Propagation study of UWB capsule endoscope with multiple on-body antennas

Abstract

This paper presents a study of the radio channel characteristics between a capsule endoscopy and a multi onbody antenna system on ultra wideband wireless body area networks (UWB-WBAN). Multiple on-body antennas are required to provide reliable communication link between the capsule and the on-body device, but also essential for capsule localization. The main aim is to study the variation of the frequency and time domain channel characteristics for the selected on-body antennas in different capsule locations, including the most challenging capsule locations deep inside the tissues or far away from most of the antennas. This study also evaluates whether five of selected type directive on-body antennas is enough to cover the intestine area thoroughly. The study is conducted with CST Studio Suite simulations and one of its anatomical voxel models. A simplified capsule model and a directive on-body antenna designed for low-band UWB inbody communications are used in this study. It is found that five of this type directive on-body antennas provide sufficient coverage over the intestine area even in the most challenging capsule locations. In certain capsule locations, the variation between the channel attenuations can be significant, over 40 dB within the frequency range of interest, if the capsule is located deep inside the tissues without smooth access to outer fat layer through which the signal could travel easily to different on-body antennas. Instead, if the capsule is located close to the subcutaneous fat layer, the channel attenuation is moderate even for the antennas which are located far from the capsule.

Radio Channel Study for Colon Capsule Endoscopy with Low-Band UWB Multiple Antenna System

“…The antenna has a cavity (grey area in the antenna) to enhance the directivity towards the body. Originally, the antenna was introduced in [14] and it has been later used in several in-body channel studies in [3], [11], [15]. Realized gains of the antenna as it is located on the body, are presented in Figs.…”

“…Previously, capsule endoscopy has been targeted mainly on the detection of abnormalities in the small intestine area since the small intestine is not easily achieved with traditional endoscopes [1]- [3]. In recent years, interest on colon capsule endoscopy has increased remarkably since the majority of the intestinal tumors are located in the colon area [4]- [6].…”

“…Recently, it has been recognized that ultra wideband (UWB) technology could provide several advantages for capsule endoscopy, such as high resolution images, high data rate, low power, and reliability [3]. These are essential features especially for future's active capsules.…”

“…These are essential features especially for future's active capsules. However, one of the main challenges related to UWB based capsule endoscopy, or in general UWB implant communications, is the high propagation loss in the tissues [3], [7].…”

“…Previous UWB capsule channel modeling studies focus mainly on small intestine area. This paper is continuation for [3] by presenting radio channel evaluations between the capsule endoscope and multiple directional receiving on-body antennas in different capsule locations in different parts of the colon area of a realistic voxel model. The novelty of this research is that, up to author's knowledge, other UWB capsule endoscope studies do not evaluate radio channels throughout the colon area using an anatomical voxel model and multiple directional on-body antennas.…”