Due to the rapid increase in the demand of wireless communications, the limited and valuable frequency spectrum has become congested in the lower frequency bands. Several methods can be used to overcome these problems. Novel techniques based on ultra-wideband (UWB) wireless communications operating in the 3.1-10.6 GHz can be used to overlay our existing users and thereby reusing spectrum. Spectrum can be used more efficiently by employing diversity or MIMO systems and finally multibanded systems can access and use more systems. In this thesis we propose antenna solutions for each of these new techniques....[ Read more ]

Due to the rapid increase in the demand of wireless communications, the limited and valuable frequency spectrum has become congested in the lower frequency bands. Several methods can be used to overcome these problems. Novel techniques based on ultra-wideband (UWB) wireless communications operating in the 3.1-10.6 GHz can be used to overlay our existing users and thereby reusing spectrum. Spectrum can be used more efficiently by employing diversity or MIMO systems and finally multibanded systems can access and use more systems. In this thesis we propose antenna solutions for each of these new techniques.

UWB antennas based on planar monopole are investigated with 75% fractional bandwidth and miniaturized size. Then, a dual band, dual diversity Sierpinski gasket antenna with two feed ports as well as a single band, triple diversity rectangular patch antenna with three feed ports are presented. The significance of the antennas is that they can provide dual signal diversity for communication systems at two different frequency bands or three-branch diversity for single frequency operation. Experimental results are presented for the designs that operate at 1800MHz and 3900MHz for the gasket and 3400MHz for the patch. As an additional issue we also investigate the impact of diversity antennas on SAR.

A novel design for a five-band planar inverted-F antenna (PIFA) operating at 900, 1950, 2430, 3150 and 5000MHz is presented. The five bands of operation are achieved by employing three L-shaped slots and a parasitic element above the main patch. The dimension of the antenna is about 1520mm² that is comparable with the size of PIFA at 900MHz with thickness of 12mm.