臺灣博碩士論文加值系統

表面聲波元件具有低損耗、尺寸小及頻率穩定度高的特性，且由於表面聲波元件對於溫度、壓力、表面粗糙度及表面電導率相當的敏感，表面聲波元件已被廣泛應用作為感測元件。利用表面聲波元件感測器的特性結合無線傳輸技術製作出的無線感測器，可使用於布線成本高或環境較惡劣的地方，而被動式的無線表面聲波感測器無須更換電池，可降低系統成本，且在完全封閉的工作環境下有較高的使用壽命。
無線式表面聲波元件主要由壓電基板、指叉電極與反射器所構成。本文首先以壓電晶體表面波的基本理論模型，使用數值方法計算非等向性材料的表面波波速，並選用鈮酸鋰128oY-cut作為壓電基板，鋁薄膜作為金屬電極材料，元件設計之操作頻率為433MHz，並在基板上設計不同型式之反射器，比較不同設計對反射回波訊號的影響，最後將反射器之基本特性應用在溫度感測器的設計上。
本研究設計三種不同反射器：開路金屬柵欄型式、短路金屬柵欄型及指叉電極型式，藉由網路分析儀取得頻率域下的反射損失，搭配離散傅立葉逆轉換，比較不同型式、不同尺寸設計下的時域反射損失。實驗結果顯示，開路金屬柵欄型式反射器與另外兩種型式相比，具有較高的反射係數，而反射器長度較長者具有較大之訊雜比；本研究並以實驗方法探討指叉電極型式反射器對外接阻抗變化之敏感度，實驗結果顯示指叉電極對數越多則對外接阻抗變化越敏感。
最後，本研究將指叉電極型式反射器結合負溫度係數熱敏電阻與光敏電阻，製作出溫度感測器及光熱複合感測器之原型。實驗結果顯示此種設計對溫度與光功率有極佳的感測能力，並提供光感測器良好的溫度補償。

In this thesis, 128o rotated Y-cut lithium niobate is used as piezoelectric substrate and aluminum film is used as metal electrodes in the SAW devices. The operating frequency of the SAW devices is designed in the range of 433MHz. To study the characteristics of reflectors in wireless SAW device, we design an one-port SAW device with three types of reflector, namely open circuit grating, short circuit grating, and IDT type. By using the network analyzer and the inverse discrete Fourier transform, the dynamic behavior of the SAW devices in time domain is presented.
In conclusion, the open circuit grating type reflector gives the highest return loss in time domain and the IDT type is the lowest one. The longer aperture of IDT and reflector has the lager SNR (signal-to-noise ratio) of the return loss in time domain. To study the characteristics of impedance-loaded IDT, the IDT type reflector was loaded with a variable resistor, and its return loss was measured. The experiment results show that the more pairs of IDT electrodes give the higher sensitivity to the resistance change.
Finally, we combined our SAW device with the NTC (negative coefficient of temperature) thermistor and photoresistor as impedance-loaded SAW sensors. Experimental results show that our designs have good sensitivity as temperature sensor and photo sensor with temperature compensation.

摘要 I
ABSTRACT III
目錄 V
圖目錄 VIII
表目錄 XIV
第一章 緒論 1
1.1 研究動機 1
1.2 文獻回顧 2
1.3 本文簡介 3
第二章 表面波波速及表面聲波元件之理論分析 5
2.1 壓電晶體表面波波速計算 5
2.1.1 壓電效應 5
2.1.2 統御方程式 5
2.1.3 邊界條件 6
2.1.3 數值方法計算表面波波速 7
2.2 表面聲波元件基本原理 10
2.2.1無線表面聲波元件 10
2.2.2脈衝函數模型(Tancrell and Holland,1971) 10
2.3 表面聲波元件之重要影響參數 12
第三章 表面聲波元件設計及微機電製程 19
3.1 表面聲波元件設計 19
3.1.1 壓電基板選擇 19
3.1.2 指叉電極與反射器之設計 19
3.2 微機電製程 20
3.2.1 晶圓清洗 20
3.2.2 金屬濺鍍 20
3.2.3 黃光製程 21
3.2.4 蝕刻電極 22
3.2.5 晶圓切割與封裝 22
第四章 表面聲波元件之特性量測與比較 33
4.1 量測系統架構 33
4.1.1 網路分析儀 33
4.1.2 離散傅立葉逆轉換 34
4.2 不同反射器設計對頻率響應及時域訊號之影響 35
4.2.1 延遲時間 35
4.2.2 開路金屬柵欄型式反射器之元件特性 36
4.2.3 短路金屬柵欄型式反射器之元件特性 36
4.2.4 交指叉電極型式反射器之元件特性 37
4.2.5 不同反射器型式對頻率響應及時域反射訊號之影響 38
4.2.6 元件時域響應中的第四反射訊號 38
4.3 指叉電極型式反射器外接阻抗對時域訊號之影響 39
4.4 總結 40
第五章 無線感測器之應用 133
5.1 延遲時間的變化於溫度感測器之應用 133
5.1.1 實驗原理 133
5.1.2 實驗系統架構 133
5.1.3 實驗結果 134
5.2 外接熱敏電阻之溫度感測器 134
5.2.1 熱敏電阻 134
5.2.2 量測系統架構 135
5.2.3 實驗結果 135
5.3 光、熱複合式感測器 136
5.3.1 光敏電阻 136
5.3.2 量測系統架構 136
5.3.3 實驗結果 137
5.4 結論 137
第六章 結論與未來展望 153
6.1 結論 153
6.2 未來展望 154
參考文獻 156

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