Book Description

This dissertation, "Compact Planar UWB Antennas for Wireless Device Applications" by Li, Liu, 劉荔, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: The thesis report presents the designs of compact planar ultra-wideband (UWB) antennas for wireless devices applications. Three main designs of UWB antennas are studied, namely, single UWB antennas, UWB multiple-input-multiple-out(MIMO)antennas, and transparent UWB antennas on the screens of mobile phones. For single UWB antennas, the designs of two compact planar monopole antennas with compact sizes of 2628 mm2and 3039.3mm2are presented. The UWB operations of the antennas are achieved using a ground slot under the feed line, offsetting the feed line and the radiator from the middle of the ground plane and smoothly transforming the feed line. Simulation and measurement show that the two antennas can achieve an ultra-wide bandwidth with approximately omnidirectional patterns. A deep notch-band in5.1-5.85 GHz is created in one of the UWB antennas by employing two pairs of meander lines (MLs), one pair being close to the feed line and the other pair along the upper edge of the ground plane. At the notch frequency, the simulated efficiency is only 4%. Three compact UWB-MIMO antennas with very compact sizes of 2640 〖mm〗 DEGREES2, 2138 〖mm〗 DEGREES2, and 2236 〖mm〗 DEGREES2 are designed. Each of them is designed using two UWB antenna elements perpendicularly or symmetrically placed. Different techniques such as using ground stubs besides the radiators, cutting inclined slots on the ground, and adding a T-shaped protruding from ground are proposed to lower mutual coupling between the two antenna elements. One of the antennas is designed to generate a notched band in 5.15-5.85 GHz using two ground strips. Simulation and measurement results show that these antennas can cover the entire UWB of 3.1-10.6GHz with mutual coupling of less than -15 dB, and envelope correlation coefficient of less than 0.1. An UWB antenna is designed using a transparent conductive film for applications on mobile phone screens. The effects of a finger touching the screen are studied. Results show that, with the radiator on the bottom side of the screen and a thin film with a thickness of 0.05 mm on the top side to separate the finger and the antenna, the effects of the finger can be minimized. In measurement of monopole antennas with small ground planes, due to the feeding cable used, there are always discrepancies between the simulated and measured results in radiation patterns, efficiencies, and gains at lower frequencies. To verify that the discrepancies in the results of these studies are indeed due to the feeding cable used in measurement, the models of the feeding cables are developed and used for simulation. Results show that, by using the cable model, the simulated and measured results in radiation patterns, efficiencies, and gains agree very well. DOI: 10.5353/th_b5334867 Subjects: Wireless communication systems - Equipment and supplies - Design and construction Ultra-wideband antennas