USP Theses Collection


close this section of the library Lal, Jayshree.

View the PDF document Compact antennas for mobile communications
Author:Lal, Jayshree.
Institution: University of the South Pacific.
Award: M.Sc.
Date: 2006.
Call No.: pac In Process
BRN: 1033133
Copyright:10-20% of this thesis may be copied without the authors written permission

Abstract: Size miniaturization of microstrip patch antennas is one of those antenna research fields, which is becoming essential in many practical applications. The demand for smaller mobile handsets, cordless phones, global position satellites and other next – generation wireless terminals has placed a huge responsibility on the communication engineers to design and develop compact antennas such that the size of the mobile terminals can be reduced as well.The objective of this thesis is to investigate small patch antennas suitable for mobile communications. There are currently many size reduction techniques available in the open literature. In this research, some of those techniques were explored to determine the best ways of reducing the antenna real estate. Consequently, a compact Y-shaped stacked antenna was designed. This antenna is easy to manufacture and could be used in mobile terminals. Using the techniques explored in the open literature, another compact printed antenna was then designed. It is F-shaped and has a foam material sandwiched between the ground plane and the radiator plane to improve its bandwidth performance. This antenna could be used for PCS applications. An interleaved F-shaped and cross- shaped stacked antenna was then designed using the technique of shorting pins and slots. This compact design could find applications in systems such as DCS 1800 (1805 MHz- 1880 MHz), Digital European Cordless Telephone (1880 MHz-1990 MHz), Personal Handy Phone System (1895 MHz-1918 MHz) and PCS systems. The fourth compact stacked antenna configuration was designed using the common size reduction techniques such as slots and shorting pins. The antenna uses a square shaped print for the top layer and has a cross-shaped bottom layer. The top radiator uses semi circular grooves to maximize current path such that miniaturization is achieved. Finally, we have used the patch configuration from the first two antennas to design a final Y-shaped and interleaved F-shaped stacked antenna. The antenna has a simple configuration due to the position of the shorting pins and the probe pin. Chapter 4 of this dissertation deals with the simulation results of the antennas designed above. The impedance bandwidth of each antenna is determined and the percentage size reduction is calculated compared to a conventional microstrip patch antenna (reference antenna). The radiation patterns of these antennas are also studied. The Y-shaped stacked antenna has a bandwidth of 10.2 %. The antenna real estate decreased by a factor of 3 compared to the conventional patch antenna. A simulated bandwidth of (VSWR >2) 7 % was achieved for the interleaved F-shaped antenna. The antenna is 65 % smaller than the reference antenna. To validate the designs using the IE3D simulator software, the interleaved F-shaped antenna was fabricated and tested. The return loss bandwidths of the simulated and measured results (VSWR >3) are in good agreement with each other in the L band of the frequency spectrum. However, degradation below the –5 dB return loss results can be attributed to fabrication tolerances when manufacturing the antenna. An impedance bandwidth of 10.5 % was achieved for the stacked interleaved F-shaped and cross- shaped antenna. This is a relatively high bandwidth. The antenna real estate decreased by 65 %. The fourth design has a bandwidth of 8.4 % and is again 65 % smaller than the reference antenna. In the case of the last design, a 63% patch size reduction from the conventional probe fed rectangular patch antenna has been observed whilst the simulated antenna bandwidth is 8.15 %.
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