Performance Degradation of an Uncooled Coaxial Monopole Antenna: A Preliminary Investigation of PTFE Expansion at Ablative Temperatures

During microwave tumour ablation, the antenna's performance primarily depends on the material properties of the surrounding tissues. This is mainly due to the temperature-dependent dielectric permittivity and effective conductivity. Active cooling is commonly employed within microwave ablation applicators. However, there is emerging interest in uncooled applicators with simpler designs. This study shows how the elevated ablation temperatures will adversely impact the structure and, consequently, the performance of the coaxial-based uncooled antenna. It was determined that this is primarily catalysed by the thermal expansion of the Polytetrafluoroethylene (PTFE) dielectric, which decreased the antenna's return loss. Moreover, this investigation proposes an adequate ablation temperature operating region where the uncooled antenna structural changes will marginally affect its performance.