Impact of the antenna cavity on in-body propagation and channel characteristics between capsule endoscope and on-body antenna

This paper presents a study on the impact of the antenna cavity on the in-body propagation and ultra wideband wireless body area networks (UWB-WBAN) radio channel characteristics between the capsule endoscope and the on-body antenna. The study is conducted with CST Studio Suite simulations and one of its anatomical voxel models. A simplified capsule model and two different on-body antennas designed for low-band UWB in-body communications are used in this study. The first antenna has a smaller cavity while the second antenna has a larger cavity. The radio channel characteristics between a capsule endoscope model and an on-body antenna are evaluated with the cavity and without the cavity in frequency and time domains. Furthermore, 2D power flow representations are studied to get insight how the presence and absence of the cavity changes the signal propagation within the tissues. It is found that with the antenna having a smaller cavity, the cavity impact depends on the on-body antenna location respect to the abdominal muscle layers. Instead, the antenna having a larger cavity enables to capture multipath components from the wider area resulting in stronger signal regardless where the antenna is located.