Adnan Affandi

Transmission Control of Electromagnetic Waves by Using Quarter-Wave Plate and Half-Wave Plate All-Dielectric Metasurfaces Based on Elliptic Dielectric Resonators

We present the design of all-dielectric Quarter-Wave Plate (QWP) and Half-Wave Plate (HWP) metasurfaces based on elliptic dielectric resonators (EDRs) for the transmission control of electromagnetic waves over the frequency band 20–30 GHz. First, an extensive numerical analysis was realized by studying the effect of the resonators geometry (thickness and ellipticity) on the transmission of both - and -polarized waves. Then, based on the numerical analysis, we have realized and characterized experimentally both QWP and HWP all-dielectric metasurfaces.

On Modelling and Comparative Study of LMS and RLS Algorithms for Synthesis of MSA

This paper deals with analytical modelling of microstrip patch antenna MSA by means of artificial neural network ANN using least mean square LMS and recursive least square RLS algorithms. Our contribution in this work is twofold. We initially provide a tutorial-like exposition for the design aspects of MSA and for the analytical framework of the two algorithms while our second aim is to take advantage of high nonlinearity of MSA to compare the effectiveness of LMS and that of RLS algorithms. We investigate the two algorithms by using gradient decent optimization in the context of radial basis function RBF of ANN. The proposed analysis is based on both static and adaptive spread factor. We model the forward side or synthesis of MSA by means of worked examples and simulations. Contour plots, 3D depictions, and Tableau presentations provide a comprehensive comparison of the two algorithms. Our findings point to higher accuracies in approximation for synthesis of MSA using RLS algorithm as compared with that of LMS approach; however the computational complexity increases in the former case.

Compact microstrip lowpass filter with ultra-wide rejection-band

A lowpass filter with wideband stopband is developed using microstrip line and proposed in this paper. It consists of shunt stepped-impedance open-circuited stubs and unit elements. The electrical length of the open-circuited stubs is chosen to be twice the length of the unit elements at a specific frequency. As a result, the filter can exhibit additional transmission zeros inside the rejection band and close to the cut-off frequency. Hence, the filter can provide an equal ripple performance with very high selectivity. The proposed design is verified by EM-simulations and experiment. A good agreement is attained between the calculated, simulated and measured results. The measured filter shows excellent performance with an extended stopband.

Circular Polarized Carbon-NanotubePatch Antenna embedded in Superstrates Anisotropic Media

The current distribution on surface of the Patch Antenna is radiating in the presence of the Superstrates layered anisotropic medium. The electric and magnetic field in the upper half-space are formulated using Dyadic Green Function in terms of Sommerfeld-Weyl-type integrals. The stationary phase method is used to obtain far-field expressions. Carbon-Nanotube Composite (CNT) as the radiating element for Star Patch Antenna is used. .Return loss, Axial Ratio ( <3 dB Circular Polarized), Gain and Directivity parameters of Carbon-Nanotube Star Patch Antenna are compared for different anisotropic materials.

An accurate six-port microstrip reflectometer

This paper describes the properties of a novel 8-port coupler which has been assembled out of three 4-port interdigitated couplers. The procedures used in the design of this coupler, as well as in the derivation of its essential parameters are demonstrated. The scattering matrix of the proposed coupler is derived by using the signal flow graph (SFG) technique. The 8-port coupler has been modified with proper terminations in order to produce a working six-port reflectometer. Detailed SFG analysis of this reflectometer reveals that it is inherently of a broad-band character. This reflectometer has been fabricated, calibrated and tested at the X band.