Experimental Study on the Dependence of Antenna Type and Polarization on the Link Reliability in On-Body UWB Systems

Abstract

Abstract-An experimental study on the use of ultra-wideband antenna systems (3.5-4.5 GHz) on the human body for wireless body area network (WBAN) applications is conducted. It has been found that the link reliability can be improved and transmit power can be reduced by properly selecting the transmit and receive antennas with different radiation properties (omni-directional, directional, pattern diversity) and polarizations (vertical and horizontal) at each location on the body. Moreover, when there is blockage by the body, it may be possible to achieve better transmission when the antennas are horizontally polarized. Also, antennas with pattern diversity can be used to enhance the overall reliability of the communication system. In order to eliminate the use of cables in the measurements, an on-body UWB system has been developed and the reliability can be assessed more practically in terms of the peak amplitude of the received waveform and the bit error rate. It has been observed that when the link quality is improved, the transmit power can be reduced by more than 20 dB without compromising on the reliability, which will conserve the battery power.Index Terms-Antennas, bit error rate, diversity, propagation measurements, RF transmission, ultrawide band, wireless body area network.

User Influence on Polarization Characteristics in Off-Body Channels

“…Based on measurements [8]- [10] and Electromagnetic (EM) simulations [11]- [13], the antenna efficiency is reported to be strongly impacted by the body for separations below 8 mm, while this impact is negligible when the antenna is more than 15 mm away from the body. Moreover, different body types [10], [14] and on-body antenna locations [15]- [19] have a clear impact on the radiation characteristics. In addition to the de-tuning effect as the resonant frequency is shifted [8], [19]- [21], the antenna bandwidth also changes in the proximity of the body [8], [19]- [23].…”

“…Antenna polarization and its impact on body area propagation has been studied, e.g., in [2], [8], [29], [30]. The influence of the body on wearable antenna polarization is the least explored aspect, with only a few preliminary studies available in literature [15], [31], [32]. With antennas operating on the body, the off-body transmission coefficients in channels established with vertical (V)-and horizontal (H)-polarized off-body antennas are observed to change compared to the free space case, due to polarization mismatch losses [8].…”

On-body Cavity-Backed Low-UWB Antenna for Capsule Localization

“…Last decades, many works have been oriented towards this kind of research topic by using different frequency ranges [9,10]. However, the low Ultra Wideband (UWB) band (3.75-4.25 GHz) is defined originally in IEEE 802.15.6 standard [11][12][13] and it is preferred to minimize the path loss caused by lossy human body tissues. Additionally, to improve the image resolution quality, the requirement is to assess the captured images from inside the small intestine.…”

A novel, low-profile, directional UWB antenna for WBAN

“…These results were compared to an omnidirectional disc planar monopole. An experimental study on the dependence of antenna polarization on the UWB antenna's performance was presented by [7]. Three types of UWB antennae were used to measure the effects of human bodies and the antennae were placed in the users' hands, head and chest in different orientations.…”