Endah Komalasari
Department of Electrical Engineering, Faculty of Engineering, Lampung University, Bandar Lampung 35145. *Correspondence to Endah Komalasari, email: endah.komalasari@eng.unila.ac.id. Tel.:+62-721-704947; fax.:+62-721-704948.
Indonesia

Rahmattulloh Rahmattulloh
Department of Electrical Engineering, Faculty of Engineering, Lampung University, Bandar Lampung 35145.
Indonesia

Herri Gusmedi
Department of Electrical Engineering, Faculty of Engineering, Lampung University, Bandar Lampung 35145.
Indonesia