Electromagnetic scattering at high-frequencies is computationally heavy. Radar cross section (RCS) of electrically large concave and convex objects are solved by using the hybrid method. For convex and concave surfaces, Modified-Vector Physical Optics (MPO) with enhanced accuracy and Iterative Physical Optics (IPO) taking multiple-reflections into account, are selectively and independently applied for convex and concave parts of the scatterer. The accuracy of RCS by this hybrid method is tested with the MoM based simulator Wipl-D as the reference. The RCS from relatively small scatterers with the dimension of the order of a few wavelengths can be successfully predicted.

Locality of high frequency electromagnetic scattering phenomena is embodied and imported to the Method of Moments (MoM) to reduce computational load. The proposed method solves currents on small areas only around inner and edge stationary phase points (SPPs) on the scatterer surfaces. The range of MoM area is explicitly specified in terms of Fresnel zone number as a function of frequency, source and observer positions. Based upon this criterion, scatterer of arbitrary size and shape can be solved with almost frequency independent number of unknowns. In some special cases like focusing systems, locality disappears and the method reduces to the standard MoM. The hybrid method called PO-MoM is complementarily introduced to cope with these cases, where Fresnel zone number with analogous but different definition is used. The selective use of Local-MoM and PO-MoM provides frequency insensitive number of unknowns for general combination of source and observation points. Numerical examples of RCS calculation for two dimensional flat and curved surfaces are presented to demonstrate the accuracy and reduction of unknowns of this method. The Fresnel zone, introduced in the scattering analysis for the first time, is a useful indicator of the locality or the boundary for MoM areas.

The effect of wall and indoor scatterers on the indoor multiple input multiple output (MIMO) communication system is investigated by using the hybrid technique of finite difference time domain (FDTD) method and method of moments (MoM). MIMO channel capacity with the wall reflection is investigated with consideration of the eigenvalue of channel covariance matrix, the received power and the effective multipaths of MIMO system. It is found that the stronger side wall reflection can lead to the higher MIMO channel capacity. MIMO system with indoor scatterers is also analyzed and compared with the line of sight (LOS) indoor MIMO system. It is found that the scatterer material has different effect on the received power and the effective multipaths of MIMO system.

A numerical hybrid method for analyzing the wireless channel of Multiple-Input Multiple-Output (MIMO) communication system is proposed by combining of the method of moments (MoM) and the finite difference time domain (FDTD) method. The proposed method is capable of investigating a more practical MIMO wireless channel than the conventional methods, and CPU time is much less than that of the FDTD method in analysis of spatial statistical characteristics of received signals. Based on the channel transfer matrix obtained by the proposed method, the wall effect on indoor MIMO channel capacity are investigated with consideration of received power, Ricean K-factor and effective degrees of freedom (EDOF) of multipaths by changing the wall locations and material.

Existing vision substitute systems have insufficient spatial resolution to provide environmental information. To present detailed spatial information, we propose two stimulation methods to enhance transfer information using a 2-D tactile stimulator array. First, stimulators are divided into several groups. Since each stimulator group is activated alternately, the interval of stimulations can be shortened to less than the two-point discrimination threshold. In the case that stimulators are divided into two and four groups, the number of stimulators increases to twice and four times, respectively, that in the case of the two-point discrimination threshold. Further, a user selects the measurement range and the system presents targets within the range. The user acquires spatial information of the entire measurement area by changing the measurement range. This method can accurately present a range of targets. We examine and confirm these methods experimentally.

The effects of wall reflection on indoor MIMO channel capacity are statistically investigated with consideration of the average received power, the effective degrees of freedom (EDOF) of multipaths and the eigenvalues of transfer channel covariance matrix. It is found that the stronger wall reflection can lead to higher MIMO channel capacity.

Effects of wall material on the channel capacity of an indoor multiple input multiple output (MIMO) system are investigated using a hybrid technique of the method of moments (MoM) and the finite difference time domain (FDTD) method with consideration of the Ricean K factor and the effective degrees of freedom (EDOF) of multiple paths.

This paper presents a hybrid technique combining the mode-matching method and moment method to analyze various slots cut in the wall of a rectangular waveguide partially filled with a dielectric slab. The waveguide slot structure is decomposed into two parts: a dielectric-loaded waveguide T-junction and an open-ended waveguide radiating into half space. The T-junction is analyzed by the mode-matching method, while the open-ended waveguide is characterized by the moment method with the modal functions in the slot being the full domain basis functions. A new approach for computing multidimensional integrals is proposed in the formulation of the open-ended waveguide, which greatly reduces the computation effort. The T-junction and the open-ended waveguide are then cascaded to obtain the final scattering parameters of the slot structure. Numerical results for different slots on a dielectric-loaded rectangular waveguide calculated by the hybrid method are presented and validated by comparing with measured and simulated data by Ansoft's HFSS. Good agreement is observed for all the cases considered. Parametrical studies are also conducted to examine the effect of the dielectric slab's thickness and relative permittivity on slot antenna's impedance/admittance.

A new hybrid formulation has been derived for analyzing biological electromagnetic compatibility (Bio-EMC) problems by combining the frequency-domain Method of Moments (MoM) and the Finite-Difference Time-Domain (FDTD) method. This hybrid form is different from, and more direct than, the method previously proposed by Mangoud et al. Some numerical examples are given for the human head exposure field due to a half wavelength dipole and a one-wavelength loop antenna. Our iterative method is found to have fast convergence. In addition, our method works well for cases when the radiation antenna wires are not aligned with the FDTD lattice.

This paper shows a comparison between several procedures to represent the Physical Optics (PO) current density into a hybrid Moment-Method-Physical-Optics (MM-PO) code. Some numerical results demonstrate that a set of basis functions suitable for the Method of Moments (MM) may be inappropriate to model the PO currents. A new evaluation of the PO operator is proposed. The radiation can be analytically determined and, since it includes a linear interpolation of the phase, it can be applied over large triangular domains. This allows a drastic reduction of the computational cost, maintaining or even improving the level of accuracy.

Power exponentiation is an important operation in modern cryptography. This operation can be efficiently calculated using the concept of the addition chain. In this paper, two new systematic methods, a Run-length method and a Hybrid method, are proposed to generate a short addition chain. The performance of these two methods are theoretically analyzed and it is shown that the Hybrid method is more efficient and practical than known methods. The proposed methods can reduce the addition chain length by 8%, in the best case, compared to the Window method.