Advanced Electromagnetics

Design of Circularly Polarized Modified Minkowski Fractal Based Antenna for UHF RFID Reader Applications

S. Pandey, G. P. Pandey, P. M. Sarum — Sat, 24 Nov 2018 12:04:39 -0500

A compact, square shaped microstrip fractal antenna with asymmetrical pairs of T-slits for circularly polarized (CP) radiation and radio frequency identification (RFID) reader applications is proposed and experimentally investigated. Design is based on narrow slit modified Minkowski island fractal geometry. Circular polarization along with size reduction is achieved by inserting four symmetrical pairs of T-slits at the square patch boundary of the single-probe-feed radiator. Proposed geometry is tuned at resonant frequency of 914 MHz by optimization of dimensions of the two T-slits. Compactness of the antenna is achieved by increasing the overall sizes of the slits. Antenna is fabricated on FR4 substrate with a size of 47.2×47.2×1.6 mm³ (0.143λ₀X 0.143λ₀X 0.005λ₀) and tested to validate the simulated results. The 3-dB axial-ratio (AR) bandwidth and impedance bandwidth of the proposed antenna design are found to be 7 MHz (911-918 MHz) and 24 MHz (909-933 MHz) respectively. A design equation is develped based on the parametric study that can be used to design a compact antenna with CP for UHF RFID applications covering the frequency range from 887 to 1023 MHz.

A Compact ACS-Fed Tri-band Microstrip Monopole Antenna for WLAN/WiMAX Applications

D. Kahina, C. Mouloud, D. Mokrane, M. Faiza, A. Rabia — Sat, 24 Nov 2018 11:32:11 -0500

This paper proposes a novel small asymmetric coplanar strip (ACS) fed tri-band monopole antenna for WLAN and WiMAX applications. To tune and create multiple resonant frequencies, the exciting strip of monopole antenna is connected to two different arms which are a J-shaped directed toward the asymmetric ground plane and an open stub. The proposed monopole antenna with a total size of 14.6 x17.5 mm2 is fabricated and tested. The measured results indicate that the antenna has impedance bandwidths for 10-dB return loss reach about 500 MHz (2.01-2.52 GHz), 230 MHz (3.48-3.71 GHz) and 1.2GHz (5.59-6.72 GHz) which cover widely the 2.4/5.8 GHz WLAN bands and the 3.5GHz WiMAX band. The simulated radiation patterns of the proposed antenna at the three resonant frequencies have a dipole-like radiation pattern in both E-and H-Planes. The compact size, the simple structure and good radiation performances of the proposed antenna makes it well-suited forthe intended applications.

Effect of Substrate Scaling on Microstrip Patch Antenna Performance

A. Esmaeilkhah, C. Ghobadi, J. Nourinia, M. Majidzadeh — Sat, 24 Nov 2018 08:13:53 -0500

The Maxwell field equations (MFEs), as ecumenical model of electromagnetic phenomena, are scale-invariant under Lorentz Transformation (LT). To apply LT, some considerations are required which are not all practically available or technologically attainable; hence, the scale-invariant feature may not be reached effectively. Paving the way to focus on this issue, the effect of substrate thickness scaling as an uncontrollable parameter, is explored on eight identical patch antennas with different substrate thicknesses. In this way, the resonant frequency and complex value of return loss are measured. The effect of manufacturing tolerances of dielectric thickness on resonant frequency deviation and return loss magnitude are carefully studied, too. Also the unwanted distortive effect of selected electrical connection, say as a female SMA connector, is investigated at higher frequencies. The obtained results are comparatively analyzed which confirm the practical bottlenecks in meeting the antenna parameters scaling.

A Multiband Slot Antenna loaded with Stubs for WLAN/WiMAX/Satellite TV Applications

I. Khan, T. Ali, G. D. Devanagavi, S. K R, R. C Biradar — Sat, 24 Nov 2018 07:38:19 -0500

A compact planar multiband antenna operating at 2.65 (lower WiMAX)/5.20 (WLAN)/6.75/7.30 GHz (Satellite TV) is presented. The antenna consists of circular radiator in which a rectangular slot is etched out. Also, the circular radiator is loaded with a rectangular and two hook-shaped stubs to achieve multiband operations. The impedance matching at these bands is achieved by using two small square stubs placed inside the hook-shaped stubs. The antenna has an electrical dimension of 0.17λ_lx 0.17λ_lx 0.01λ_l at the lower frequency of 2.65 GHz. The antenna has S₁₁<-10dB bandwidth of 3% (2.6-2.68GHz), 2.3% (5.12-5.24GHz), 1.2% (6.68-6.76GHz) and 1.37% (7.26-7.36GHz) in simulation and about 6.25% (2.48-2.64GHz), 2.24% (5.3-5.42GHz), 1.15% (6.92-7.00GHz) and 1.1% (8.04-8.12GHz) under measurement. The entire simulation analysis of the antenna is carried out using HFSS v.13.0.

A Triband Planar Inverted-F Antenna with Quadratic Koch Fractal Shaped Slit Along with a Shorted Parasitic Strip

D. Kumar, D. Chowdhury, R. Ghatak — Sat, 24 Nov 2018 00:00:00 -0500

In this paper, a novel compact tri-band planar inverted-F antenna (PIFA) for mobile communication application is proposed. The antenna is capable to cover GSM 900 MHz, DCS 1.8 GHz and WLAN (IEEE 802.11b) 2.45 GHz bands. The proposed PIFA is composed of a quadratic Koch shape slit and a parasitic strip. The PIFA with the fractal shaped slit contributes to the first and second resonance while the shorted strip brings forth the third band. The impedance bandwidths of 84 MHz, 132 MHz and 81 MHz for GSM 900, DCS 1800 and WLAN (IEEE 802.11b) 2450, respectively are achieved. A realized gain of 2.44 dBi, 4.48 dBi and 3.86 dBi is obtained at 0.9 GHz, 1.8 GHz and 2.45 GHz, respectively. The proposed antenna is fabricated and |S₁₁| dB is measured. Reasonable agreement between simulated results as well as measured results is obtained.

Review on Design of Frequency Selective Surfaces based on Substrate Integrated Waveguide Technology

K. K. Varikuntla, R. Singarav — Sat, 24 Nov 2018 00:00:00 -0500

The spectacular development of frequency selective surfaces (FSS) as a spatial filter, absorbers and reflectors made them feasible for the aerospace and defence applications. The intervention of substrate integrated waveguide (SIW) technology into FSS results in the improvement of unit cell structures and better performance by isolating them from inter-element interference. Such FSS structures with SIW cavities upholds the FSS properties and improves their selectivity and performance. Considering the diversity in applications of introducing SIW cavity technology into FSS, the aim of this paper is to furnish a study on the glimpse of EM design techniques to analyze this type of structures. Design topologies of narrowing bandwidth, dual resonance, the design of FSS with sharp sideband edges and frequency selective polarization rotating structures are presented. Further, a novel design for improving the bandwidth of reflective FSS is discussed based on SIW technology. Fabrication techniques pertaining to this type of structures are presented in brief.

A Novel Dual Band Hexagonal Antenna for Bluetooth and Uwb Applications With Single Band Notched

M. Elhabchi, M. N. Srifi, R. Touahni — Sun, 18 Nov 2018 00:00:00 -0500

This paper presents a regular hexagonal antenna for ultra wide bandwidth (UWB). Then this antenna is modified to obtain a dual band with single band notched.The Bluetooth band is integrated in ultrawideband (UWB) when the antenna is loaded by pair of inverted 𝛤-shaped strips.To avoid interference with the uwb systems , the wireless local area network of 5.72–5.825 GHz (IEEE 802.11a) is notched by incorporating a complementary split ring resonator (SRR) slot within the hexagonal shaped . The operating frequency ranges of the proposed antenna are 2.22 GHz - 2.52 GHz and 3.5 GHz - 10 GHz, which covers Bluetooth (2.4 GHz - 2.484 GHz) and UWB (3.1 GHz - 10.6 GHz) band, besides the range of Wlan (5.72 GHz - 5.825 GHz) with return loss more than 10 dB. The performance of the antenna is simulated and optimized by CST Microwave Studio and validated against using Ansoft HFSS . Surface current distributions is used to analyze the effects of the slot and strips. The antenna shows an acceptable gain over both Bluetooth and UWB bands. In the band notched regions, the gain reduces from its normal value to about 4 dBi at 5.75GHz.

Iterative Scattering by Two PEMC Elliptic Cylinders

A.-K. Hamid — Wed, 19 Sep 2018 07:18:24 -0400

Iterative procedure is implemented to derive rigorous solution to the problem of plane electromagnetic wave scattering by couple of perfect electromagnetic conducting (PEMC) elliptic cylinders due co and cross polarized scattered fields among cylinders. The translation addition theorem for Mathieu functions is enforced to compute the higher order scattered fields by single PEMC elliptic cylinder in terms of the other elliptic cylinder coordination system to impose the boundary conditions. The kth co and cross polarized scattered field coefficient expressions are extracted by iteration procedure without using matrix inversion.

Comparative Study of the Accuracy of Analytical Inductance Formulae for Square Planar Spiral Inductors

H. A. Aebischer — Wed, 19 Sep 2018 00:00:00 -0400

In the design of radio frequency (RF) microelectronic integrated circuits (IC’s) and of antennas for short-wave radio frequency identification (RFID) and telemetry systems, planar spiral coils are important components. Many approximate analytical formulae for calculating the inductance of such coils can be found in the literature. They can simplify the problem of designing inductors to a predefined inductance considerably. But the error statistics given by different authors cannot be compared because they are based on different or unknown domains of definition. Hence, it is not possible to decide which formula is best in a given case by merely studying the literature. This paper compares the maximum relative errors of six of some of the most cited formulae in the literature. To all formulae, the same domains of definition are applied. Each of them spans all four dimensions of the parameter space. Precise inductances are obtained numerically with the help of the free scientific and industrial standard software FastHenry2 and used as reference values to calculate the errors of the formulae. It has been found that the alleged maximum errors reported by some authors are far too optimistic. Only two formulae feature small enough errors to be useful in circuit design. The method and the domains of definition applied in the present study may also prove useful for the assessment of future formulae.

A New Approach to the Analysis of Electromagnetic FEM Simulations Results at Electric Field Singularities

G. Betti Beneventi, M. DalRe, L. Vincetti — Wed, 19 Sep 2018 00:00:00 -0400

A new methodology to the analysis of the results of Finite-Element Modeling (FEM) simulations at electric field singularities is proposed. The method, that can be easily applied in the post-processing phase of the electromagnetic FEM analysis workflow, is based on the weighted averaging of the calculated electric field magnitude within small volumes including the singularity point under investigation. In the paper, the proposed approach is applied to the electrical stress analysis of a high-voltage device modeled by means of a commercial electromagnetic FEM tool. In comparison to the conventional metric of the maximum field evaluation usually adopted for the analysis of electrical stress in insulators, our approach features several advantages: (i) the outcome of the analysis is independent of the numerical grid refinement at the singularity, thus allowing direct comparison of calculated electric field with the material dielectric strength; (ii) the method is robust against slight modifications of the geometrical shape of the singularity; (iii) on the other hand, for a given shape, the analysis outcome responds to significant variations of the singularity size or, in other words, of its sharpness; (iv) in the analysis of highvoltage devices, the approach can be applied for the estimation of the discharge volumes corresponding to different singularity types of different device geometries. In the paper, the new methodology is explained in details and is applied to simple but significant case studies.