Advanced Electromagnetics

Scattering from a Buried PEMC Cylinder Illuminated by a Normally Incident Plane Wave Propagating in Free Space

A. Hamid, F. Cooray — Sun, 30 Dec 2018 05:24:57 -0500

A rigorous solution is presented to the problem of scattering by a perfect electromagnetic conducting (PEMC) circular cylinder buried inside a dielectric half-space that is excited by a normally incident transverse magnetic (TM) plane wave propagating in free space. The plane wave incident on the planar interface separating the two media creates fields transmitting into the dielectric half- space becoming the known primary incident fields for the buried cylinder. When the fields scattered by the cylinder, in response to those fields incident on it, are incident at the interface, they generate fields reflected into the dielectric half-space and fields transmitted into free space. These fields, and the fields scattered by the cylinder are expressed in terms of appropriate cylindrical waves consisting of unknown expansion coefficients which are to be determined. Imposing boundary conditions at the surface of the cylinder and at a point on the planar interface, enables the evaluation of the unknown coefficients. This procedure is then replicated, by considering multiple reflections and transmissions at the planar interface, and multiple scattering by the cylinder, till a preset accuracy is obtained for the reflection coefficient at the particular point on the interface. The refection coefficient at this point is then computed for cylinders of different sizes, to show how it varies with the PEMC admittance of the cylinder, its burial depth, and the permittivity of the dielectric half-space.

Design of dual and Wideband Rectangular Patch Antenna for C and X Band Applications

S. Lakrit — Sun, 16 Dec 2018 05:43:46 -0500

In this paper, we resolve two issues of microstrip antennas, which are miniaturization and efficiency behavior. For that, a rectangular patch antenna with 16×18×1.6 mm3 dimensions with dual-band characteristics, was designed, fabricated and characterized. In order to improve the problem of narrow bandwidth in microstrip antennas, we implement in this study the slot technique, allowing us to achieve our purpose. This technique, lead to a good reflection coefficient and VSWR. The characteristics of the fabricated antenna were measured and analyzed by Vector Network Analyzer. The results show two resonance frequencies that define two bandwidths defined by a return loss less than -10 dB and are respectively; 7.47 GHz at a frequency of 400 MHz, and 11.01 GHz at a frequency of 790 MHz. Also, the obtained gain has a good value and it’s very remarkable according to the small size of the structure, with a peak value of 6.1 dB at 12.5 GHz. The small size and good characteristics enlarged the applications domains of our structure, from telecommunications and especially Radar, satellite communications to medical and wireless applications.

Metamaterial Based Circular Disc Patch Antenna Miniaturization

V. Kumar, Y. Wu — Sat, 15 Dec 2018 10:25:20 -0500

A novel metamaterial structure has been proposed for its operation at 2.4 GHz. A circular disc patch antenna resonating at dual band frequency with 2.4 GHz and 3.36 GHz has been designed using full field solver CST MWS tool and the loading effect of the metamaterial has been shown. The loading of metamaterial shows a radial size reduction of 56.71% in the circular disc patch (dimensional space reduction by 81.26%) while the effect of loading the metamaterial array and loading the metamaterial with defected ground plane show that without reducing the disc patch radius, the patch antenna can resonate at 1.00 and 1.942 GHz respectively, these yield a lower frequency shift of 58.33% and 19.79%. The designed metamaterial consists of two copper conductive concentric circular rings over a polyimide substrate. Various antenna parameters such as S11, VSWR, Bandwidth, Gain, Directivity and Radiation efficiency have been obtained for the circular disc patch antenna, circular disc patch antenna loaded with the metamaterial, circular disc patch antenna loaded with an array of metamaterial and are compared. A spice circuit has been derived for the reflection coefficient of the circular disc patch without loading the metamaterial, circular disc patch loaded with metamaterial using Keysight based ADS tool for its inclusion in a traditional electrical circuit solver tool.

Theoretical and Experimental Study of Split Semi Horse Shoe Structure

G. Singh, S. S. Pattnaik — Sat, 15 Dec 2018 06:26:41 -0500

In this paper a new planar metamaterial structure that looks like semi-horse shoe in shape (SSHSS) is designed and simulated. Theoretical analysis of proposed structure done using equivalent circuit theory. Medium effective parameters are extracted using modified NRW approach which proved the metamaterial property of the new unit cell. Radiation pattern, directivity and gain of the new structure were illustrated which gives the possibility of using SSHSS as the antenna. Proposed structure shows multiband characteristics. This antenna shows high directivity (7.92 dBi, 7.86 dBi, 10.11 dBi) and moderate gain (2.55 dBi, 3.90 dBi, 5.07 dBi) at 5.83 GHz, 8.41 GHz, 10.68 GHz respectively. RT duroid is used for fabrication of prototype of the proposed structure. This new structure can be used as metamaterial inspired antenna as well as normal patch antenna. Experimental results shows good agreement with simulated and theoretical results.The proposed structure has been simulated using IE3D electromagnetic simulator.

X-Band GaN High-Power Amplifier Using Hybrid Power Combining Technique for SAR Applications

Sat, 15 Dec 2018 05:52:22 -0500

An X-band high-power amplifier (HPA) based on gallium nitride (GaN) high electron mobility transistors (HEMTs) has been developed for synthetic aperture radar (SAR) applications. A hybrid power combining technique, including microstrip circuits and waveguides, is used to design the HPA. For reducing the size, four 50 W GaN HEMTs cascaded with one 1-to-4 power divider and one 4-to-1 power combiner form a 4-way power combined PCB circuits. For combing the high power and driving an antenna, two PCB circuits are combined by magic-T waveguides. The transmission efficiency of the power combining is approximately 80%. In the 10% duty cycle (pulse width 100 us), the output power of the HPA is over 200 W across the band of 9.5–9.8 GHz. The maximum output power is 230 W at 9.5 GHz, and the power gain is 8.3 dB at 46.1°C.

Compact Broadband Monopole Antenna for C Band Applications

P. Pathak, P. K. Singhal — Sat, 15 Dec 2018 05:19:00 -0500

This paper reports a new design of broadband monopole patch antenna. The proposed antenna possess corner truncated rectangular patch with slits and defected ground structure, these modifications considerably improves the impedance bandwidth to 41.29% over a wideband (5.1–7.59 GHz). The design is appropriate for wireless communication including WLAN IEEE 802.11 g/a (5.15–5.35 GHz and 5.725–5.825 GHz) and C Band (4–8 GHz) applications. An antenna prototype is fabricated using FR-4 with an electrical permittivity of 4.4. Experimental and numerical simulations of antenna’s radiation characteristic are also reported and exhibits good concurrence.

An Insight into Impact of Partial Ground and Dual Trapezoidal Slots on Bandwidth and Gain considerations for a Microstrip Antenna Array for WiMax Application

G. V. Raviteja — Thu, 13 Dec 2018 09:50:54 -0500

In this work, design and analysis of microstrip patch antenna is carried out. A (2 X 1) antenna array is considered, with dimensions (W x L) as 35.11 mm x 27.13 mm. The dielectric substrate is taken to be FR4 epoxy with dielectric constant as 4.3 and loss tangent of 0.02. Dual trapezoidal slots are introduced to improve the gain considerations for the considered antenna array. The simulations are carried out and it is observed that the gain is improved. As a second stage in the work, to improve the bandwidth of operation for the dual trapezoidal antenna array, the concept of partial ground is taken into consideration. The simulations are carried in HFSS. It is found out that the introduction of partial ground improved the bandwidth of the antenna structure considered while preserving the gain to the maximum extent possible. The gain was found to be 7.0875 dB with centre frequency 2.4020 GHz. The frequency range below -10dB for the considered antenna array structure with partial ground was around 2.3 GHz to 2.6 GHz. This range is utilized in the WiMax application which covers the frequency ranges (2.3 GHz to 2.4 GHz) and (2.496 GHz to 2.690 GHz).

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.