Advanced Electromagnetics

Design and Characterization of a Compact Single Layer Modified S-Shaped Tag Antenna for UHF-RFID Applications

M. A. Ennasar, I. Aznabet, O. EL Mrabet, M. Essaaidi — Thu, 21 Mar 2019 16:46:00 -0400

In this paper, we report the design of a new compact single layer modified S-shaped tag antenna for UHF-RFID applications. To achieve a compact size of 51×34 mm² for this tag antenna, the technique of using S shaped strip is applied, and by further adding a pair of equilateral triangular stubs into this structure, good impedance matching can be obtained at 915 MHz, which is the center frequency of the North-American UHF-RFID band (902 to 928 MHz). Besides exhibiting acceptable 5m read range in free space at 915 MHz, the proposed design shows a read range of about 4.5 when mounted on a metallic object (200 ×30 cm²) separated by spacer foam of thickness 1 cm. Furthermore, the proposed design shows a reasonable read ranges when it is mounted on different dielectrics with low permittivity. The proposed design has a simple configuration, low cost, acceptable read range, and can work on various background materials.

Modeling a Planar Coupled Microstrip Lines using various Wavelets and Method of Moments

M. Bayjja, M. Moubadir, G. Alsharahi, M. Aghoutane, N. Amar Touhami — Wed, 20 Mar 2019 06:51:00 -0400

In this paper, we apply a several wavelets basis functions to the method of moments to modeling the parallel-coupled microstrip lines. The ﬁrst set of equations is for the shielded microstrip line solved with moment’s method and wavelets. The Green’s function is obtained from the theory of images. The second set are for the parallel-coupled microstrip lines operating in the TEM mode or when the analysis can be based on quasi-static approximation, the properties of coupled lines can be determined from the self- and mutual inductances and capacitances for the lines. To demonstrate the effectiveness and accuracy of the proposed technique, numerical results of even- and odd-mode characteristic impedances, coupling coefficient, percentage sparsity achieved in the impedance matrix, the CPU Time to reverse impedance matrix, and error relative for Daubechies, Coiflets, Biorthogonal and Symlets wavelets are presented. Numerical results are in good agreement with those in previous publications.

Lightning Response of Multi-Port Grids Buried in Dispersive Soils: An Approximation versus Full-wave Methods and Experiment

S. S. Sajjadi, S. R. Ostadzadeh — Tue, 19 Mar 2019 10:56:18 -0400

In this paper, application of multi-conductor transmission line model (MTL) in transient analysis of grounding grids buried in soils with frequency-dependent electrical parameters (dispersive soil) is investigated. In this modeling approach, each set of parallel conductors in the grounding grid is considered as a multi-conductor transmission line (MTL). Then, a two-port network for each set of parallel conductors in the grid is then defined. Finally, the two-port networks are interconnected depending upon the pattern of connections in the grid and its representative equations are then reduced. Via solving these simplified equations, the transient analyses of grounding grids is efficiently carried out. With the aim of validity, a number of examples previously published in literature are selected. The comparison of simulation results based on the MTL shows good agreement with numerical and experimental results. Moreover, in despite of numerical methods computational efficiency is considerably increased.

Design of a Polarization-Independent Dual-Band Electromagnetically Induced Transparency-Like Metamaterial

O. Demirkap, F. Bagci, A. E. Yilmaz, B. Akaoglu — Sun, 17 Mar 2019 17:20:47 -0400

In this study, the classical analog of single and dual-band electromagnetically induced transparency is demonstrated with a four-fold symmetric metamaterial consisting of a Minkowski fractal ring resonator surrounded by a square ring resonator. The proposed metamaterials show high transmission ratios at the polarization independent resonances, as confirmed by the applied two different numerical methods. Delay-bandwidth products are found to be 0.34 and 0.61 at the resonances of the dual-band metamaterial. The peak frequencies and transmission ratios maintain also for oblique angle of incidences. These features of the proposed metamaterials are promising for single and multi-band filtering applications as well as for slow light and sensing devices.

Artificial Chiral Media Using Conical-Coil Wire Inclusions

G. B. DeMartinis, D. Kalluri — Sun, 17 Mar 2019 16:37:43 -0400

The electromagnetic response of the electrically small conical wire coil as a chiral inclusion is described. An existing model of the helical coil wire inclusion is extended to model the conical coil wire inclusion, using the Method of Moments (MoM) to determine the dominant resonant circuit impedance of the inclusion. Material parameters are determined using mixing relations with polarizability coefficients expressed for the conical coil inclusion geometry. The polarization conversion of a dielectric slab loaded with conical coil inclusions is predicted and compared to simulated results using a forward scattering technique.

Improved Efficiency of Inductive Power Transfer in Misalignment Conditions with Multi Coil Design

P. B. Laksono, M. Alaydrus — Sun, 17 Mar 2019 15:04:30 -0400

In charging process of electric vehicle, a misalignment between the transmitter (Tx) and receiver (Rx) coupling structure decreases the efficiency of the wireless power transfer. In inductive power transfer system, misalignment reduces the effective coupling between the Tx and Rx coils. In this work, based on previous multiple coil structures, a new multi coil design in proposed to increase the efficiency of the power transfer. Here, a multi coil structure with two rectangular and four spiral coils is designed with the overall dimension of the coil structure 26.5 cm x 36.5 cm. The measurement shows, that for coil distance below 10.3 cm and a lateral misalignment of maximal 10 cm (27.4%), the efficiency of the designed multi coil structure is better compared to previous coil structures. However for larger coil distance or larger misalignment, the efficiency of the new coil structure deteriorates significantly.

On Effect of Planar Scaling on Microstrip Patch Antenna Performance

A. Esmaeilkhah, C. Ghobadi, J. Nourinia, M. Majidzadeh — Sun, 17 Mar 2019 14:44:07 -0400

This paper aims at investigating the effect of planar scaling on Microstrip patch antenna performance. To this end, nine antennas with different sizes are fabricated on the same FR4 substrate with thickness of 1mm with different scale factors. Results indicate some deviations between the obtained expected, simulated and measured resonant frequency which could be mainly due to the truncation error effect, and the SMA connector effect in the scaling process. All the influential factors are studied in detail through the paper. Detailed discussion on the scaling process and its effect on the antenna performance would be presented.

Wideband Microstrip Dipole Antenna Design for WLAN/WiMAX Applications

A. Sondas — Sun, 17 Mar 2019 13:36:26 -0400

Recently, microstrip antennas are preferred in all areas of wireless communication, due to their advantages such as low volume coverage, light weight, surface compatibility, high cost requirements and easy production etc. The main disadvantage of these antennas is their narrow band performance (~11%). In the literature, there are some wideband microstrip antenna designs. These broadband characteristics are obtained by changing the antenna geometry or by adding new parasitic patches to the antenna elements. In this study, a classical wideband microstrip dipole antenna (MDA) design which can be used in WLAN/WiMAX applications (covering the bands
2.4–2.5 GHz and 2.5–3.5 GHz) is introduced. The proposed antenna has a pair of twisted strip which are placed asymmetrically near the feed of the dipole element with a length of 52 mm (~λ/2). Also a pair of square loop elements is placed on a sublayer. The proposed MDA has a resonance between 2.06-3.72 GHz with a bandwidth of 57%. The antenna has a directive radiation pattern with a gain of 6.49-3.98 dBi.

An Inverse Scattering Approach Based on Inhomogeneous Medium Green's Functions for Microwave Imaging of Brain Strokes

E. Konakyeri Arıcı, A. Yapar — Sun, 17 Mar 2019 13:12:41 -0400

In this study, an inverse scattering approach is investigated for the detection and imaging of an abnormal structure (a bleeding or a stroke) inside the human brain. The method is mainly based on the solution of an integral equation whose kernel is the Green’s function of the inhomogeneous medium (corresponding to a human head model) which is obtained by a numerical approach based on Method of Moments (MoM). In this context, an inverse scattering problem related to the difference of healthy and unhealthy brain models is formulated and a difference function is obtained which indicates the region where the anomaly is located by solving this inverse problem. In order to reduce the reflection effects caused by the electromagnetic differences between the free space and the brain, a matching medium is used as the background space.

A Low Profile Wideband Log Periodic Microstrip Antenna Design for C-Band Applications

M. Yerlikaya, S. S. Gültekin, D. Uzer — Sun, 17 Mar 2019 12:27:53 -0400

In this study, a wideband low profile microstrip antenna design for C-band applications is presented. The proposed antenna consists of a monopol log periodic patch in the equilateral triangular dimensions with the microstrip line fed and a rectangular ground plane. The antenna has 9×19.8 mm² overall size, thickness of 1.6 mm and 4.3 dielectric constant. According to the simulation results, the proposed antenna has a very wide bandwidth while operating in the frequency band of 4.25-7.95 GHz and 5 GHz resonance frequency. The proposed antenna was also prototyped on FR4 substrate with the 0.02 tangent loss and the measurement results were quite similar by the simulated results.