This paper presents a study on the radio channel characteristics between an endoscope capsule and an on-body antenna in different parts of the small intestine with different onbody antenna location options. The study is conducted using finite integration technique based electromagnetic simulation software CST and one of its anatomical voxels. An endoscope capsule model with a dipole antenna is set inside different areas of the small intestine of the voxel model. A recently published highly-directive on-body antenna designed for on-in-body communications is used in the evaluations. Different rotation angles of the capsule are also considered both with a layer model and a voxel model. It is found that radio channel characteristics vary remarkably depending on the antenna location in the small intestine and location of the on-body antenna. Thus, the on-body antennas should be located carefully to ensure coverage over the whole intestine area. However, the path loss does not only depend on the distance between a capsule and the on-body antenna but also on the tissues between the capsule and onbody antennas. Furthermore, orientation of the capsule has also strong impact when linearly polarized antennas are used.

The paper introduces a novel antenna operating in the UWB band 3.75-4.25 GHz for BAN (Body Area Networks) applications. The proposed antenna has omnidirectional and directional radiation patterns in absence and presence of a backed air-filled cavity, respectively. The antenna was simulated using CST Microwave Studio software, showing maximum realized gains of 2.6 and 7.37 dB with and without the cavity, respectively. The designed antenna is planned to have the role of a receiving antenna for wireless capsule localization purposes. Therefore, an initial on-body study was required and detailed in this paper giving the focus on the small-intestine area, since it is the vital human body part of interest for capsule tracking and monitoring. An onbody scenario is presented using two antenna structures and compared with the free-space results. SAR (Specific Absorption Rate) is also investigated in compliance with IEEE/IEC 42704-1 standard. These initial studies prove that the antenna can be regarded a good candidate for WCE (Wireless Capsule Endoscopy) localization.

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.

This paper presents a comprehensive simulation and measurement data based study on the UWB on-body radio channel characteristics on the human abdomen area. The main target is to evaluate channel characteristics with several different antenna location options using a recently published ultra wideband (UWB) antenna designed for inbody communications, e.g. for capsule endoscope localization. For the simulations, we use two voxel models and two layer models. Measurement data consists of channel data for seven volunteers having different body size and body composition. The simulation and measurement data is compared and the reason for the differences is discussed. Furthermore, it is shown that the on-body channel characteristics vary significantly depending on the body size and shape of the volunteer if the antenna separation distance is large. With smaller antenna distances, the difference is minor.

This paper presents a study on the fat in the abdomen area as a propagation medium in wearable and implant communications systems. Propagation via subcutaneous and visceral fat is considered separately. Simulations and measurements are done for both female and male bodies with the on-body antennas designed for in-body communications. Propagation paths are calculated and compared with the simulated and measured impulse responses. Furthermore, we analyze simulated 2D power flow figures, which illustrate the propagation inside the different tissues. It is shown that the signal propagates through the fat layer with minor losses compared to the other tissues of the studied cases. The signal propagates through the fat tissue from the abdomen area to the backside of person with 60 dB power loss. Additionally, the calculated fat layer propagation paths match well with the peaks of the simulated and measured impulse responses. The information about the fat as propagation medium is useful when designing the wireless and wired medical and health monitoring devices.

This paper presents a simulation based study on the impact of the antenna-body distance on the ultra wideband (uwb) on-body radio channel characteristics. The antenna used in this study is a recently published highly directional cavitybacked uwb antenna, designed for inbody communications, e.g. capsule endoscope localization. The on-body channel characteristics are evaluated both in frequency and time domains with several antenna-body distances as well as with several antenna location options. Furthermore, the impact of the antenna-body distance is evaluated by studying 3D power patterns, which also provide information about the propagation depth within tissues in different antenna-body distances. It is shown that antenna-body distance has a significant impact on the on-body channel characteristics. In time domain the difference can be 15 dB between the main peaks of the impulse responses whereas in frequency domain, the path loss difference can be even 30 dB within the frequency band of interest. Besides, antenna-body distance has a clear impact on the propagation depth inside the tissues as well.

This paper gives an insight of an on-body study using Low-UWB (lowest mandatory UWB band of IEEE 802.15.6 standard) directive antennas. Investigations are first carried out by simulations with male and female voxel models with different antenna body separation distances. The antenna performance is assessed in close proximity to a human body in terms of return loss, impedance matching, directivity, realized gain and efficiencies. The on-body matching results were confirmed by measurement with different real persons. Later, a free-space propagation study was conducted to assess the farfield antenna performance and to serve as a reference for onbody studies. Finally, an on-body propagation study is presented for different antenna positions with different separation distances from the body.

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