In order to obtain a unified approach for the Finite-Difference Time-Domain (FDTD) analysis of dispersive media described by a variety of models, the coordinate stretched Maxwell's curl equation in time domain is firstly deduced. Then the FDTD update formulas combined with the semi-analytical recursive convolution (SARC) in Digital Signal Process (DSP) technique for general dispersive media are obtained. In this method, the flexibility of FDTD in dealing with complicated object is retained; the advantages of absolute stability, high accuracy, less storage and high effectiveness of SARC in treating the linear system problem are introduced, and a more unified update formulation for a variety of dispersion media model including Convolution Perfectly Matched Layers (CPML) absorbing boundary is possessed. Therefore it can be applied to analysis of general dispersive media provided that the poles and corresponding residues in dispersive medium model of interest are given. Finally, three typical kinds of dispersive model, i.e. Debye, Drude and Lorentz medium are tested to demonstrate the feasibility of presented approach.

In this paper, the design, simulation, and fabrication of a novel printed circular slot antenna with a band-notched function suitable for UWB application is presented and investigated. The band-notched characteristic is achieved and adjusted by inserting L-shaped branches into the ground plane. Experimental results show that the proposed antenna meets the requirement of wide working bandwidth of 3.1-10.6 GHz with return loss < -10 dB, while avoiding the interference with the 5-GHz WLAN band. The study of transfer function (amplitude of S₂₁/group delay) and time domain characteristic (fidelity/power spectrum density (PSD)) indicate a band-notched function of the antenna. The proposed antenna has a compact size, good radiation characteristics, ultra wide band-width, and good time-domain behaviors to satisfy the requirement of the current wireless communication systems.

In this paper, one 3×3 and one 5×5 antenna arrays are studied. In each array, one probe-fed circularly polarized (CP) microstrip patch antenna is placed at the center as the driven antenna and is gapped coupled to the remaining elements. It is investigated that CP performance of the patch can be proved by properly arranging these parasitic elements. The driven patch is a perturbed square one with two diagonal corners truncated. The remaining elements are square patches slightly smaller than the driven patch. The proposed antennas have been constructed and measured. The 3×3 array has a measured gain of 7.7 dBic with a 3 dB axial ratio bandwidth of 3.3%. The 5×5 array has a measured gain of 9.3 dBic with a 3dB axial ratio bandwidth of 8.1%.

A novel triple-mode hexagonal bandpass filter with capacitive loading stubs is introduced in this article. The technique, adding an open capacitive stub, is applied to enlarge the equivalent self-capacitance of the resonator, which declines its resonant frequencies. Three radial-line stubs in the center of top layer are used to implement this technique. One mode resonant frequency is varied with the radii of three radial-line stubs, while the other two modes are nearly not affected. This filter has a pair of transmission zeros which are close to the passband, thus it behaves with high selectivity. For method validation, a bandpass filter operating at 2.4 GHz is fabricated and measured. The experimental results are demonstrated and discussed.

A compact dual-band power divider for GSM/DCS applications is proposed in this letter. Novel planar artificial transmission lines are applied to miniaturize the power divider and achieve wideband response. The proposed dual-band power divider is about 37% of conventional one. The design principle, simulated and measured results are all discussed. The measured results show that good performance can be achieved at the operation frequencies.

Fractional rectangular impedance waveguide has been studied using fractional curl operator. Behavior of field inside the fractional rectangular impedance waveguide has been studied with respect to the original impedance of walls of the guide as well as fractional parameter. Analysis of the impedance of the walls as well as power distribution over the cross sectional plane of fractional impedance rectangular waveguide has been given. It has been found that fractional curl can be used to control the power distribution pattern over the cross sectional plane.

A novel wideband multilayered microstrip antennas with shorting pins and arc-shaped apertures loaded is designed and fabricated. The antenna consists of two dielectric substrates and a quasi H-shaped circular patch with five shorting pins and four arc-shaped apertures loaded on the upper layer. Multiple layers are employed to achieve wide bandwidth by stacked electromagnetic coupling. The arc-shaped apertures and shorting pins are used to excite multiple modes, which can change the cavity's electromagnetism characteristic with influencing the series-parallel connection inductance, so that the wide bandwidth is obtained. Effects of the key parameters on the wideband performance are also studied, and a set of optimum values is chosen for the antenna design. The impedance bandwidth (VSWR < 2.0) of the proposed antenna reaches 2.59 GHz with the measured results, which means the relative impedance bandwidth is expanded up to 34.7% across 6.17 to 8.76 GHz. Simulation results agree well with measured ones.

A novel scheme of combining non-uniform rational B-splines (NURBS) model with higher-order moment method (HOMM) is presented. The mesh precision of conforming to practical object is a major factor for HOMM to yield accurate results. In the present paper, NURBS technique is employed to model complex objects accurately with large curved Bezier patches and no factitious geometric discontinuities are introduced between the adjoining patches. The higher-order modified Legendre basis functions are defined on Bezier patch. As a result of the combination of NURBS model with HOMM, the accuracy of results is greatly improved compared with HOMM on curved parametric quadrilateral (CPQ) model, meanwhile, the number of unknowns is much reduced. Numerical results show that NURBS-HOMM is an efficient technique with good potential to solve the electromagnetic (EM) problems of complex electrically large objects.

Magnetic near-field scanning is a growing-up technique in power electronics. However, due to the large size of the devices, a trade-off is necessary to find between the spatial resolution of the field and the measurement time, this one is often unsatisfying. In this paper, we propose to improve drastically this trade-off by using a signal-processing technique (Wiener filtering) which allows a large scanning step (short scanning duration) while keeping an accurate spatial resolution of the magnetic field. This technique is adapted to the magnetic near-field probing, as described in the paper. Our experiments show that a factor 25 can be gained on the product "resolution-×-duration" of the measurements.

A compact CPW-fed slot antenna is proposed for dual-band wireless local area network (WLAN) operations. In this letter, electromagnetic band gap (EBG) structures with square-shaped lattices have been incorporated into the feed network for harmonic suppression. Experimental results show that EBG structures not only exhibit well-behaved band stop characteristics, but also enhance the bandwidth of the proposed antennas. For the proposed antenna with square-shaped lattices, the -10 dB return loss bandwidth could reach about 38.4% for the 2.4 GHz band and 23.8% for the 5 GHz band, which meet the required bandwidth specification of 2.4/5 GHz WLAN standard.

ℜThis paper presents a dimensional synthesis method for designing wide-band quarter-wavelength resonator bandpass filters. In this synthesis method, an alternative lowpass prototype filter and the edge frequency mapping method are proposed and applied. The improved K- and J-inverter model with the exponent- weighted turns ratio is also proposed in order to incorporate the frequency dependence of inverters. Based on the edge frequency mapping method and the improved inverter model, an iterative dimensional synthesis procedure is then presented. As design examples, a four-pole rectangular coaxial bandpass filter with 63% fractional bandwidth is designed and fabricated. The simulation and measurement results show good equal ripple performance in the passband.

We present a new approach to the modeling of angle and time of arrival statistics for radio propagation in typical office buildings, in which the majority of interior scattering objects are either parallel or perpendicular to the exterior walls. We first describe the reradiating elements in office buildings as randomly distributed arrays of thin strips. The amount of clutter and the amount of transmission/reflection loss are then accounted for through several key parameters of the site-specific features of indoor environment, such as the layout and materials of the building under consideration. Subsequently, the important channel parameters including power azimuthal spectrum (PAS) and power delay spectrum (PDS) are derived. An appealing observation is that when the path angles from multiple channel trials are measured and collectively analyzed, deterministic angle clustering becomes evident. This phenomenon agrees well with the existing ray-tracing (RT) results reported by Jo et al. in buildings of this type and cannot be explained by other geometric channel models (GCMs). Furthermore, the proposed model predicts an asymmetric cluster PAS for a single-channel-trial scenario, which yields an excellent fit to the experimental data presented by Poon and Ho. Finally, we have also investigated the behaviors of the superimposed PAS and PDS under various channel conditions.

We propose a novel UWB bandpass filter (BPF) design using the suspended stripline (SSL). The filter composes of a lowpass and a high-pass circuit, both implemented by SSL structures. A notch response structure might be implemented to the filter by embedding a resonant slotline. The quasi-lumped elements circuit models were developed to analyze these circuits' performance. Experiments were conducted, and good agreements were observed between the measurements and simulations.

A theoretical model of scattering from three-dimensional arbitrary layered media with 3D infinite rough surfaces based on the small perturbation method (SPM) is derived in the present paper. The scattering field and bistatic scattering coe±cient for linear polarized waves are derived respectively. Firstly, the electric and magnetic fields in each region of the layered structure are expanded into perturbation series in spectral domain. Secondly, the expansion coefficients of each order are obtained by applying the boundary conditions. As a result, the expressions of the zeroth-, first- and second-order solutions of the scattering problem based on the SPM are obtained, in which the second-order solution is the primary contribution of this work. The theoretical model is helpful to understand the dependence between the scattering field and physical properties of the layered structure (such as surface roughness and dielectric constants at different depths). The result can be applied to modeling of the received radar signal from nature targets such as layered soil and ice with full polarizations.

In this paper, accelerated techniques for three dimensional ray tracing using the concept of ray frustums are presented for the fast characterization of wireless communications, where various radio propagation paths such as wall-transmitted wave and scattered wave from buildings and ground are generated. To accommodate such scatterers, objects are modeled by triangulated meshes, and potential ray paths are searched and stored in the form of ray frustums. The presented acceleration techniques using the frustums include sorting of triangulated surfaces, hashing functions and space partitioning. The validity of the method is verified by comparison with measurement data.

Aimed at improving the radiating characteristics (pattern and polarization) and simplifying the design of feeding network, a new approach is applied and discussed. For uniformly excited planar antenna array, by rotating each element in its local coordinates and determining the rotation angles of the elements, the 3D radiating characteristic of the planar antenna array can be improved. The Differential Evolution (DE) algorithm is applied for optimizing rotation angles of the elements. Furthermore, the effects of the elements rotation are discussed in detail.

A novel approach of left-handed (LH) structures is introduced to reduce the size of microwave components by combining a loaded coupled transmission lines and complementary split ring resonators (CSRRs). The performance of the loaded part of the proposed model is equal by two cascaded unit elements. The equivalent circuit model and subsequently, the left and right handed transmission frequencies of the proposed structure are presented. A highly miniaturized dual-band branch-line coupler (BLC) is analyzed, designed, tested and proposed by this technique. The size reduction is reported about 75% in analogy with the conventional ones. The measurement results are in good agreement with the theoretical ones.

In recent years, Computer Aided Design (CAD) based on Artificial Neural Networks (ANNs) have been introduced for microwave modeling, simulation and optimization. In this paper, the characteristic parameters of edge coupled and conductor-backed edge coupled Coplanar Waveguides have been determined with the use of ANN model. Eight learning algorithms, Levenberg-Marquart (LM), Bayesian Regularization (BR), Quasi-Newton (QN), Scaled Conjugate Gradient (SCG), Conjugate Gradient of Fletcher-Powell (CGF), Resilient Propagation (RP), Conjugate Gradient back- propagation with Polak-Ribiere (CGP) and Gradient Descent (GD) are used to train the Multi- Layer Perceptron Neural Networks (MLPNNs). The results of neural models presented in this paper are compared with the results of Conformal Mapping Technique (CMT). The neural results are in very good agreement with the CMT results. When the performances of neural models are compared with each other, the best results are obtained from the neural networks trained by LM and BR algorithms.

The design and performance of a stacked patch antenna for wideband and dual-frequency operation are presented in this paper. The proposed antenna consists of a three dimensional (3D) circular transition-fed patch that is excited by a coaxial probe. By introducing a regular patch and a ring patch above the 3D circular transition-fed patch, good input impedance matching has been achieved over two frequency bands. The lower band possesses an impedance bandwidth (VSWR < 2) of 22.8% (0.775 to 0.975 GHz) and a peak gain of 5.2 dBi, while the upper band has an impedance bandwidth (VSWR < 2) of 65.8% (1.425 to 2.825 GHz) and a peak gain of 7.4 dBi. Other than the wideband and dual-band operation features, this antenna also has a beam tilted downward with a broadside beam pattern on the horizontal plane. Therefore, this antenna is very suitable for the indoor base station that is required to service several wireless communication systems, included CDMA800, GSM900, 3G, PCS, UMTS, BLUETOOTH and WLAN, by a single antenna.

This paper presents a realization of composite right/left handed transmission lines using coupled microstrip lines. This structure exploits the advantages of the microstrip lines, while increases the coupling by a floating conductor at the ground plane. The performance of this composite right/left-handed line is demonstrated by both simulated and measured results, and they show good agreement. The designed line has broad bandwidth with low losses and small size. A novel dominant mode leaky wave antenna design, using the previous structure, is presented with backward to forward scanning capability.