Research On Compact Multiband And Broadband Mobile Phone Antennas For 4G Communications

With the rapid development of mobile communication technology, mobile devices are moving towards multi-functional and multi-standard communications network. As an important device to transmit and receive electromagnetic waves, antennas will directly affect the quality of communication. Because of the excellent feature of small size and wide operating bandwidth, electrically small antenna has been widely used.The basic theories and analysis methods of the mobile phone antennas are discussed, and the widely used methods of miniaturization, multi-band and broadband are also summarized in this thesis. With the design processes and methods of smart phone antenna, two novel miniaturized, multi-band and broadband antennas are presented and summarized as follows:Firstly, a seven-band mobile phone antenna with a closed metal frame is designed. The antenna can effectively reduce the impact of signal shielded by the closed metal frame on the traditional mobile phone PIFA antenna and the monopole antenna. With the theories of slot antenna, the metal frame is designed to be part of mobile phone antenna. As a result, an antenna with high practical value is proposed for GSM850,GSM900, DCS1800/PCS1900/UTMS2100/LTE2300/LTE2500 operation bands.Secondly, an eight-band frequency reconfigurable mobile phone antenna with a small size of 43 mm × 9 mm × 3 mm is presented. The antenna is composed of an RF switch, a coupling strip and a loop feeding strip. By choosing different values of inductances connected to the ground plane through the RF switch, the effective electrical length of the antenna can be changed. In this way, the generated four statuses have broadened the impedance bandwidth significantly in the lower frequency. The designed antenna can cover the 2G、3G and 4G communications networks and have a good efficiency and the average gain.In general, the two designed mobile phone antennas have an excellent performance in simulation and measurement. They have not only a good impedance matching but also an omnidirectional radiation pattern. The average gain and efficiency meet the practical requirements well, which indicates that the designs can be a good choice to apply to smart mobile devices.