H. A. Elmikati

B15. Tri-band slotted bow-tie antenna design for RFID reader using hybrid CFO-NM algorithm

In this article, a dual bow-tie slot antenna for 915/2450/5800 MHz triple band RFID applications is presented. The size of the proposed antenna is determined by the middle resonant frequency. The lower and upper operating frequencies are obtained by inserting metal strip pairs near the ends of the slotted dual bow-tie without increasing the overall antenna area. The hybrid approach involving Central Force Optimization and Nelder-Mead (CFO-NM) algorithm is considered to optimize the antenna dimensions. The CFO-NM algorithm program was implemented using MATLAB-software which linked to the CST Microwave studio software to simulate the antenna. In addition the optimized antenna is simulated by the Finite Difference Time Domain (FDTD) method to validate the results.

B16. Effect of mutual coupling on the performance of four elements microstrip antenna array fed by a Butler matrix

Detailed design of a four element microstrip antenna array fed by a Butler matrix is presented. The proposed structure represents a switched-beam smart antenna system working in the ISM band at 2.45 GHz. To compensate for mutual coupling effects, a four-arm spiral electromagnetic bandgap (EBG) structure is inserted between adjacent microstrip patches. The four-arm spiral EBG structure provides 40% reduction in size compared with the conventional mushroom EBG structure. The antenna gain with and without EBG substrate is evaluated taking into account the effect of mutual coupling. It is found that the use of four-arm spiral EBG substrate reduces the mutual coupling by (3-17) dB between the patches. This is useful in improving the accuracy of the direction of the main beam of the array. Moreover, this improves the gain by a small value of 0.25 dB. Simulation of the antenna system is carried out using Ansoft Designer software V4.

Novel symmetric hierarchical mixed finite element analysis for nanophotonic devices

A Novel symmetric mixed finite element is introduced for the accurate modal analysis of optical waveguides and photonic devices. In addition to the advantages of conventional curl conforming mixed finite elements, the proposed element is symmetric and hierarchical. Symmetry ensures that the solution accuracy is not dependent on the shape functions chosen. On the other hand, hierarchy property allows p-adaptation that enables the use of elements with different orders in the same mesh which makes it very efficient. The numerical results show the effectiveness of the proposed element in modelling optical waveguides and other important photonic structures such as silicon nanowires and hybrid dielectric plasmonic waveguides.

Implementation of Photonic Crystal Couplers

Finite Difference Time Domain (FDTD) analysis is effectively applied to investigate the transmission of the transverse electric polarized pulses in a 90deg bend photonic crystal waveguide. A comparison with a Time Domain Beam Propagation Method (BPM) based on finite clement scheme is made and excellent agreement is achieved. Moreover, a detailed study of photonic crystal couplers has been carried out. A series of simulations are performed to determine by how much the radius of holes would have to be tuned to result in realizing the functions of the truth tables of the proposed optical directional couplers.

Slotted bow-tie antenna design for RFID readers using hybrid optimization techniques

Recently hybrid optimizations algorithm has attracted a lot of attention as a high-performance optimizer. This paper presents a comparison between different hybrid optimization algorithms. The proposed algorithms are used to design a slotted bow-tie antenna for 2.45 GHz Radio Frequency Identification (RFID) readers. The antenna is optimized using different algorithms integrated with the CST Microwave studio. Four algorithms are compared: Genetic Algorithm (GA), Particle Swarm Optimization (PSO), hybrid approach involving Genetic Algorithm (GA) and Nelder-Mead (NM) algorithm (GA-NM), and a hybrid approach involving PSO and Nelder-Mead optimization algorithm (PSO-NM). It is anticipated that the introduced hybrid approaches are more efficient and can be applied to other types of antennas.

FDTD analysis of a rectangular patch antenna on a general uniaxial anisotropic dielectric substrate

The problem of a rectangular microstrip patch antenna on arbitrary anisotropic dielectric substrate is treated. The finite-difference time-domain (FDTD) method with perfectly matched layer absorber (PML) is applied to determine the time domain field response, the return loss, the input impedance and the radiation pattern of the proposed structure. In addition, the effect of feeder displacement is studied. The results obtained by the FDTD with PML are found to be in good agreement with the published data.

FDTD analysis of patch antenna over a multi-layer substrate

In this paper, rectangular microstrip patch antenna over a multi-layer substrate configuration is presented. This patch antenna configuration improves the bandwidth and the radiation pattern of the patch. The finite-difference time-domain (FDTD) method with perfectly matched layer absorber (PML) as well as Murs (1981) first order absorbing boundary conditions (Murs FOC) is applied to determine the return loss, the effective dielectric constant, the input impedance and the radiation pattern of the proposed structure. In addition, the effect of changing the air gap layer thickness of that antenna is studied. The results obtained by the FDTD with PML are found to be in better agreement with the published measured data than those obtained by the FDTD with Murs FOC.

Compact polarization rotator based on SOI platform

A compact, easy-to-fabricate polarization rotator design based on silicon on insulator (SOI) platform is introduced and validated. Breaking the symmetry of the commonly used silicon nanowires, mode hybridness could be maximized until polarization rotation is achieved with a high efficiency. The reported asymmetric polarization rotator is very compact with length of only 4.62 μπι. It can achieve high conversion efficiency (> 97%) over a wide bandwidth (290 nm) centered around wavelength, λ, of 1.55 μm. The fabrication of the introduced polarization rotator is compatible with standard CMOS fabrication technologies which makes its fabrication a straight forward process.

Compact Ultra-Wideband monopole antenna design for wireless communication using differential evolution optimization algorithm

An internal Ultra-Wideband (UWB) monopole antenna for use in portable wireless communication applications is presented with a compact dimensions. It consists of a radiating patch, a matching stub, and a ground plane. The effect of defected ground plane structure (DGS) is studied in addition to the effect of defected slots in the radiating patch and matching stub on the return loss (S11). The Differential Evolution (DE) algorithm is considered to minimize S11 in the UWB frequency range by determining the appropriate antenna dimensions, the results are compared with other optimization techniques such as Genetic Algorithm (GA) and Particle Swarm Optimization (PSO). Also, the proposed antenna is built into a plastic case (εr = 3), having external dimensions 43.4 × 21.4 × 8.3 mm to study its effect on the radiation parameters.

A single layer training for high speed character recognition

Single-layer training for high speed English capital or small letters recognition is presented. A new approach to the hardware implementation of the artificial processing element (PE) and control circuits with learning is introduced. The programmable synaptic weights are computed during the training period by a software program. The proposed learning algorithm is very fast and significant in many ways. The results are computed in real time and appear to be perfect. This system is very suitable for analog-digital VLSI implementation.