In this dissertation, a variety of multiband communication device antennas using the coupling-feed mechanism are presented. The coupling feed contributes additional capacitance to the antenna¡¦s input impedance which shows a high inductive component for the traditional case of using a direct feed. In the first and second antenna designs, with the coupling feed, the high input inductance of the antenna is effectively compensated. This behavior leads to a dual-resonance excitation for the lower band of the antenna. Two wide operating bands are achieved, allowing the antenna¡¦s lower and upper bands to easily cover GSM850/900 and GSM1800/1900/UMTS operation. For the last two antenna designs, owing to the coupling feed, the very large input impedance seen at antenna¡¦s lower band is greatly decreased and results in successful excitation of the one-eighth wavelength (£f/8) mode of the antenna. The specific absorption rate and hearing aid compatibility results for these mobile phone antennas are also analyzed. The effects of presence of the user¡¦s hand on the laptop computer antenna performance are also studied in this dissertation.

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.