Comprehensive study on the impact of sternotomy wires on UWB WBAN channel characteristics on the human chest area

Abstract

This paper presents a comprehensive study on the impact of the sternotomy wires on the characteristics of ultra wideband (UWB) radio propagation channel in the human chest area. The study is conducted using two simulation models: a planar layer model and a three-dimensional elliptical layer model. The study includes antennas designed for on-body and in-body communications. Furthermore, the measured data and propagation path calculations are presented to verify the simulation results. The main purpose is to show how the steel wires affect the on-body channel characteristics and in-body propagation within the tissues when the monitoring antennas are located in close vicinity of the human body. The study is conducted by evaluating: 1) channel characteristics in both frequency and time domains; 2) 2D power flow figures; and 3) Poynting vector values. Furthermore, the impact of the fat layer thickness on the visibility of sternotomy wires is studied. Moreover, the impact of sternotomy wires is studied for the case of the recently operated patient, for which the sternotomy wires are on the sternum bone surface, as well as for the case where the sternotomy wires are embedded into the sternum bone. It is found that sternotomy wires have a clear impact on the channel. The strength of the impact depends on the antenna types used by the monitoring devices, the thickness of the fat layer in the sternum area, and whether the sternotomy wires are on the sternum surface or whether they have already been embedded on the sternum as it happens with time.