| Summary: | 碩士 === 國立交通大學 === 電信工程研究所 === 98 === The demand for compact internal WWAN (Wireless Wide Area Network) antenna embedded in the laptop computer for penta-band operation has seen growing attention. For laptop computer applications, the width of the antenna is limited to the overall width of the edge of laptop computers, which results in narrow and low profile needs. However, when the antenna is very close to the ground plane, it is bound to reduce the antenna efficiency. To solve this problem, the EBG structure is applied to the ground plane, which behaves as a high impedance surface at the resonance frequency of the EBG structure. Thus, the antenna can placed close to the ground plane while maintaining the antenna performance.
The new 1-D EBG structure is proposed in this thesis. Unlike the conventional EBG structures, the proposed 1-D EBG structure utilizes a printed parallel LC circuit, which is more compact and easy to fabricate. According to the advantages shown above, two antenna applications base on the 1-D EBG structure are presented. Both of them are fabricated on low cost FR4 substrate of 0.4 mm. First, a high efficiency ground-proximity dipole antenna using 1-D EBG structure is designed. The distance between antenna and the ground plane is only 10 mm with the overall size of 10 mm × 163 mm. The good radiation properties are obtained with the measured radiation efficiency over 55.6% for GSM (824 MHz-960 MHz) applications.
Secondly, the penta-band (GSM850/900/1800/1900/UMTS) ground-proximity printed penta-band monopole antenna is achieved with different 1-D EBG structures combined together. These 1-D EBG structures are combined to provide wider EBG operation bandwidth for GSM (824 MHz-960 MHz), so the monopole antenna and ground plane can be placed in close proximity without affecting the antenna performance in the lower band. In the higher band (1710 MHz-2170 MHz), the 1-D EBG structures can be viewed as efficient radiators, which create additional two resonances and penta-band is thus achieved. Compared to the previous design, the second antenna has a smaller size of 10 mm × 63 mm. The radiation performance is still maintained, which is all above 51.5% in penta-band. Given the design flexibilities and compactness, the antenna designed with 1-D EBG structures is feasible to commercial applications.
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