A Novel UWB Antenna for Wireless Body Area Networks

• Main Authors: Kang, Cheng-Hung, 康鉦浤
• Other Authors: Tarng, Jenn-Hwan
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/53715072380705708192

碩士 === 國立交通大學 === 電信工程研究所 === 98 === Wireless Body Area Network (WBAN) is wireless sensor network which is applicable on the human body. The sensors, which are applied on the human body, transmit the wanted/desired signal to the center devices for remote monitoring. The sensor devices are placed on the human body so there are three requirements for the antenna (which is integrated with the sensor device): 1. Compact form and low height: The antenna should be unobtrusive when it is placed on the human body in order to avoid interfering in the human’s daily activities. 2. Low mutual effect between the antennas and the human body: The antenna should keep the characteristics such as operating bandwidth when applying to the body. 3. Low backward (direction to the human body) radiation: In order to decrease the Specific Absorption Rate and increase the radiation efficiency. Owing to these three restrictions on antenna characteristic, designing an UWB antenna for WBAN is a challenge. In this thesis, we propose a novel patch-like UWB antenna used in WBAN application. The proposed antenna consists of a bevel edge fed structure and a truncated radiator. The bevel edge of the fed structure is designed for slow impedance variation and achieves very wide bandwidth. The patch-like radiator is designed for reducing the backward radiation and results in the directional radiation patterns. Moreover, the folded strip of the radiator is a key factor in antenna design, it affect the impedance match of the desired bandwidth. By suitable designing the folded strip, the return loss is over 10dB condition within the operating bandwidth. In this thesis, we also compare the measured return losses of the proposed antenna in free space and on the human body. In order to obtain the SAR values, the muscle models are employed in simulation. In order to avoid interfering the existent wireless application such as WLAN, a meander slit, a band-stop resonator, is designed at the fed structure of the proposed UWB antenna. The additional slit creates the band-rejected property while keeping the other characteristics almost the same. We can control the notch property including frequency and bandwidth by adjusting the length and distance of the slit. In final design, the band-rejected property is designed in 5GHz ~ 6GHz to prevent the interference from the WLAN.