microstrip-fed slot antenna is proposed for ultra-wideband (UWB) applications, which consists of a circular patch and an open T-slot to realize the microstrip-line to slot transition well over a widened frequency range. The simulations and measurements show that this simple structure with the novel design generates a broadband impedance bandwidth of 10dB return loss from 2.5 to 12.5 GHz (BW=133.3%) adjustable by variation of its parameters. Details of the antenna design and experimental results of the constructed prototype are presented. In addition, a geometric parameters study of the proposed antenna is able to provide more useful information for antenna design.

A uniform asymptotic solution is presented for evaluating the field diffracted by the edge of a lossy double-negative metamaterial layer illuminated by a plane wave at skew incidence. It is given in terms of the Geometrical Optics response of the structure and the transition function of the Uniform Geometrical Theory of Diffraction, and results easy to handle. Its accuracy is well-assessed by numerical tests and comparisons with a commercial solver based on the Finite Element Method.

In this work, the introduction of Defected Microstrip Structures and Defected Ground Structures is presented to improve the performance of a traditional stepped-impedance microstrip lowpass filter. The attenuation in the stop-band is enhanced by more than 15 dB and selectivity is increased, without modifying the insertion loss in the pass band. A comparison of characteristics in filters is made when the combination of Defected Ground and Defected Microstrip Structures, as well as when only the first one are used. A model of the Defected Microstrip Structure and the corresponding equations to obtain the equivalent lumped and distributed element values are also given.

The modified finite-difference time-domain (M-FDTD) method is proposed to analysis electromagnetic bandgap of 1D layered anisotropic plasma photonic crystal(PPC) under the situa-tion of the EM wave oblique incidence. The presence of it avoids the usage of two-dimensional FDTD iterative and greatly improving the computational efficiency. By the algorithm, the reflec-tion coefficients of electromagnetic waves with different incidence angles are computed, and compare the results with the analytical solution. The results show that the method of the accuracy and effectiveness. Finally, the algorithm is applied to calculate electromagnetic bandgap charater-istics of PPC with the different incident angles, and their reflection coefficients under the condi-tion of the different incident angles are analyzed.

Confocal Microwave Imaging (CMI) for the early detection of breast cancer is based on several assumptions regarding the dielectric properties of normal and malignant breast tissue. One of these assumptions is that the breast is primarily dielectrically homogeneous, and that the propagation, attenuation and phase characteristics of normal breast tissue allows for the constructive addition of the UWB returns from dielectric scatterers within the breast. However, recent studies by Lazebnik et al. have highlighted a very signicant dielectric contrast between normal adipose and broglandular tissue within the breast. This dielectric heterogeneity presents a considerably more challenging imaging scenario, where constructive addition of the UWB returns, and therefore tumor detection, is much more dicult. In a dielectrically homogeneous breast, each additional beamformed backscattered signal adds coherently with existing signals, resulting in an improved image of any dielectric scatterers present. However, in a dielectrically heterogeneous breast, signals with a longer propagation distance are more likely to encounter heterogeneity and therefore are more prone to incoherent addition, reducing the overall quality of the breast image. In this paper, a novel beamforming algorithm is described, which gives extra weighting to signals with shorter propagation distances to create an improved image of the breast. The beamformer is shown to provide improved images of more dielectrically heterogeneous breasts than the traditional delay and sum beamformer from which it is derived.

The novel characteristics of wave transmission and reflection in one-dimensional semi-infinite chiral photonics have been investigated theoretically. Waves in each region have been formulated for both normal and oblique incidences. At a given incident angle, the transmission or reflection is found to be easily adjusted to be equal to 1 for the chiral photonics using chiral nihility media. The wave tunneling and rejection properties in chiral nihility photonics, as well as their parametric dependences on periodicity, chiral nihility and incident angles, have been explicitly presented theoretically and verified numerically.

A novel fractal antenna-array type is proposed. The design is based on the Sierpinski rectangular carpet concept. However, the generator is a circular ring area, filled with radiating elements, so the higher stages of the fractal development produce large arrays of circular rings which, besides the high directivity, have the advantage of the almost uniform azimuthal radiation pattern, attribute that many applications require. The introduced arrays can operate as direct radiating multi-beam phased arrays and meet the requirements of satellite communications links: high End of Coverage (EOC) directivity, low Side Lobe Level (SLL) and high Career to Interference ratio (C/I). These operational indices were further optimized by a synthesized multi-objective and multi-dimensional Genetic Algorithm (GA) which, additionally, gave arrays no more than 120 elements.

In this paper, an analytical method to characterize the frequency behaviour of Composite Right/Left Handed (CRLH) loaded printed dipole antenna is presented. One needs to determine the parameters of ungrounded reactive components realizing CRLH structures. Efficient resonant RLC circuit models based on Partial Elements Theory are presented to calculate inductance of meander line inductor and inter digital capacitor, while their capacitance is determined by Conformal Mapping Method. By using these circuit models and dispersion relation of balanced CRLH TL, negative resonance modes of antenna can be obtained. In addition, to validate the accuracy of the proposed analytical method, a prototype of the CRLH loaded printed dipole antenna is simulated, fabricated and measured.

In homeland security and law enforcement situations, it is often required to remotely detect human targets obscured by walls and barriers. In particular, we are specifically interested in scenarios that involve a human whose torso is stationary. We propose a technique to detect and characterize activity associated with a stationary human in through-the-wall scenarios using a Doppler radar system. The presence of stationary humans is identified by detecting Doppler signatures resulting from breathing, and movement of the human arm and wrist. The irregular, transient, non-uniform, and non-stationary nature of human activity presents a number of challenges in extracting and classifying Doppler signatures from the signal. These are addressed using bio-mechanical human arm movement models and the empirical mode decomposition (EMD) algorithm for Doppler feature extraction. Experimental results demonstrate the effectiveness of our approach to extract Doppler signatures corresponding to human activity through walls using a 750-MHz Doppler radar system.

We introduce a new slot resonator in the ground plane of a microstrip that is loaded with a parallel plate capacitor. The loaded slot has a 73% reduced length. Its unloaded Q-factor is 98 which is 91% higher than that of an ordinary slot. It is suitable to reject the narrow band unwanted signal. The proposed high Q-factor compact slot resonator also suppresses the undesired spurious high frequency response of the unloaded slot resonator. The structure is further used to determine the unknown dielectric constant of a sheet material with 0.04 variation in ε_r.

The Complete Complementary Sequence (CC-S) consists of several complementary orthogonal sequences and has optimal sidelobe level performance, which is satisfied with the requirement of the orthogonal Multiple Input Multiple Output (MIMO) radar signals. Aimed at the difficulty of high sidelobe level in Synthetic Aperture Radar (SAR) imaging processing in range dimension, an approach of depressing sidelobe level based on CC-S in MIMO SAR system was proposed. The transmitter model for orthogonal MIMO SAR system using CC-S and the corresponding matched filter (MF) were established in this paper. In addition, the MIMO SAR imaging results were simulated. The simulation results demonstrate that the performance of CC-S employed in orthogonal MIMO radar system is much better than that with traditional Linear Frequency Modulation (LFM) signal, by which the feasibility and validity of CC-S applied in orthogonal MIMO SAR system are justified.

Here we report a prism made of stacked quasi-selfcomplementary extraordinary transmission surfaces which allows simultaneously left- and right-handed propagation within the V-band for vertical and horizontal polarizations, respectively and righthanded propagation within the W-band for both polarizations. The numerical dispersion diagram of the infinite structure and effective indexes of refraction retrieved from S-parameters under normal incidence together with the finite integration time domain simulations predict single negative and double positive birefringence. The unusual type of birefringence single negative and regular double positive birefringence are afterwards demonstrated experimentally at the millimeter-waves (V- and W-bands) by the wedge experiment which lets us check, using a straightforward geometrical method, the refraction of each component. The effective index of refraction is retrieved via the Snell's law and compared to those obtained through the dispersion diagram and the retrieval method from S-parameters computed with the commercial software CST Microwave StudioTM^TM.