生命體徵感測器所偵測的目標為人體的呼吸與心跳，這兩者的訊號強度相較於一般通訊所使用的訊號強度都還要微弱。由於室內為一密閉空間，因此訊號會受到牆壁反射，使得接收天線所接收到的訊號由於多重路徑的影響而降低其準確度。因此在設計應用於室內非接觸式生命體徵感測器時，除了需考慮到天線的效率以及增益外，也需要將天線的半功率波束寬做為設計天線的考量。在本論文中，我們將針對該環境設計一操作於2.45GHz且具窄波束寬的天線。
有別於一般傳統的槽孔與貼片天線，我們提出一接地面環繞的天線，該天線可同時激發槽孔與貼片模態，因此可藉由調整其物理尺寸來調整兩個模態的共振頻率，進而達成雙頻帶或寬頻共振。同時，由於電磁波碰到周圍所環繞的接地面時會形成建設性的反射波，使得天線的增益與波束寬能有較好的表現。並利用接地面環繞天線作為陣列天線的天線單元，再加入覆板的觀念來提升天線增益與減少天線的背向輻射。綜合上述所設計出來的陣列天線其最小波束寬在兩互相垂直平面分別達26與52度，增益為12.2 dBi。為了降低單一天線接收與發射訊號之間的干擾，因此在本論文中將發射與接收分成兩根天線，並針對兩根天線之間隔離度的問題作探討與改善。

Differences between indoor non-contact vital sign sensor and general sensors are “indoor” and “vital sign”. In indoor environment, receiving signals encounter multipath problem caused by the reflection of walls and furniture. Two main vital signs that we are concerned with are heartbeat and respiration; both of them are weaker than general signals used in communication. To overcome problems caused by multipath and weak signal strength, in this thesis, we design a narrow beamwidth antenna operating at 2.45 GHz for indoor non-contact vital sign sensor.
We propose a ground surrounded antenna (GSA) which differs from traditional slot and patch antenna. The proposed GSA excites slot mode and patch mode at the same time, so that we can achieve dual-bands or wide band by adjusting its physical parameters. Meanwhile, the reflected wave bounced back from the surrounding ground plane can cause constructive interference so that the antenna possesses better gain and beamwidth. Using GSA as the unit antenna of antenna array to achieve narrow beamwidth design, and adding the concept of superstrate can enhance antenna gain and reduce backlobe radiation. The minimum beamwidth at two orthogonal planes are 26 and 52 degrees respectively, and the antenna gain achieves 12.2 dBi. To reduce the interference between receiving and transmitting signals in single antenna, we use two separate antennas. Finally, we discuss and improve isolation problem between two antennas.

誌　謝 ii
摘　要 iii
Abstract iv
1. 序論 1
1.1研究背景與動機 1
1.2研究方法 8
1.3論文大綱 8
2. 接地面環繞天線設計 10
2.1接地面環繞天線介紹 10
2.2物理參數分析 13
2.3實作與量測探討 21
3. 陣列與覆板設計 23
3.1陣列天線理論 23
3.2陣列天線設計 25
3.3覆板應用的研究近況 28
3.4覆板設計 29
3.5具覆板之陣列天線設計 33
3.6實作與量測探討 35
4. GSA陣列天線隔離度探討 41
4.1 MIMO天線隔離方法概述 41
4.2 擺放位置對於隔離度的影響 42
4.3 實作與量測探討 47
5. 結論 50
參考文獻 51

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