A coaxial probe-fed sector shaped patch antenna with the three corners truncated generates a triple band resonance by employing the higher order modes of the patch. A fourth sectoral indentation is ...used to tune the third band. The antenna is fabricated on an FR4 substrate of size 40 mm × 50 mm × 1.6 mm and experimentally investigated. The resonances cover the UMTS (1.92-2.17 GHz), WiMAX (3.3-3.6 GHz), and the ISM 5.2 (5.1-5.3 GHz) bands with 10 dB return loss bandwidths of 11.2%, 5.14%, and 3.9%, respectively, and 3-dB axial ratio bandwidth of 5.8% in the first band. The polarization is circular in the UMTS band and linearly orthogonal in the other two bands. The frequency ratio of the two linearly polarized bands is tunable in the range 1.39-1.51. Area reductions of 6.6% in the patch and 64% in the ground plane with respect to the work on disc sector patch antenna by Hsu et al. are obtained.
A novel compact microstrip fed dual-band coplanar antenna for wireless local area network is presented. The antenna comprises of a rectangular center strip and two lateral strips printed on a ...dielectric substrate and excited using a 50 Omega microstrip transmission line. The antenna generates two separate resonant modes to cover 2.4/5.2/5.8 GHz WLAN bands. Lower resonant mode of the antenna has an impedance bandwidth (2:1 VSWR) of 330 MHz (2190-2520 MHz), which easily covers the required bandwidth of the 2.4 GHz WLAN, and the upper resonant mode has a bandwidth of 1.23 GHz (4849-6070 MHz), covering 5.2/5.8 GHz WLAN bands. The proposed antenna occupy an area of 217 mm 2 when printed on FR4 substrate (epsiv r =4.7). A rigorous experimental study has been conducted to confirm the characteristics of the antenna. Design equations for the proposed antenna are also developed
In this paper, the anomalous dispersion behavior of polyaniline–carbon nanotube (PANI–CNT) composites for various microwave bands is presented. The anomalous dispersion behavior is experimentally ...verified by observing group delay characteristics using vector network analyzer. In an anomalous dispersive medium, the transmission coefficient is characterized by an advancement in phase, while for a normal medium, the transmission phase shows a gradual decrease. By closely observing this property, we can correlate different material property deviations associated with the anomalous dispersion region of the sample in various microwave bands. The samples of PANI–CNT, in their powder forms, are used for the study. PANI–CNT is normally exhibiting diverse material properties compared with the normal EMI shielding materials which are inevitable for shielding applications. In this paper, the effect of anomalous behavior on various material parameters like permittivity and shielding efficiency (SE) is studied. The advantage of anomalous dispersion is that the region is characterized by a significant enhancement of SE as compared to the existing EMI shielding materials used for microwave applications.
An electronically reconfigurable microstrip antenna with circular and linear polarization switching is presented. The prototype fabricated on a substrate of dielectric constant (ε r ) 4.4 and height ...(h) 1.6 mm is fed by a proximity feed fabricated using the same substrate. By controlling the bias voltage of two PIN diodes, the polarization of the antenna can be switched between three states; two states for linear polarization (horizontal and vertical) and one state for circular polarization (RHCP). Simulation and experimental results show that the proposed antenna has a cross polar level better than 10 dB in the linear polarization state and 18 MHz axial ratio bandwidth in the circular polarization state. The frequency and polarization diversities of this design could potentially improve the reliability of wireless communication systems.
Electromagnetic safeguards are key factors for electronic devices. Lightweight and highly flexible polymer composite films with high electrical conductivity are considered to be efficient ...electromagnetic interference (EMI) shielding materials. Polymer composites offer alternative to metal-based composites which have poor flexibility, corrodibility, and are difficult to process. Here, highly flexible polyvinyl alcohol
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poly (3, 4-ethylenedioxythiophene):polystyrene sulfonate/multiwalled carbon nanotube (PVA/PEDOT:PSS/MWCNT) free-standing composite films were fabricated by a solution mixing process followed by a simple solvent casting technique. PVA/PEDOT:PSS/MWCNT composite films of thickness around 20 microns showed high EMI shielding effectiveness (SE) in the X-band over the frequency range of 8–12 GHz. Incorporation of MWCNT into the polymer matrix considerably increased the mechanical strength of the PVA/PEDOT:PSS/MWCNT composite free-standing film. This investigation revealed that PVA/PEDOT:PSS/MWCNT composite film with 0.5 wt.% of MWCNT showed excellent absorption-dominated EMI SE of 60 dB over the frequency range of 8–12 GHz with extensive tensile strength. Our study opens a facile way to design flexible, lightweight and free-standing films as EMI shielding for next-generation flexible electronic devices.
A compact, wideband, printed slot antenna, suitable for wireless local area network (WLAN) and satisfying the worldwide interoperability for microwave access (WiMAX) applications, is proposed. The ...antenna microstrip-fed and its structure is based on Koch fractal geometry, where the resonance frequency of a conventional triangular slot antenna is lowered by applying Koch iterations. The antenna size inclusive of the ground plane is compact and has a wide operating bandwidth. The proposed second iteration Koch slot antenna operates from 2.33 GHz to 6.19 GHz covering the 2.4 GHz/5.2 GHz/5.8 GHz WLAN bands and 2.5 GHz/3.5 GHz/5.5 GHz WiMAX bands. The antenna exhibits omnidirectional radiation coverage with a gain better than 2.0 dBi in the entire operating band. Design equations for the proposed antenna are developed, and their validity is confirmed on different substrates and for different slot sizes.
The physical existence of microwave toroidal dipole in a dogbone metallic inclusion-based miniaturized cloaking structure is verified in this paper. The excitation of toroidal dipole moments on the ...studied composite is verified using multipole scattering formalism. The presence of the toroidal Fano resonance significantly enhances resonant forward scattering from the structure for normal incidence. Multipolar contribution from the electric, magnetic and toroidal moments significantly enhances the scattering cross-section of the composite as compared to a bare cylindrical metallic object. Applicability of the proposed scheme is tested inside an anechoic chamber using reflection measurements on the fabricated structure and is subsequently validated in computer simulations in the microwave frequency regime.
A broadband printed microstrip antenna having cross polarization level >; 15 dB with improved gain in the entire frequency band is presented. Principle of stacking is implemented on a strip loaded ...slotted broadband patch antenna for enhancing the gain without affecting the broadband impedance matching characteristics and offsetting the position of the upper patch excites a lower resonance which enhances the bandwidth further. The antenna has a dimension of 42 × 55 × 4.8 mm 3 when printed on a substrate of dielectric constant 4.2 and has a 2:1 VSWR bandwidth of 34.9%. The antenna exhibits a peak gain of 8.07 dBi and a good front to back ratio better than 12 dB is observed throughout the entire operating band. Simulated and experimental reflection characteristics of the antenna with and without stacking along with offset variation studies, radiation patterns and gain of the final antenna are presented.
The quest for invisibility has inspired a deep ardour in the research community over the past decade. The invention of metamaterials has boosted the research on electromagnetic cloaking due to its ...unusual electromagnetic parameters under plane wave incidence. In this study, we propose a novel cloaking scheme, using dogbone metamaterials, for effectively routing the incident electromagnetic fields around a target metal cylinder under consideration. Notable reduction in the scattered power is observed from the target in comparison to an uncloaked target. Experiments and simulations validate an effective reduction in the scattering cross section of the target and effective guiding of the incident plane wave around the target.
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