Built-in Multi-frequency Broadband Miniaturized Cell Phone Antennas

The main work of this thesis is about the study of the internal handset antennas. In recent years, with rapid development of mobile communications, the demand for mobile handsets with miniaturization, multi-band and broadband is presented, so how to design handset antennas meeting the performance are the hot topic in nowadays.In this thesis, firstly, basic principle of electrically small antennas is introduced, and the inherence limitations of electrically small antennas and the resolve methods are analyzed. Then the theoretical analysis of planar antennas, main including planar monopole antenna and planar inverted-F antenna (PIFA) that have recently received much attention for application in mobile communication systems, are studied in detail in this thesis. And this thesis summarizes the technologies of miniaturization, multi-band and broadband of the planar handset antennas, especially including the technologies of multi-band and broadband of microstrip antennas.In this thesis, three compact internal multi-band monopole antennas (GSM/DCS/ISM, GSM/DCS/PCS and GSM/DCS/PCS/WCDMA) and one dual-band PIFA (WCDMA/ISM) are presented. Simulated results are computed by the software Ansoft HFSS. And the influence of correlative dimension parameters and user interaction are discussed along with the simulated results.The GSM/DCS/PCS monopole antenna is made and measured, and a good agreement between measurement and simulation is achieved. From the experimental result of the GSM/DCS/PCS monopole antenna and the simulated result of four handset antenna, these antennas have enough bandwidth for covering operation bands according return loss less than -7.5 dB (VSWR < 2.5), have approximately omni-directional radiation characteristics, and the gain lager than OdBi. And these monopole antennas occupy small volume less than 40×10×5 mm~3, and the PIFA less than 40×10×7 mm~3. So these antennas suitable for new generation mobile communication applications, and should be have good applications.At last, we summarize the research of the thesis and propose some needed improved problems ulteriorly.