The aim of this Thesis is in connection with a researched area nowadays at the Department of Electronic Devices, which is different solar panel defining systems. It attempts to sum up the literature concerning the field, and the achievements have done until the day. On the other hand, discusses the basics of the topic, the planning of a LED-based modular illumination unit, paying special attention to the electronic, optic, mechanic and thermal aspects. It also introduces novelties concerning the feasibility of the modular solar simulators and spectral lighting units. Despite the complexity of the given task, it wants to serve to a predefined plan concerning a LED-based modular illumination unit for the spectral response measurement on solar cells and its different modules. Finally, it poses a suggestion about a complete measuring arrangement, giving a direction to work on concerning the future developments of the subject. This work tries to list up the upcoming further developing possibilities, especially with the provided electrical circuit design together with the reported measurements validating it. Also, it tries to give a recommendation on the further continuation of the project in relation of the work of its different parts.