We consider an application where we want to determine the orientation of a battery-less device (a dice). The passive system is supplied with power and the communication is obtain through the change of the load, providing a short range autonomous communication and power transfer. Modeling of such system is crucial for the analysis of the task for the detection of the orientation with or without the need of sensor. The energy harvesting is one of the crucial step in achieving the goal of the such system and it is important to determine the impact of parameters such as distance, current and size in the system. Index Terms—wireless power transfer, magnetic field density, coupling factor, resonance frequency.