本論文係針對2.4GHz射頻辨識系統之近場天線來進行研究與設計，其中包含一款陣列天線與兩款手持式讀取器天線。首先，本論文提出一款近場能量集中之平面圓形微帶陣列天線，其乃由六個圓形微帶天線元素及一組具備適當相位輸出之饋入網路所組成，此設計方法與介質透鏡原理相似，使得近場區域的電場分佈能夠大幅提升，並且藉由電容性耦合方式來加以偵測陣列天線正上方的偶極天線標籤。另外，本論文亦分析多個標籤及陣列天線之間的耦合影響，由實驗結果顯示，所提出之陣列天線可於近場區域10公分以內，有效讀取12個均勻排列的電子標籤。
在手持式讀取器天線方面，第一款設計為近場應用之圓極化天線，有別於以往的圓極化天線設計，本論文觀察出方形截角微帶天線之近場電場強度會伴隨頻率變化而改變，並運用此特性來搭配後端模組之跳頻機制，以增加可讀取範圍。跟一般設計比較起來，本款圓極化近場天線不僅具備較強之電場強度，而且體積適中，故適合內建於手持式讀取器來辨識不同方位之標籤。其次，針對線性極化之應用，亦提出小型化讀取器平面型倒F天線(PIFA)，其設計架構係以傳統PIFA作為基礎，利用開槽式電容性耦合負載來大幅縮減天線體積。除此之外，為有效獲取標籤資訊，亦透過此款天線所具備之耦合特性來增加近場電場強度，進而提高整體辨識效率。

In this thesis, three kinds of near-field antennas for application in RFID 2.4GHz reader systems, which includes a microstrip array antenna and two patch antennas. To well focus the electrical field intensity in the near-zone, a patch array antenna based on the dielectric lens has been presented, which is implemented by using six circular patches and a feeding network. By properly designing the input phases of the feeding network for each element, the electrical field surrounding the near-field can be significantly enhanced for the array antenna, so that the dipole-like tags right above the array can be better detected by the capacitive coupling. The effects due to mutual coupling among the tags and the array antenna are thoroughly analyzed as well. Experimental results demonstrate that the proposed array antenna features fairly good performance for reading 12 tags within a range of 10cm at near-zone.
As to increase the read area for a handheld reader, on the other side, a rectangular patch antenna having circular polarization characteristic is therefore designed as an internal antenna. Here note that the electrical field intensity in the near-zone of the antenna varies against the frequency. Compared to other studies, the proposed design behaves stronger electrical fields to read the tags by using hopping frequency technology. Besides, a compact planar inverted-F antenna (PIFA) to possess linear polarization is also developed in this thesis, whose volume is well miniaturized using a slotted capacitive coupling loading. With such coupling property, the proposed PIFA can realize a stronger electrical field in the near-zone to enhance the identification performance of the RFID system.

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