Design of Compact Multiband Antennas for Portable Wireless Transceivers

Ahmad Rashidy Razali (2012). Design of Compact Multiband Antennas for Portable Wireless Transceivers PhD Thesis, School of Information Technol and Elec Engineering, The University of Queensland.

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Author Ahmad Rashidy Razali
Thesis Title Design of Compact Multiband Antennas for Portable Wireless Transceivers
School, Centre or Institute School of Information Technol and Elec Engineering
Institution The University of Queensland
Publication date 2012-01
Thesis type PhD Thesis
Supervisor Dr Amin Abbosh
Dr Marco Antoniades
Total pages 267
Total colour pages 53
Total black and white pages 214
Language eng
Subjects 100510 Wireless Communications
100501 Antennas and Propagation
Abstract/Summary In recent years, the rapid expansion of wireless communications and the consequent introduction of new frequency bands have increased the demand for multiband transceivers. For manufacturers, the multiband transceivers have to feature compact sizes and low fabrication costs. In addition, from the technical point of view, the RF front-end module of the receivers has to be easily integrated with embedded antennas that should be unobtrusive in appearance. To fulfil all these requirements, considerable attention is given to planar or microstrip patch antennas because they are easy to manufacture, and offer considerable flexibility with regards to the space constraints in RF front-end circuitry, which is primarily fabricated on Printed Circuit Boards (PCB). However, as the transceiver modules become more compact, this type of antenna faces a number of challenges. It has to achieve a multiband operation in the smaller volume that is available in modern compact wireless transceivers. To meet these goals, a suitable design methodology has to be used. This thesis work focuses on compact multi-band patch antennas which are designed for existing wireless services including GSM, PCS, DCS, GPS, UMTS, WLAN and WiMAX bands. The present techniques available in the open literature include the modification of the main radiator via bending, folding, meandering and wrapping. Each approach offers different advantages and disadvantages depending on the required application. The constraint for the lower band generation is the main challenge in radiator miniaturization. The quarter wavelength radiator subjected to miniaturization may suffer from limited bandwidth and low radiation efficiency. Alternative approaches using modifications of the ground plane are a promising technique, which were often previously overlooked by antenna designers. It is shown herein that the introduction of a ground slot at its quarter wavelength electrical dimension excites new resonances. Proper dimension and configuration design results in a minimal usage of ground plane area, which is traditionally dedicated for electronic circuitry in the transceiver module. The introduction of a ground slot in a finite antenna ground plane can be further extended to include reconfigurable features. With easily available electrical switches such as MEMS, varactors or PIN diodes, ground slots can be turned into a frequency-tuneable element. Thus, such antennas offering compact size with multiband capability can be promising candidates for wireless antenna design. This thesis presents a viable solution and a promising approach to address these challenging scenarios in antenna design. As compared to the previously published antennas in the literatures, the reported antennas present several multiband solutions by utilizing the ground slot, slit and cut instead of the conventional radiator modifications. In addition, the antennas are modified using several novel techniques to miniaturize the main radiator, such as a meandered-tail and folded quarter ellipse configurations. Finally, the thesis proposed a novel reconfigurable ground slot which eliminates the need to have a complicated bias network commonly faced in designing reconfigurable radiators. Five novel antenna designs are presented in the thesis. Initially, a compact 6 x 13 mm coplanar inverted-F antenna (CIFA) with ground slots is developed to produce a multiband operation for WLAN 2.4 GHz, 5.2 GHz and 5.8 GHz services. The antenna is the first in the literature to utilize the coupling configuration between ground slot and microstrip feedline to introduce a new resonant frequency, and thus to achieve a multiband operation. In addition, a compact 13 x 60 x 5.6 mm antenna based on a novel quarter-ellipse monopole design is also presented. In the design, the modification of the ground plane involves the use of a ground cut and a parasitic element. The resulting antenna has ultra-wideband coverage for all wireless services ranging from the GSM 850 MHz up to WLAN 5.8 GHz, the first planar antenna within 5 mm height to achieve this coverage performance. The design of a 3 mm inverted-F antenna to cover GSM, DCS and PCS operation is also proposed. This 3 mm antenna height is the slimmest dual band PIFA ever proposed in the literature. This compact 40 x 10 mm antenna radiator makes use of less than 5% of its ground plane area for the modification needed to achieve the desired operational bandwidth. In the final part, the thesis presents a reconfigurable CIFA with the first ever tunable ground slot configuration in the literature. The novel tunable ground slot utilizes PIN diodes as a switching device to produce an antenna that is compact and covers the GSM, DCS, PCS and UMTS bands. The performance of all the designed antennas has been verified through experimental investigations. The obtained radiation characteristics for all the presented antennas are close to the omni-directional pattern, a feature which is needed for portable transceivers. Also, the achieved antenna gains and efficiencies are within the feasible range of 0 to 7 dBi that is suitable for most of the portable wireless applications. The presented novel antenna design methods provide potential solutions to the compact and multiband requirement of modern portable antenna designs. With the presented antenna design methods, the solutions to the compact and multiband requirement of modern portable antenna design are addressed.
Keyword Coplanar inverted-F antenna
Multiband antenna
Microstrip antenna
Ground slot
Return loss
Electrical switch
PIN diode
Additional Notes Color page: 29,38,41-43,45,52,55,65,75,77-82,86-92,94,102-107,116,118-119,123-131,140-147,154-156

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Created: Mon, 18 Jun 2012, 11:38:21 EST by Mr Ahmad Rashidy Razali on behalf of Library - Information Access Service