本論文的目的是利用頻率選擇面增加對數週期天線(Log-periodic antenna)的增益值，此天線具無線區域網路(WLAN)雙頻操作特性。首先設計對數週期天線，對天線參數做最佳化，使得反回損失(Return loss)在我們所要達到的頻段內都符合需求的10dB。其次，設計具有週期性結構的頻率選擇面，藉此提高增益。由實驗結果顯示，對2.45 GHz頻段而言，未加頻率選擇面時，天線增益為4.30 dBi，加上頻率選擇面後，增益提升至12.27 dBi。再者，對5.5 GHz頻段，未加頻率選擇面時，天線增益為3.93 dBi，加上頻率選擇面後，增益提升至11.6 dBi。

The purpose of this paper is to increase the antenna gain of a log-periodic antenna by introducing a frequency selective surface (FSS). The proposed antenna can operate in wireless local area network (WLAN) with dual-band operation at 2.45 GHz and 5.5 GHz. First, the log-periodic antenna is designed and optimized by HFSS. Second, an FSS is introduced to increase the antenna gain without the sacrifice of impedance bandwith. The experimental results show that for the band of 2.45 GHz, the antenna gain is 4.30 dBi without FSS and 12.27 dBi with FSS. Moreover, for the band of 5.5 GHz, the introducing of the FSS increase the antenna gain from 3.93 dBi to 11.6 dBi.