This paper presents numerical and experimental study of the influence of various types of simplified human equivalent phantoms and actual human body on the reflection coefficient and bandwidth of a miniature ultra-wideband antenna. Four multi-layered body models, with different geometries and cross-sections, along with both dispersive and non-dispersive characteristics have been used in the analysis. A sensitivity analysis of the UWB antenna to the distance from the body models and their sizes has been provided to assess the most suitable model in terms of accuracy and computational time. Measurements have also been carried out with the antenna placed in close proximity to a real human test subject and results have been compared.