I. Introduction
Today’s global trends in mobile industry is smaller, lighter, and thinner devices. Many RF engineers are working on part miniaturization to satisfy these increasing demands. Antenna size is an important factor for reducing the overall size of the mobile device. Some mobile devices have multiple antennas in one device in order to translate signals in a different frequency range such as Global System for Mobile Communications 850/900 MHz or Long-Term Evolution 1700/2100 MHz at once, and therefore, a small antenna with good performance is necessary. Decreasing the antenna size is very challenging because the antenna size is determined by its electrical length and the antenna performance is also bounded by fundamental limits depending on the size. One method for reducing the antenna size is by changing the geometry of the antenna. By bending or meandering the current path of antenna, total area or volume can be decreased. Another common method for antenna miniaturization is to increase the relative permittivity of the substrate since the antenna size is inversely proportional to , where is the relative permeability [1]. However, increasing of the substrate results in increase in stored electric energy inside the substrate, which leads to a narrow bandwidth and low efficiency [2]. On the contrary, magnetodielectric (MD) materials that have and greater than 1 can be used to miniaturize antenna size without deteriorating antenna performance too much [3]. Furthermore, by increasing ratio, the antenna performance can be improved more with the same size of antenna [4]. This is just one application of MD materials discussed in this paper.