A study on miniaturization of 900 MHz and 2 GHz band antennas utilizing magnetic material

Built-in antennas are becoming a more intense requirement for cellular phone handset antennas. Many studies on miniaturization of the antenna using dielectric materials have been reported. However, lately, the use of magnetic materials has been considered for an electromagnetic shield and a radio wave absorber. Furthermore, low loss magnetic materials, which can be used for higher frequency bands, have been developed. A technique is studied for downsizing handset antennas at the 900 MHz and 2 GHz bands using a magnetic material. A planar inverted-F antenna (PIFA), which is the popular handset built-in antenna, is used. Firstly; basic characteristics such as input impedance, current distribution and radiation patterns are obtained, and calculated results are compared with measured results. Secondly, the change of resonance frequency obtained by arranging various types of magnetic materials is examined. Suitable configurations and arrangements of magnetic materials are also examined. The possibility of miniaturization by using magnetic materials is confirmed; approximately 50% miniaturization of the PIFA is possible at the 900 MHz and 2 GHz bands.. The electromagnetic simulator HFSS, which can consider magnetic loss, is applied to calculate VSWR and radiation patterns.