Measurement Data Based Study on the Intra-body Propagation in the Presence of the Sternotomy Wires and Aortic Valve Implant
This paper presents a comprehensive study on the impact of sternotomy wires and a medical implant on the ultra-wideband (UWB) channel characteristics by studying intra-body propagation in the vicinity of on-body antennas. The main contribution on this work is to verify propagation path calculations with measurement data taken from a volunteer that has sternotomy wires and an aortic valve implant and from a reference volunteer without any implants. Furthermore, the impact of sternotomy wires and the aortic valve implant is confirmed by finite integration technique simulations using a tissue layer model. It is shown, that additional signal peaks and variations of the channel impulse responses are observed for the medical implant case, since both sternotomy wires and aortic valve implant contain highly conductive materials which impacts on the channel characteristics. In the time domain simulation results, the difference between the channel strength of the implanted and non-implanted cases varies between 5–17 dB within the time range corresponding to the relevant propagation paths. This phenomenon should be taken into account when designing on-body monitoring devices and when choosing sensor node locations to avoid interference due to the additional multipath propagated signal components. On the other hand, knowledge of the impact of the aortic valve implant may be utilized in the design of devices that can monitor the functionality of a valve implant during the heartbeat.