Ismahayati Adam

Effect of different substrate materials on a wearable textile monopole antenna

In this paper the investigation of the effect using different substrate materials on a textile monopole antenna is discussed. This textile monopole antenna is designed to be used for Body-Centric Wireless Communications (BCWC) at 2.45 GHz. Three types of non-conductive materials were selected: felt, fleece and foam. The textile monopole was benchmarked against a conventional FR-4 monopole antenna. The results demonstrated a good agreement between simulated return loss of all three substrates used for textile monopole antenna and conventional monopole antenna. The felt-based textile monopole antenna offered higher return loss compared to other substrates and conventional monopole antenna. Moreover, the substrate materials gained bandwidths of up to 1000 MHz in free space where fleece fabric produced broader bandwidth compared to other substrates. The simulated gain characteristics for all three types of substrates agreed reasonably well with conventional monopole antenna.

Design of a flexible Minkowski-like pre-fractal (MLPF) antenna with different ground planes for VHF LMR

This work investigates the suitability of a flexible Minkowski-like pre-fractal antenna (MLPF) for application in the Very High Frequency (VHF) Land and Mobile Radio (LMR) frequency bands (136–174 MHz). The proposed center-fed, third iteration antenna has been manufactured using both copper tape and Shield It Super, a conductive textile. It has been tested on four types of ground plane, i.e. rectangular, fractal Minkowski, meander line and L-shaped. It is observed that an L-shaped ground plane performs the best, and provides an additional frequency tuning parameter to the overall structure. Simulated and measured S11 show a good agreement and the proposed antenna is working within the desired frequency range. A simulated gain and efficiency of more than 1.9 dB and 76 %, respectively, are obtained. The measurement in a Satimo SG64 anechoic chamber provided 0 dB gain and about 48 % efficiency.

Basic characteristics of a textile monopole antenna for body-centric wireless communications

This paper presents a light-weight, compact and simple textile monopole antenna structure for body-centric wireless communications (BCWC), applications operating in the 2.45 GHz Industrial, Scientific and Medical (ISM) band. Three different conductive textile materials are chosen: Pure Copper Polyester Taffeta, ShieldIt Super and Nora RS. The result obtained in this investigation showed that all three textile monopoles produced higher reflection coefficient and directivity values compared to the conventional FR-4 monopole antenna. It was found that the simulated gain and radiation pattern characteristics agreed well with the conventional FR4 monopole antenna. The result has also shown that the Nora RS gave better performance in terms of return loss and gain characteristics compared to the other two electrotextiles.

Comparison of rectifier performance using different matching technique

This paper describes the design and implementation of the 4-stage Villard multiplier for RF energy harvesting. Each stage is a combination of two HSMS 2850 Schottky diodes and two capacitors for each stage. For ambient energy harvesting, the incident power is extremely small, thus an efficient rectifier is needed. The designed rectifier with the matching circuit is a good candidate since it is able to enhance the rectified output power up to 300% during -40dBm input power compared to the rectifier circuit alone.