Sharul Kamal Abdul Rahim

Two-Segments Compact Dielectric Resonator Antenna for UWB Application

A new compact two-segments dielectric resonator antenna (TSDR) for ultrawideband (UWB) application is presented and studied. The design consists of a thin monopole printed antenna loaded with two dielectric resonators with different dielectric constant. By applying a combination of U-shaped feedline and modified TSDR, proper radiation characteristics are achieved. The proposed antenna provides an ultrawide impedance bandwidth, high radiation efficiency, and compact antenna with an overall size of 18 × 36 × 11 mm . From the measurement results, it is found that the realized dielectric resonator antenna with good radiation characteristics provides an ultrawide bandwidth of about 110%, covering a range from 3.14 to 10.9 GHz, which covers UWB application.

Novel Design of Compact UWB Dielectric Resonator Antenna With Dual-Band-Rejection Characteristics for WiMAX/WLAN Bands

A novel compact dual band-notched dielectric resonator antenna (DRA) for ultrawideband (UWB) applications is proposed. Here, the bandwidth enhancement and the first band notch is realized by embedding a stub that is located to the hollow center of a U-shaped feedline simultaneously. By etching an inverted T-shaped parasitic strip at the back plane of an antenna that is surrounded by a dielectric resonator (DR), the second band rejection is created. By cutting a slot at the proper position on the ground plane, the width of the second band notch is controlled. The proposed antenna size is 12 ×30 ×6 mm3 or about 0.124 λ×0.31 λ×0.062 λ at 3.1 GHz. The measurement results demonstrate that the proposed DRA provides acceptable radiation performances such as an ultra-wide impedance bandwidth of around 122% with two sufficient band rejections in the frequency bands of 3.22-4.06 and 4.84-5.96 GHz, high radiation efficiency, and nearly constant gain.

A new rain attenuation conversion technique for tropical regions

Rain attenuation is one of the most crucial factors to be considered in the link budget estimation for microwave satellite communication systems, operating at frequencies above 10GHz. This paper presents a mathematical model for converting terrestrial rain attenuation data to be used for satellite applications at Ku-band. In the proposed technique, the ITU-R P 618-9, together with a combination of ITU-R P 530-12 and the revised Moupfouma model have been adopted for satellite and terrestrial rain attenuation predictions, respectively. The model has been used for transforming the measured rain attenuation data of some DIGI MINI-LINKS operating at 15GHz in Malaysia, to be used for MEASAT 2 applications. It was found that the model predictions are fairly reasonable when compared with direct beacon measurements in Malaysia and similar tropical locations. The model will provide a relatively accurate method for transforming the measured terrestrial rain attenuation to be used for satellite applications; and therefore substantially reduce the cost of implementing Earth-satellite links in some tropical regions that have su-cient rain attenuation data for the terrestrial links.

Ultrawideband Dielectric Resonator Antenna With WLAN Band Rejection at 5.8 GHz

A novel compact ultrawideband (UWB) dielectric resonator antenna (DRA) with a band rejection at 5.8 GHz is proposed and studied. The antenna is composed of a thin monopole printed antenna loaded with DR that is housed into a dielectric substrate and an L-shaped parasitic strip connected to the ground plane. The L-shaped strip and metallic sheet are utilized to improve impedance bandwidth. A modified metallic sheet underneath the dielectric resonator has been applied to create a band rejection at frequency 5.8 GHz. The measurement results exhibit acceptable performances in terms of reflection coefficient, radiation pattern, efficiency, and realized gain.

PSOGSA-Explore

Graphical abstractDisplay Omitted HighlightsWe propose a new algorithm to lower the sidelobes in collaborative beamforming.We achieved up to 100% improvement in sidelobe reduction.Variable parameter tuning is simplified in the proposed algorithm.The proposed algorithm successfully avoids the problem of premature convergence.The proposed method does not increase the computational complexity of the system. A conventional collaborative beamforming (CB) system suffers from high sidelobes due to the random positioning of the nodes. This paper introduces a hybrid metaheuristic optimization algorithm called the Particle Swarm Optimization and Gravitational Search Algorithm-Explore (PSOGSA-E) to suppress the peak sidelobe level (PSL) in CB, by the means of finding the best weight for each node. The proposed algorithm combines the local search ability of the gravitational search algorithm (GSA) with the social thinking skills of the legacy particle swarm optimization (PSO) and allows exploration to avoid premature convergence. The proposed algorithm also simplifies the cost of variable parameter tuning compared to the legacy optimization algorithms. Simulations show that the proposed PSOGSA-E outperforms the conventional, the legacy PSO, GSA and PSOGSA optimized collaborative beamformer by obtaining better results faster, producing up to 100% improvement in PSL reduction when the disk size is small.

A Dual-Band Diamond-Shaped Antenna for RFID Application

A novel dual-band single-layer substrate and diamond-shaped antenna is presented. The proposed antenna operates in dual-band frequency at UHF band (from 902 to 920 MHz) and ISM band (from 2.4 to 2.5 GHz), which is suitable for RFID application. Antenna frequencies were controlled by the shape and size of the radiating element. The proposed prototype antenna also has acceptable performances in terms of gain, efficiency, and directional radiation pattern. The antennas gain and efficiency are 7.8 dBi and 87 %, respectively, at the lower frequency band, while the corresponding values are 9.4 dBi and 94 % at the higher band. When compared to the simulated results, the measurements show good agreement in terms of return loss and radiation pattern.

Frequency-Reconfigurable Rectangular Dielectric Resonator Antenna

A coplanar waveguide (CPW) reconfigurable dielectric resonator antenna (DRA) is presented and investigated. The DRA is capable of frequency tuning at three different frequency bands between 3.45 and 6.77 GHz. The overall size of the antenna is 50 × 57 mm2. The dielectric material is a rectangular block of ceramic with a permittivity of 15. Two switches, implemented using p-i-n diodes, are located on the lines of a feed network that is connected to the dielectric element. Single-band modes with impedance bandwidths of 8% and 16% are achieved by switching “on” one of three connecting feedline networks, whereas a wide band, with an impedance bandwidth of 65%, is achieved by switching “on” two connecting lines. Frequencies in the single band can be independently controlled using switch positions without affecting the wideband mode. The prototype has a low profile with a dielectric resonator thickness of 4 mm. The characteristics of this antenna were studied, and good agreement was found between the numerical and measured results.

CPW-Fed Transparent Antenna for Extended Ultrawideband Applications

A novel coplanar waveguide-fed transparent antenna for ultrawideband applications with enhanced bandwidth is presented. In this design, different techniques have been used to broaden the bandwidth. The rectangular radiator of the antenna is equipped by the staircase technique to increase the overlapped resonant frequencies. Moreover, two major and minor symmetrical rectangular stubs are mounted on top of the quarter-circle slot ground by using a dual axis to significantly increase the bandwidth between 3.15 and 32 GHz for VSWR <; 2. AghT-8 transparent thin film is used in the design of the proposed antenna to obtain a very compact size and lightweight structure.

A Compact Frequency-Reconfigurable Dielectric Resonator Antenna for LTE/WWAN and WLAN Applications

A compact frequency-reconfigurable dielectric resonator antenna (DRA) for LTE/WWAN and WLAN applications is investigated and presented. The proposed antenna provides the frequency tuning between 1.60 and 2.71 GHz. The design consists of four identical rectangular dielectric resonators with permittivity of 10 each and three p-i-n diode switches that are located on the feedline network between each of two dielectric resonators. The proposed antenna size is 20 ×36 ×5.57 mm3, which is suitable for mobile devices. The measurement and simulation results are applied to demonstrate the performance of the proposed antenna. From the measured results, it is found that the proposed antenna with acceptable performance provides four single-band modes with the impedance bandwidths of 17%, 11%, 14%, and 6%.

X-Polarization array antenna with parallel feeding for WiMAX 3.55 GHz application

An X-Polarization array microstrip patch antenna for WiMAX application is introduced in this paper. The array antenna operates at WiMAX frequency of 3.55 GHz. The substrate used is FR-4 with the thickness of 1.6 mm, relative permittivity of 4.5 and loss tangent of 0.019. The antenna use parallel feeding network to feed all the eight elements with coaxial port. The array has gain of 6 dBi, and directivity 8.754 dBi. The array antenna only requires single input port unlike conventional X-Polarization array antenna that uses multiple input port application. Parametric study of cross angle to antenna performance is studied which have not been discussed in the past research and coupling between the elements in the array is presented.