Roshayati Yahya

1.575 GHz Circular Polarization wearable antenna with three different substrate materials

This paper presents an analysis of a Left-Handed Circular Polarization (LHCP) wearable antenna with different textile material (substrates) for Global Positioning System (GPS) application. The proposed antennas have achieved circular polarization (CP) by truncating two opposite edged of the square patch for all designed antennas with three different substrates. The analysis is focusing on using felt, jeans and cotton as substrates while maintaining shieldit supper as a conductor. The performance comparison have been made on the simulated reflection coefficient (S11), axial ratio (AR), bandwidth and gain. The results show that jeans fabric attained a better reflection coefficient of -41.36 dB at 1.575 GHz as compared to the other materials. Besides, the jeans has achieved good AR bandwidth of 17 MHz, followed by felt with AR bandwidth of 16 MH and cotton with AR bandwidth of 13 MHz.

New wideband textile antenna for SAR investigation in head microwave imaging

In this paper, a wideband textile antenna for microwave imaging is presented. The antenna operates from 1.2 to 6 GHz at -10 dB level of the reflection coefficient magnitude. Whilst, the transmission coefficients of the two antennas are lower than -20 dB level. The SAR value when only one antenna is attached to the head phantom has been investigated. In addition, the maximum value of SAR is also obtained when two antennas are attached to the head phantom. The results show that the SAR levels are 0.047 W/kg and 0.022 W/kg at averaged 10 g tissues, respectively. Due to the values of SAR are far below the standard limit, thus this antenna is suitable to be used for microwave imaging.

Effect of Rainwater and Seawater on the Permittivity of Denim Jean Substrate and Performance of UWB Eye-Shaped Antenna

The effect of rainwater and seawater on the permittivity of denim jean substrate and performance of an ultrawideband (UWB) eye-shaped textile antenna is investigated in this letter. For the simulated and measured reflection coefficients in dry condition, it was found that the antenna operates at 2.4-10.9 and 1.6-12 GHz, respectively, with the simulated gain between 3.2 and 5.8 dBi from 2 to 12 GHz with efficiencies greater than 50%. The antenna can operate at the entire range in dry conditions when S11 ≤ -10 dB, but with limited performance under wet conditions. However, it cannot be used when immersed in rainwater and seawater. From the investigation, it can be shown that the permittivities of denim jean substrate under wet and immersed conditions are proportional to the permittivities of the absorbed medium (rainwater or seawater) at 2-12 GHz.

Eye shaped fabric antenna for UWB application

This paper presents a fully fabric Eye shaped antenna for Ultra-wideband (UWB) applications. The effect of using cutting slots on the ground plane is investigated. By using Coplanar Waveguide (CPW)-fed, the implementation of a semicircular and two triangular cutting slots have improved the antenna bandwidth. Details of the Eye shaped antenna design and simulated and measured return loss results are presented.

Circular Polarization Textile Antenna for GPS Application

A right-handed circular polarization (RHCP) textile antenna for Global Positioning System (GPS) application is proposed. The circular polarization (CP) is achieved by truncated two opposite edged of the 84 mm square patch. The proposed antenna design use a shieldit super as the radiator and felt fabric as substrates. Such presented antenna attains a good bandwidth of 90 MHz from 1.53–1.62 GHz. Besides, the antenna is capable to perform an axial ratio of less than <3 between 1.56 and 1.62 GHz which covered the GPS operating frequency of 1.575 GHz. Moreover, this paper discussed the parametric study of the truncated patch in order to achieve CP. The simulated result shows that the presented antenna is potential for point-to-point wireless communication system.

Initial determination of object locality using reflection pulse

Initial locality determination using a container of water is presented. The relative permittivity of water is detected by the propagating microwave signal that travels from the antenna to the water container. The amplitude that represented in time domain indicates the reflection pulse. Therefore, the location of water that located at 30, 60, and 150 mm away from the antenna is initially determined using the reflected pulse.