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Abstract: In this paper a second iteration Sierpinski carpet fractal shape UWB antenna with hexagonal boundary is presented. The antenna covers the frequency band from 3GHz to 12GHz (VSWR≤2). The proposed antenna has the capability to reject 5.15–5.825GHz band assigned for IEEE802.11a and HIPERLAN/2 which is achieved by embedding a ‘Y’ shaped slot in the radiator that extends to the central conductor of the CPW feed as well. A fabricated prototype is developed where the simulation and experimental results are in good agreement. Measured peak antenna gain varies from 1.25dBi to 6dBi within the band. The proposed antenna has a compact size of 33mm×32mm that includes the substrate around the radiating element. Time domain characteristic reveal that the antenna is non-dispersive with a variation of measured group delay within 0.5ns over the entire band. [Copyright &y& Elsevier]

Abstract: This article compares input impedances and radiation characteristics of half wavelength Koch fractal V–electric dipoles having included angles 60°, 90° and 120°. The study considers three structures. In the 1st structure the Koch arms open into the V-region, in 2nd structure they open away from the V-region and in the third structure, one arm opens into and the other away from the V-region. A first iteration, structure 1 of V-Koch electric dipole antenna with included angle of 120° was fabricated and the experimental return loss was in good agreement with simulation. At their first resonances the antennas’ gain and input resistance decrease with decrease in included angles, an observation synonymous to Euclidian electric dipoles. In terms of gain, the first structure is found to give better performance than the other two. For this structure, the pattern distortion at the second resonance was also less compared to the other structures. [Copyright &y& Elsevier]

A low profile modified Koch fractal shaped boundary, ultrawideband (UWB) multiple input multiple output (MIMO) antenna is presented. The radiators are elliptically tapered from the feed line with triangular shaped loading. The boundaries of the triangular shaped loading are embedded with modified Koch fractal shape to provide improved impedance matching. A band suppression characteristic at 5.5 GHz is incorporated by using an electric inductive capacitive resonator at the back of the substrate. Enhanced port isolation of <−20 dB is achieved by using a Maple leaf fractal structure shorted with ground plane. The proposed UWB MIMO antenna has peak realized gain of 4 dBi, and envelope correlation factor is less than 0.01. Measured results closely resemble the simulated results. Moreover, an equivalent circuit model of the proposed structure is extracted and compared with the em simulation result, which are in good agreement. [ABSTRACT FROM AUTHOR]

A low profile and broadband slotted microstrip patch antenna on reactive impedance surface (RIS) is proposed as a circularly polarized (CP) planar antenna. The proposed structure consists of metallic via, complementary Landolt C-shape slot loaded patch antenna and a 7 × 7 array of rectangular RIS. The inductive RIS, having magnetic energy storing ability, is utilized to achieve miniaturization and enhancement of circular polarization bandwidth (CPBW). The 3-dB CPBW is further increased by using metallic via and embedding a complementary Landolt C shape slot in the second quadrant of the patch. A fabricated prototype was developed that has an overall size of 61.5 mm × 57 mm × 4.08 mm (0.984λ 0 × 0.912λ 0 × 0.0652λ 0 at 4.8 GHz). Measured and simulated results are in good agreement. The measured 3-dB-axial ratio (AR) bandwidth of the proposed antenna is 28.9% (4428–5815 MHz). The measured impedance bandwidth is 46.52% (3743–5976 MHz), which covers WLAN, Wi-Max and 5G communications. The antenna radiates left-handed CP wave at boresight direction with realized gain ranging from 5.3 to 6.8 dBic within the 3-dB AR bandwidth. [ABSTRACT FROM AUTHOR]

Abstract A compact ultrawideband multiple input multiple output antenna with dual band notch characteristics is proposed. The design utilizes the property of quasi-self-complementary monopoles to achieve a bandwidth that ranges from 2.2 GHz to 11 GHz. The design has a compact size of 30 mm × 41 mm × 1.59 mm. Two quasi-self complementary half circular monopoles are symmetrically arranged to obtain MIMO antenna. Bandnotch characteristics are obtained by adding parasitic strips of Levy's Fractal shape near the feed line. A Hilbert Fractal shaped slot is etched in the ground plane to enhance the isolation (|S 21 | < −20 dB) throughout the operational bandwidth. The measured and simulated radiation patterns are in good agreement and is found to be stable throughout the ultrawideband. Moreover, the measured peak gain is found to be 4 dBi. [ABSTRACT FROM AUTHOR]

This paper presents design evolution of a single elliptical dielectric resonator antenna to achieve wide measured impedance band-width extending from 8.26 GHz to 12.15 GHz. Design evolved from a right circular cylindrical DRA by varying the dimension along the semi-minor axis and thereby resulting in an elliptical DRA that supports near similar field distribution over the X-band. This similar field variation is achieved by tuning the eccentricity of the elliptical geometry, the feed position as well as height of the DRA. A fabricated prototype is developed and measured results agree well with that obtained from simulation. Apart from wide impedance bandwidth, the observed pattern bandwidth is also similar. [ABSTRACT FROM AUTHOR]

In this paper, asymmetrically positioned stub loaded open loop resonators with pseudo interdigital coupling are used to design compact multiband planar bandpass filters. The first design pertains to a dualband BPF that operates at 3.5 GHz and 5.7 GHz. The parameters like position of stub, which quantifies the asymmetry, and length of stub are further optimised using real coded genetic algorithm to evolve a triband BPF. The evolutionary design procedure is supported with an example of triband BPF having passband at 3.5 GHz, 5.5 GHz and 6.8 GHz, respectively. The transmission line models for both filters are developed as well as fabricated prototypes are realised and tested. There is a good agreement between the measured and simulated results. The measured insertion loss at first and second band centred around 3.5 GHz and 5.7 GHz of the dual band BPF are 1.5 dB and 1.25 dB, respectively. For the triband BPF the values are 1.24 dB, 1.6 dB and 1.8 dB at 3.5, 5.5 and 6.8 GHz, respectively. The dualband design covers the WiMAX and IEEE 802.11a bands where as the triband design also covers the 6.8 GHz RFID frequency. [ABSTRACT FROM AUTHOR]

This paper numerically proposes and experimentally investigates a compact coplanar waveguide fed two element ultra-wideband (UWB), multiple-input–multiple-output (MIMO) antenna array accompanying peak isolation and triple band notch mechanism. The proposed antenna consists of two identical printed monopole elements along with the incorporation of multiple 2nd order Hilbert defects in the ground structure and proposes to incorporate three different mechanisms to reduce the electromagnetic interference of the UWB antenna with existing narrowband systems. The measured impedance bandwidth for the intended antenna ranges from 2.7 GHz to 11.22 GHz. The incorporation of notch mechanisms provides interference suppression at the C-band (3.7–4.2 GHz), WLAN (5.15–5.825 GHz), and X-band communication (7.9–8.4 GHz). The overall size of the intended UWB MIMO antenna is 30.75 mm × 37.80 mm. Moreover, the diversity parameters of the proposed UWB MIMO antenna are numerically calculated and empirically investigated, these calculations and investigations depicts high diversity performance. It is noteworthy to observe that the spacing between the elements is staggeringly reduced to 2 mm. The concurrence among the diverse numerical and experimental outcomes supports the candidature of the suggested layout for portable UWB as well as UWB MIMO systems. [ABSTRACT FROM AUTHOR]

A novel approach of improving the impedance matching at lower frequencies of antipodal Vivaldi antenna by Chebyshev tapering is presented in this work. The conventional antipodal Vivaldi antennas are modified by Chebyshev tapered loading which yields an extremely large impedance bandwidth from 1 GHz to 35 GHz, with percentage bandwidth of 189%. The antenna has an overall dimension of 100 mm × 100 mm. The proposed structure shows peak gain of 6.8 dBi and has fairly stable radiation pattern throughout its operating bandwidth. A fabricated prototype is developed and measured characteristics are in good agreement with simulated results. [ABSTRACT FROM AUTHOR]