Ebrahimi, Elham (2012)
Ph.D. thesis, University of Birmingham.
The growing demand for development and deployment of new wireless services has influenced the hardware design procedure including antennas and radio frequency (RF) front end, particularly in portable devices. Hence, novel solutions that are multiband, multimode, low profile, low cost and easy to integrate into the feature-rich compact devices are required.
The research described in this thesis concerns integrating wideband and narrowband functionality and therefore adding to the versatility of the antenna systems in various wireless scenarios. The integration concept is based on sharing some sections of one antenna between several other antennas. This approach may be useful in designing multimode wireless terminals while keeping the required antenna footprint small. Based on this concept a demonstrator antenna is designed and verified. The power coupling between the two modes is studied and several solutions are presented.
To demonstrate the versatility of this concept, the possibility of frequency reconfiguration is explored for narrowband mode using matching circuits with fixed elements. Wideband and reconfigurable narrowband functionality may potentially be of advantageous in emerging wireless communication systems such as software defined radio and cognitive radio for wideband sensing and reconfigurable narrowband communication procedure. Furthermore, the antenna integration within a device platform is studied. A technique is proposed to mitigate the unwanted effects of printed circuit board on the printed wideband antenna characteristics. As a result the radiation pattern, gain and group delay are stabilised across the band.
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