In this paper, a novel nano antenna with two radiation modes is introduced. The structure of this nano antenna consists of a ring coupler and two patch antennas placed on a SiO2 substrate. The direction of the main lobe of the radiation pattern of this nano antenna can be adjusted to be either in the broadside or the endfire direction. The proposed nano antenna is optimized to minimize the losses and to maximize the radiation efficiency in addition to achieve maximum discrimination between the two desired directions of the main beam. In optimizing the proposed structure, the computationally expensive full-wave electromagnetic simulation is replaced by cheaper surrogate models, which are kriging models. Two optimization techniques, namely multi-objective particle swarm with PROMETHEE method and design centering using the normed distances, are used to obtain the optimal values of the design parameters. A convergence test is performed to ensure the validity of the obtained simulation results. A sensitivity analysis is performed to show how the manufacturing tolerance in each design parameter is affecting the performance of the proposed nano antenna.

In this paper, a comprehensive integral equation formulation of plasmonic transmission lines is presented for the first time. Such lines are made up of a number of metallic strips with arbitrary shapes and dimensions immersed within a stack of planar dielectric or metallic layers. These lines support a number of propagating modes. Each mode has its own phase constant, attenuation constant, and field distribution. The presented integral equation formulation is solved using the Method of Moments (MoM). It provides all the propagation characteristics of the modes. The new formulation is applied to a number of plasmonic transmission lines, such as: single rectangular strip, horizontally coupled strips, vertically coupled strips, triangular strip, and circular strip. The numerical study is performed in the frequency (wavelength) range of 150-450 THz (0.66-2.0 μm). The results of the proposed technique are compared with those obtained using Lumerical mode solution, and CST. Very good agreement has been observed. The main advantage of the MoM is its intrinsic speed for this type of problem compared to general purpose solvers.

In this paper, new models based on an artificial neural network (ANN) are developed to predict the propagation characteristics of plasmonic nanostrip and coupled nanostrips transmission lines. The trained ANNs are capable of providing the required propagation characteristics with good accuracy and almost instantaneously. The nonlinear mapping performed by the trained ANNs is written as closed-form expressions, which facilitate the direct use of the results obtained in this research. The propagation characteristics of the investigated transmission lines include the effective refractive index and the characteristic impedance. The time needed to simulate 1000 different versions of the transmission line structure is about 48 h, using a full-wave electromagnetic solver compared to 3 s using the developed ANN model.

This article introduces a new RFID tag antenna designed for operation at 915 MHz. The proposed antenna is electrically small with dimensions (λ₀/15) × (λ₀/15). It features two vivaldi-like apertures flipped with respect to each other around an axis parallel to their slotted edges. Each aperture is loaded with a meander line with multiple loops. The two sides of the proposed antenna are fed via a common slot line that is coupled electromagnetically to a perpendicular microstrip line at the other side of a dielectric substrate. The new antenna are fabricated using printed circuit board technology and the fabricated prototype is experimentally characterized. The optimization and theoretical investigation of the proposed antenna are performed via both HFSS and CST. The two simulators agree very well with each other and with measurements. The characteristics of the new RFID antenna are generally good, such as: small size (22 mm²), low profile (0.8 mm), flexible impedance matching, reasonable impedance bandwidth (8%), omni-directional radiation, low cross-polarization level (−20 dB at broadside), acceptable radiation efficiency (76%), and gain (−0.3 dBi). © 2012 Wiley Periodicals, Inc. Int J RF and Microwave CAE 23: 639–645, 2013.

A new circularly polarized wire-grid nano-antenna array designed for optical telecommunication applications is proposed in this paper. The array consists of two groups of radiators, which are orthogonal to each other. Each group consists of six aligned radiators connected via nonradiating connectors. A 90° phase shift is achieved by inserting a gap between the feeding coupling rods and the inner radiators of one of the two antenna groups. The antenna is characterized by its high directivity (10.8 dBi) and a wide axial ratio bandwidth, which covers the range from 188.2 to 197.8 THz. The radiation efficiency of the antenna is 82.75% at 193.55 THz with very small variations along its operating bandwidth. Such good radiation characteristics are very attractive for optical communication applications.