Design Of Internal Multiband Mobile Phone Antennas

With the development of the cellular mobile communication, mobile phones are expected to work in more wireless networks. Thus, the antennas of cell phones need to cover relevant bands, such as GSM/DCS/PCS/UMTS/ISM bands. Furthermore, mobile phones are becoming smaller and thinner, the space reserved for antennas is limited and small, added that antennas are the key link for wireless communication system, therefore designers are devoted to research about miniaturization for multiband mobile phone antennas.The main content of the thesis is summarized as follows:Firstly, the feed modes and effects of SAW(Surface Acoustic Wave) that to note in micro-strip antenna analysis are also discussed. The critical characteristic parameters as well as the most common theorem and methods in the analysis of antennas are discussed in the following part. And then the article lays its key point in debating the advantages and defects of classical PIFA and monopole antennas. Furthermore, a brief summary is made on design techniques and schemes that have been proposed.Secondly, based on the requirements for mobile phones to cover more bands and the numerous advantages of planar monopole antennas, such as low profile, small size, and easy to resonate in multiple bands simultaneously, two multiband planar monopole antennas are presented. Considering the design idea and flow, much improvement and optimization is implemented in simulation software HFSS, and the influence of the key structural parameters’ variation on antennas’ performance are also discussed. The very two antennas can achieve favourable impedance bandwidth that covers GSM/DCS/PCS/UMTS bands. The good omni-directional radiation performance and low profile makes the antennas attractive for application in practical design of mobile phones.Finally, the fundamental principles of impedence matching are elaborated, the potential merits of matching circuits and design criteria that should be followed are also discussed theoretically. Next, the design flow of matching circuits for PIFA antennas using CST and ADS are displayed. Through the very example, it is concluded that inserting matching circuits is a novel solution that may bring about remarkable improvement for antennas’ performance, in the case that when there is no way to optimize by changing the radiating structure of antennas. However, the examples also demonstrate that not all established antennas could be optimized with matching circuits. The introduction and designation of matching circuits should consider the changes it may bring to the RF performance of antennas synthetically.