Noor Asniza Murad

Frequency-Reconfigurable Microstrip Patch-Slot Antenna

A frequency-reconfigurable microstrip patch switchable to slot antenna is proposed. The antenna is capable of frequency switching at nine different frequency bands between 1.98 and 3.59 GHz. The patch is resonating at 3.59 GHz, while the slot produces eight different operating frequencies between 1.98 and 3.41 GHz. Five RF p-i-n diode switches are positioned in the slot to achieve frequency reconfigurability. Simulated and measured results are used to demonstrate the performance of the antenna. The simulated and measured return losses, together with the radiation patterns, are presented.

FRACTAL KOCH MULTIBAND TEXTILE ANTENNA PERFORMANCE WITH BENDING, WET CONDITIONS AND ON THE HUMAN BODY

A multiband Fractal Koch dipole textile antenna is proposed for wearable applications. The antenna is designed to operate at 0.9GHz, 2.45GHz and 5.8GHz. Denim materials as the substrate are selected aiming to obtain robustness, ∞exibility and a lightweight textile antenna. The antenna model is designed, simulated, optimized and analyzed using Microwave Studio CST software. Two types of multiband antenna prototypes are fabricated and evaluated with difierent conducting elements (Shield It fabric and copper foil tape). Antenna performance is observed in terms of return loss, bandwidth, radiation pattern and realized gain. Three difierent comprehensive analyses are taken into consideration: measurement antenna with difierent bending sizes, on-body measurement and under wet conditions. The antenna performances are evaluated based on resonant frequency (fo) and bandwidth (BW). The antennas performance with bending on the human body (arm & forearm) is compared and investigated. A suitable placement on the body has been discovered between the chest and backside. The antennas have also been tested under wet conditions to ensure a stable characteristic under the in∞uence of water.

Hilbert Curve Fractal Antenna for RFID Application

The implementation of radio frequency identification (RFID) involved two main components; the transponder and the reader. The transponder or simply known as a tag comprises of a programmable chip and an antenna. The antenna of the tag has to be of compact size. This paper presents a compact antenna based on the Hilbert curve fractal. The basic antenna is designed at 2.4 GHz, one of the frequencies used in RFID applications. The antenna geometry went through three iterations of fractal process. The designed antennas were then simulated using electromagnetic simulation software. It was observed that a compact Hilbert curve fractal antenna performs well at the desired frequency of operation

Microstrip U-shaped dual-band antenna

This paper presents the design of a dual-operation antenna having microstrip configuration. The chosen dual-operation frequencies are that of indoor mobile system; 0.9 GHz and 2.4 GHz. The design starts with a microstrip square patch antenna being fed by a coaxial probe from underneath the substrate. An FR4 material was used for the design. The antenna was first cut into U-shaped configuration to operate at lower frequency of 0.9 GHz. A smaller square patch was then separately designed to operate at the lower frequency of 2.4 GHz. The feeding is similar, i.e coaxial probe feed. Successive simulations were performed on both antennas. Upon achieving a good impedance match at the input of the U-shaped antenna, the antenna was then integrated with the separately designed smaller square patch element. The smaller patch was coupled to internal region of the U-shaped configuration. The integrated U-shaped antenna was then optimized through successive cycles of simulations in order to operate well at the two frequencies of operations.

Triple band circular ring-shaped metamaterial absorber for x-band applications

This paper presents the design, fabrication, and measurement of triple band metamaterial absorber at 8GHz, 10GHz and 12GHz which are in the X-band frequency range. The unit cell of the metamaterial consists of three concentric copper rings at difierent radii, printed on 0.8mm thick FR4 substrate in order to obtain triple resonant frequencies. The highly symmetrical ring structure in nature makes this absorber insensitive to any polarization state of incident electromagnetic (EM) waves for normal incident waves. The proposed structure is capable to operate at wide variations angle of incident wave. The simulated result shows that the triple-band metamaterial absorber achieves high absorbance for normal incident electromagnetic waves of 97.33%, 91.84% and 90.08% at 8GHz, 10GHz and 12GHz, respectively, when subjected to normal incident electromagnetic. With metamaterial absorber maintaining 50% of absorbance value, the corresponding full width half maximum (FWHM) are 5.61%, 2.90% and 2.33%. The operating angles in which the metamaterial structure can maintain 50% absorbance at TE mode and TM mode are 67 - and 64 - , respectively. The experimental result verifles that the absorber is well performed at three difierent resonant frequencies with absorbance greater than 80%.

Modified bifin fractal antenna with size reduction

This paper discusses the resonance of a modified bifin fractal antenna in comparison to the corresponding printed modified bifin having a centre-feed microstrip line. The antennas are designed based on a finite biconical antenna operating at 1.575 GHz. The Global Positioning Satellite system receiver operates at this frequency. Modifications have been made to the bifin structure which is half-wavelength long. The modification done on the bifin is intended to maintain the operating frequency. Hence, a compact structure can be obtained. By employing a configuration that resembles the fractal, the modified antenna is further reduced in size. The modified bifin antennas have 60/spl deg/ arm flare angle. The antennas have been successfully investigated using numerical simulations. The one-port performance of each modified fractal bifin is investigated and analysed. The structures operate at the corresponding frequency of operations.

Fractal patch antenna for GPS application

Fractal patch antenna is proposed to reduce the size with miniaturization technique, not only for the single element structure, but also in an array design. This paper presents the design of fractal patch antenna based on the basic structure of square antenna operate at 1.575 GHz for global positioning system (GPS) application. The fractal design is introduced into the basic structure intended to reduce the frequency of operation. Hence, miniaturization can be achieved. Simulation has been performed on several sets of the design structures using ensemble SV software. The frequency imposed by the fractal structure is lower than the basic structure.

A Compact Slotted Microstrip Patch Antenna for RFID applications

This paper presents a compact slotted microstrip patch antenna for RFID applications. The antenna is designed to operate at 2.40-2.45 GHz using the Computer Simulation Technology (CST) software. The proposed antenna is designed and fabricated using Flame Retardant 4, FR4 substrate with the design specification dielectric constant (εr) of 4.5 and thicknesses (d) of 1.6mm. In order to minimize the size of the microstrip patch antenna, the proposed antenna contains additional slotted structure attached in the reflector of FR-4 substrate. The new Compact Slotted Microstrip Patch Antenna (CSMPA) reduce by 50% from its conventional size for 2.40 GHz microstrip antenna operated frequency antenna. The antenna produces gains of 2.5 dB at 2.415 GHz with the overall size of antenna about 35 × 26 × 1.67 mm. Simulation and optimization of the presented CSMPA produced a good results which suitable for RFID applications.

Experimental investigations of microstrip Sierspinski-Gasket fractal antenna

Fractal involves repetition patterns in an iterative manner. In this paper, the design of a set of microstrip fractal antennas is presented. The chosen configuration is the Sierspinski gasket. The antennas were first simulated and optimized. Upon achieving good performance at the desired frequency of operation of 1.575 GHz, each iterative fractal design was then fabricated using a microwave board. The antennas were then soldered with 50 ohm SMB connector at the input. Measurements were performed for one and two-port parameters. The measured antennas were found to perform well at their corresponding frequencies of operations.

Wideband Antenna with Reconfigurable Band Notched Using EBG Structure

A wideband antenna with band notch function using electromagnetic bandgap (EBG) structure is proposed. The antenna is capable of reconfiguring up to three band notch operation. Three EBGs are aligned underneath the feed line of the wideband antenna. The transmission lines over EBGs unit cells perform as a band stop filter. A switch is placed on each of the EBG structure, which enables the reconfigurable band stop operation. The simulated and measured reflection coefficients, together with the radiation patterns, are shown to demonstrate the performance of the antenna.