The growth of the Internet of Things (IoT) requires that a large number of devices need wireless connectivity. For this reason, a simple and fast method capable of designing multiband antenna systems, utilizing a very simple antenna element is proposed. In this method the antenna is seen as an impedance box where a multiband matching network with lumped components is the one that fixes the number of frequency bands. The multiband matching network was designed in Optenni Lab based on the measured antenna input impedance and the EM-simulated radiation efficiency. To validate the procedure, a multiband antenna system operating at 824MHz-960MMHz and 1710-2690MHz is implemented. The matching network has been obtained through a fully automated process without human intervention and without any type of adjustments. This enables the design of multiband antenna systems in a quick, easy, and systematic way.