Conductive layer under a wearable UWB antenna: Trade-off between absorption and mismatch losses

A common problem with wearable antennas is the influence of body tissues: they decrease the performance of an antenna due to detuning and electromagnetic absorption. From the wearable device point of view, a ground plane can mitigate the absorption although its difficult aspects on antenna operation are admitted in the field. For ultra wideband (UWB) radiators, impedance behaviour is conceded to be sensitive to the shape of an antenna. Therefore, taking a ground plane into account into a design might involve huge challenges for the proper matching as well for other parameters. The present paper considers the impact of a conductive layer in between skin tissue and broadband dipoles. The effect of the layer on antenna operation is considered by separating the proportion of body, absorption and mismatch losses. The conductive layer is observed to be useful when the absorption is required to decrease, since the layer reduces those losses up to 10 dB in the lowest frequencies. Nevertheless, the benefit is profitable only if caused mismatch can be compromised or an antenna is co-designed with a ground plane. This is because mismatch losses are increased simultaneously as demonstrated in this paper. The separation of the loss parameters for the co-design of a layer and antenna is the next step of this work for various configurations.