Wee Fwen Hoon

Modified cuckoo search algorithm in weighted sum optimization for linear antenna array synthesis

In this study, we proposed a bio-inspired technique known as modified cuckoo search (MCS)-based weighted sum algorithm towards synthesizing symmetric linear array geometry with minimum side lobe level (SLL) and/or nulls control. The newly evolved metaheuristic algorithm was primarily based on the natural obligate brood parasitic behavior of some cuckoo species in combination with the Lévy flight behavior of some birds and fruit flies. Through the integration with the Roulette wheel selection operator and the inertia weight controlling the position (solution) exploration, the MCS-based weighted sum approach optimized concurrently the array element excitation locations, amplitudes, and phases within the uniform pattern and Dolph-Chebyshev window, respectively. The optimal solutions obtained were then compared against the conventional (with λ/2 inter-element distance) and other chosen evolutionary algorithms-based arrays.

Measurement of pyramidal microwave absorbers using RCS methods

In this work, a commonly used measurement techniques were used to define the reflection loss performance of pyramidal microwave absorbers mounted on a wall. The technique is namely, Radar Cross Section (RCS) measurement method. Six set of pyramidal microwave absorbers and flat square absorbers were installed at one side wall, in an RF shielded room in order to investigate the performance. Two types of cable losses measurement techniques were applied to compare its performance under different loss conditions. The reflection loss values resulting from this investigation were then analyzed and discussed.

Frequency selective surface for enhance WLAN applications

This paper proposes the deployment of frequency selective surface (FSS) structure in WLAN device. Objectives to create a band pass square-loop filter FSS in WLAN device to increase the received signal strength of WLAN signal 2.4GHz. FSS works to enhance the 2.4 GHz signal and attenuate the rest signal other than 2.4 GHz. The WLAN signals increasing more than 50 % when pass through the FSS structure.

Tuneable dual-mode narrowband bandstop filter using loaded microstrip resonator

Novel tuneable dual-mode narrowband bandstop filter using loaded microstrip resonator is presented. The filter is designed by using coupled line coupling with the microstrip resonator. There is two different pair of loaded resonator that produces a dual band bandstop filter. The dual band bandstop resonance frequency can be tuned independently by adjusting the resonator width and length. To achieve high selectivity of the bandstop filter response, defected ground structure (DGS) is applied in the filter layout. The tapped lines structure (TLS) are used to suppress second harmonic frequency. The dual band bandstop filter is resonant at 2.4 GHz with 200 MHz of bandwidth and 5.8 GHz with 300 MHz of bandwidth. The bandstop filter layout is fabricated on RO 4003C with 0.508 mm of substrate thickness. It is compact dimension with 19.6mm × 38.8mm. The advantages of this bandstop filter are simple layout and it can be tuned to the specified frequencies.

Determination of Dielectric Properties of Bismuth Titanate (BiT) Ceramic Material for WiMAX/WLAN Antenna

The utilization of Bismuth Titanate (BiT) as a ceramic material on an antenna has been investigated. The BiT ceramic material is of interest for a range of Wireless Local Area Network (WLAN) IEEE 802.11 b/g and Worldwide Interoperability for Microwave Access (WiMAX) IEEE 802.16 application, which covers the range of 2.3 GHz to 2.5 GHz. The BiT ceramic material had been tested to own a high dielectric constant of εr= 15 that is able to miniaturize an antenna. There is a high demand nowadays on the miniature antenna for smaller devices. An experimental prototype at WiMAX/WLAN range was built and measured on its dielectric properties, especially the dielectric constant and dielectric loss of the prototype material.

Switchable beam antenna

This paper introduces the Switchable Beam antenna which has the ability to shift the direction of the Wi-Fi signal to any specific direction depending on the availability of user. The designs of eight radiating patches are installed in between aluminum plates which are fixed by the edges of the other aluminum plate. This is to represent eight angles where the antenna will radiate. By using switches, the beam of the radiating energy can be adjusted to be directed to a specific area. This antenna is operational at 5.8 GHz which is Wi-Fi frequency. The antenna generated a gain of 4.07 dB while the directivity is 9.986 dBi. Apart from Wi-Fi applications, the design can be customized in different frequency to support different application such as GSM.

The Design of Ultra-High Frequency (UHF) Radio Frequency Identification (RFID) Reader Antenna

This paper presents the design of ultra-high frequency (UHF) radio frequency identification (RFID) reader antenna using low dielectric constant of microwave substrate. An RFID reader antenna emits electromagnetic signals to the microchip in the tag, and the microchip will be energized by modulating the wave and returns to the reader antenna. The process of wave emitting is known as backscattering due to the presence of tag been detected by the reader. High-dielectric constant substrate, for example flame-retardant-4 (FR4) which is commonly used for microstrip patch antenna, is high in dielectric constant and dielectric loss. Thus, this will lead to low gain and directivity properties of the antenna. To overcome this matter, low-dielectric constant substrate which is Taconic TLY-5 was proposed to be utilized for microstrip patch antenna design. The TLY-5 microstrip substrate thickness used is 1.6 mm, dielectric constant of 2.2, and loss tangent of 0.019. A high-conductivity metal which is typically a conductive copper is been used for the two layers of dielectric substrate, the top radiating patch layer and bottom ground layer where the copper thickness is 0.035 mm. Microstrip feed line is used for this UHF RFID reader antenna. The width of the feed line was tuned to obtain impedance matching of 50 Ω. The proposed antenna which is fork-shaped patch antenna was simulated using Computer Simulation Technology (CST) and Microwave Studio software at resonant frequency of 910 MHz with the outcome results of 7.985 dB gain and −11.11 dB return loss. Nevertheless, the typical value obtained for VSWR is less than 2.

Side lobe suppression of Vivaldi antenna using shorting pin structure

This paper was executed in order to design side lobe suppression of Vivaldi antenna using shorting pin structure at S-band frequency. Nowadays, Vivaldi antenna has been used to satellite communications, remote sensing and radio telescope. There are a variety of designs such as tapered slot Vivaldi antenna, antipodal Vivaldi antenna and balanced antipodal Vivaldi antenna. Tapered slot Vivaldi antenna has been selected to design the project. The design of the antenna is start with patch antenna by using basis of transmission line model (TLM) formula to calculate the length and width of the patch. It is shaped into Vivaldi antenna. For the final design, the shorting pin structure will connect the patch on top side and the ground plane to absorb the unbalanced current. The shorting pin will reduce the side lobe. The antenna was simulated by using CST Microwave Studio. Based on the simulation results, the Vivaldi antenna shows a good performance as the return loss less than - 10 dB, voltage standing wave ratio, gain, directivity and radiation pattern was obtained the desired result as for a resonant frequency of 3 GHz. The radiation pattern of Vivaldi antenna with shorting pin structure reducing as compared with the design without shorting pin structure. The final antenna design shows that it has a few main lobe magnitudes where the antenna can focus and direct the energy for transmission or receiving of the energy signal.

Full ground plane dual-band microstrip antenna for ISM and HiperLAN/2 applications

A full ground plane dual band microstrip antenna (FGP-DBMA) over ISM and HiperLAN/2 applications is presented. The structural design of the FGP-DBMA is based on suspended plate antenna. The FGP-DBMA antenna features a 56 × 55 mm2 rectangular radiating element suspended over 90 × 90 mm2 ground plane. ShieldIt Super conductive textile features are used as the radiating element and ground plane while felt textile features are used as the dielectric substrate. The rectangular radiator patch is designed using slits for dual-band resonance over ISM band (2.4 GHz to 2.48 GHz) and HiperLAN/2 band (5.725 GHz to 5.875 GHz). The FGP-DBMA radiates unidirectional with a fully grounded plane to avoid coupling onto users body. The FGP-DBMA shows efficiency over the range of 69.6 % to 75.6 % and gain over the range of 6.052 dB to 6.323 dB in the free space scenario. The evaluation of FGP-DBMA with bending effects shows no significant changes to the performance of the FGP-DBMA. This indicates that the curvature effect on the proposed FGP-DBMA for on-body performance, i.e. on human arm, does not affect the performance of the antenna.

On the Miniaturization High Permittivity DRA with Array Patches

The miniaturization on planar printed-circuit antennas by loading the ceramic material of high permittivity material bismuth titanate has been experimentally demonstrate on the micro strip patch antenna. Due to its very small size and radiation performance, it is compatible for packaging constraints and can be easily integrated in a big variety of portable devices. The results show that the size reduction is achieved with the gain of the ceramic material antenna comparable with that of conventional micro strip antenna. In this paper, the miniaturized antenna array technology with high permittivity ceramic material, bismuth titanate array antenna is described, along with comparison computer simulation results with conventional micro strip patch antenna.