A solar powered UHF transponder for wildlife and low light applications

Autonomous solar powered transponders or wireless sensor nodes operate well in high sun irradiation whereas in low light conditions the efficiency of the solar cell decreases and full operation is not guaranteed any longer. This is likely to happen in wildlife scenarios particularly in shaded areas or in indoor environments. The presented transponder concept is designed to face exactly these challenging applications. This article describes the characteristic figures that have been evaluated for various different sending intervals of the transponder. The degree of efficiency for the harvested energy is optimized by using an optimum adapted maximum power point for the solar cell and thereby vastly improving the sensitivity of the system. This allows for a single-digit start-up time within minutes in low light conditions and accomplishes operation in lowest light conditions. Therefore, this transponder concept can also be applied in smart industrial indoor environments or any other low light condition scenario.