| Summary: | 碩士 === 逢甲大學 === 電機工程所 === 99 === In this thesis, the designs of multiband antennas for wireless communication system are studied. Here, three different antennas structure for mobile application are investigated and discussed. A hybrid mobile device antenna with double-layer structure for multiband operation is initially proposed. It is able to cover the wireless applications such as GSM/DCS/DCS/UMTS/WLAN 2400. The main structure of this antenna is composed of two layers; the top layer of proposed antenna produces three resonance modes (at around 0.88, 0.97 and 1.18 GHz) with respect to three radiation strips. The bottom layer of proposed antenna produces three resonance modes (at around 1.38, 1.76 and 2.45 GHz) by embedding a T-shape open-ended slot into the rectangle radiation patch. The second proposed antenna is a compact size (15 mm × 40 mm) microstrip-fed printed planar inverted-F antenna (PIFA) for mobile applications. The main structure of this antenna is a simple double-folded PIFA with two wide open-ended radiating sections. By tuning the two wide open-ended radiating sections, optimum impedance matching and inclusion of UMTS band can be achieved. Compared to the previously proposed antenna, this antenna has the advantages such as planar structure, and additional operating band in the WLAN 5.2/5.8 and WiMAX. Finally, a coplanar printed antenna with inverted L-shape coupling feed is proposed. By using an inverted L-shape coupling feed and a meandered shorting strip, two wide operation bands are excited. Both the lower and upper operation band can cover LTE 700/GSM and DCS 1800/PCS 1900/UMTS/LTE 2300, respectively. To operate at LTE 2500 band, a technique of joining a parasitic stub around the feed point which excites a resonance mode at 2.72 GHz is introduced. This proposed antenna can be used as a multiband antenna operation for the application in fourth generation (4 G) wireless communication system. By comparing to the other wireless communication system, the 4G wireless system can provide faster transmission speed and more system capacity.
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