See, C. H., Abd-Alhameed, R. A., Zhou, D., Ramli, K. N., Mcewan, N. J., & Excell, P. S. (2010). Folded and slotted internal antenna design for 3G IMT-2000 mobile handsets. Microwave and Optical Technology Letters, 52, 1549-1553. https://doi.org/10.1002/mop.25271