Zainal Arrifin Ahmad

A Novel 5.8 GHz High Gain Array Dielectric Resonator Antenna

In this paper, a novel nine elements array dielectric resonator antenna (DRA) is presented. The DRA was excited by a microstrip feeder with a rectangular aperture coupled slots. The slot positions were determined based on the characteristic of standing wave ratio over a short ended microstrip. The measured gain of the array DRA operating at 5.84 GHz was about 10 dBi having impedance bandwidth of 60MHz. The proposed DRA exhibits an enhancement of the gain in comparison with a single pellet DRA. The size of the whole antenna structure is about 60 mm× 40mm and potentially can be used in wireless systems.

Simulation and Experimental Investigators on Rectangular, Circular and Cylindrical Dielectric Resonator Antenna

In this paper, theoretical and simulation studies on rectangular and annular dielectric resonator antenna (DRA) made of TiO2 was reported. The ceramic was fabricated by solid state reaction at 1200◦C. The structural and dielectric properties were investigated by X-Ray Diffraction (XRD), Field Emission Electron Microscopy (FESEM) and network Analyzer. The XRD results showed the presence of rutile phase and the microstructure comprised of fine grain (0.2–0.5 μm) and large grain 1.0–1.5 μm. The rectangular and annular shape TiO2 DRA with high dielectric constant (e = 84) and low loss tangent (0.080) were fed with 50Ω microstrip transmission line and comparision between the various shape were investigated. The return loss, input impedance and radiation pattern TiO2 DRA was studied. Design simulation results using CST Microwave Studio 2008 also was presented.

NOVEL MODELING AND DESIGN OF CIRCULARLY POLARIZED DIELECTRIC RESONATOR ANTENNA ARRAY

This paper presents a design of circularly polarized dielectric resonator antenna (DRA) array. The dielectric resonators (DRs) were excited by rectangular aperture coupling slots feed with a linear microstrip. The slot positions were determined based on the characteristic of standing wave ratio over a short ended microstrip to deliver the maximum amount of coupling power to the DRs, in order to improve the array gain Each DR element was rotated 45 - with respect to the sides of the exciting slot to generate circular polarization pattern. The DRA array was modeled and simulated as a parallel RLC input impedance component using Agilent (ADS) software, since that will ensure the resonant frequency of the antenna as primary design step before simulating in (CST) software and doing the measurements. The results of the return loss, gain radiation and pattern axial ratio are shown. The gain of the proposed array in X band was about 8.5dBi, while the 3dB axial ratio bandwidth started from 8.14 to 8.24GHz. The impedance bandwidths started from 8.14GHz to 8.26GHz. The proposed DRA exhibited an enhancement of the gain in comparison to a single pellet DRA. The size of the whole antenna structure is about 40mm £ 50mm and can potentially be used in wireless systems.

Aperture and Mutual Coupled Cylindrical Dielectric Resonator Antenna Array

A 1 £ 3 element linear array using cylindrical dielectric resonator antennas (CDRAs) is designed and presented for 802.11a WLAN system applications. The top and bottom elements of CDRA array are excited through the rectangular coupling slots etched on the ground plane, while the slots themselves are excited through the microstrip transmission line. The third element (i.e., central CDRA) is excited through the mutual coupling of two radiating elements by its sides. This mechanism enhances the bandwidth (96.1%) and gain (14.3%) as compared to aperture coupled technique. It is also observed that the side lobe levels are reduced over the designed frequency band. Using CST microwave studio, directivity of 10.5dBi has been achieved for operating frequency of 5.6GHz. Designed antenna array is fabricated and tested. Simulated and measured results are in good agreement. The equivalent lumped element circuit is also designed and presented using Advanced design system (ADS) for this proposed array.

Equivalent Lumped-Element Circuit of Aperture and Mutually Coupled Cylindrical Dielectric Resonator Antenna Array

This paper presents an electrical model of aperture and mutually coupled three-elements cylindrical dielectric resonator antenna (CDRA) array designed for 802.11a system applications. In electrical model, each antenna component is represented by its equivalent RLC circuit. The advanced design system (ADS) software is used to build the electrical model and predict the behavior of return loss, while the antenna structure is simulated using CST microwave studio before fabrication. The flrst and last radiating elements of the proposed array are excited through the aperture slots while the middle element is excited through the mutual coupling of its neighboring elements. The slot length and inter-slot distance efiects on bandwidth are comprehensively analyzed and presented. The maximum gain of the proposed array for 5.0GHz band is about 10.8dBi, and the achieved simulated (CST, ADS) and measured impedance bandwidths are 1.076GHz, 1.0GHz, and 1.2GHz respectively. The proposed CDRA array antenna exhibits an enhancement of the gain (7.4%) and bandwidth (93.3%) as compared to a literature work with aperture slots. In this study, it is also observed that by using the mutual coupling instead of third slot to excite the middle CDRA, side lobe levels are also reduced signiflcantly over the entire 5.0GHz band.

Experimental study on a directional cylindrical dielectric resonator antenna (CDRA) at 5.8 GHz

In this paper an experimental study on a directional cylindrical dielectric resonator antenna (CDRA) at 5.8 GHz is discussed and presented. Dielectric resonator (DR) ceramic-base material is investigated in the design and it is found that it improves the antenna performance. The dielectric constant of dielectric resonator palette is 55 and it is fed with a 50 Ω microstrip transmission line. The aperture coupling technique is highlighted in order to improve the performance of the CDRA in terms of their tuning frequencies, impedance bandwidth, radiation pattern and gain. The CDRA measured results are compared with the simulation, by using the 3D microwave simulator, Computer Simulation Technology (CST).

La‐Doped CaCu3Ti4O12 Prepared By Conventional And Microwave Processing

Two processing techniques were used to prepare separate samples of undoped and La‐doped CaCu3Ti4O12: the conventional furnace and microwave processing. Stoichiometric composition of undoped CaCu3Ti4O12 was produced by mixing starting materials of Ca(OH)2, CuO and TiO2 powder. The mixed powder was milled and then calcined, compacted and sintered using either a furnace (conventional) or a domestic microwave oven (microwave processing). The La2O3 was added to undoped CaCu3Ti4O12 in order to prepare the La‐doped CaCu3Ti4O12 with different doping concentrations. The conventional furnace heating technique requires a calcination temperature of 900° C for 12 hours before the mixture is sintered at 1000° C for 12 hours. However, a single phase CaCu3Ti4O12 compound was successfully synthesized using a microwave oven for a calcination time of 30 minutes. Longer microwave sintering time tends to produce denser CaCu3Ti4O12 pellets.