The distortion of the antenna is very critical problem which must take into account for deal with the frequency characteristic of the antenna for partial discharge diagnosis in transformer. The complex form of Friis' equation is present to analyze the Fresnel region of the antenna. The original form of Friis' equation is normally applied in the far field zone. This study considers the complex form of Friis' equation in the transformer, however, the environment in the transformer may not satisfy with the distance conditions according to the Fresnel region. Nonetheless, in this paper, the evaluation of antenna performance in Fresnel region is discussed.
