In this dissertation, EMC antennas for mobile communication device applications are proposed. This kind of EMC antennas can overcome the problem that happens to the conventional antenna; in practical application, when electronic components are placed very close to the conventional antenna, large degradation of the antenna performance will occur. In the proposed EMC antennas, by adding a vertical antenna ground plane functioning as a shielding metal wall, EM coupling between the EMC antenna and nearby components can be reduced. Thus, it leads to no degradation or only negligible variations of the antenna performance. Also, the concept of EMC antennas can be applied to the monopole antenna. One of the examples suitable for the future thin (< 10 mm) mobile communication device is demonstrated. Further, the user¡¦s hand effects on EMC antenna performance are analyzed. Even when the mobile phone is hand-held at the bottom, large radiation efficiency drops are observed, especially for the GSM band.

In this dissertation, thin internal antennas for mobile communication devices with a total thickness of less than 10 mm are proposed. There are mainly two differences in the antenna¡¦s construction between the proposed thin internal antennas and conventional planar inverted-F antenna. The first proposed antenna for thin internal antenna is a combo type formed by combining the conventional inverted-F antenna with the monopole antenna. The second proposed antenna is obtained by integrating two radiating arms into a radiating patch. By adjusting the tapering angle and the direction of the end portions, thin internal planar antenna with a thickness of less than 4 mm can be successfully achieved. In these two antennas, their Q-value can be lowered, and then the impedance bandwidth can be effectively improved. This kind of thin internal antennas not only has good impedance matching but also shows good radiation performance. Additionally, by adding a vertical metal wall acting as a RF shielding wall, EM fringing fields between the thin internal EMC antenna and nearby metal components can be effectively supressed. This kind of EMC antennas can effectively eliminate the isolation distance between the antenna and nearby conducting elements to increase the available space on the printed circuit board for additional functions. Besides, multi-band operation is another important function in current mobile devices. In this dissertation, we also studied the effects of the plastic casing and the user¡¦s hand and head on the antenna charateristics. For studying the antenna with the presence of the user¡¦s hand and head, the simulation model provided by SPEAG simulation software SEMCAD is used. From the results obtained, it is seen that the frequency detuning is greatly dependent on the presence of the user¡¦s hand and head. Owing to the presence of the user¡¦s hand and head, large decrease in the radiation efficiency is seen. It also indicates that the radiation efficiency decrease and radiation pattern distortion are mainly owing to the radiation power absorption by the user¡¦s hand and head.