臺灣博碩士論文加值系統

本論文主旨為可見光通訊之發光二極體光源分析及實現傳輸系統。將此技術應用在室內照明系統上，使原有的燈具不僅作為照明之用途，亦可發展為無線光通訊，並且傳輸速率在Mbit/s等級以上，達到室內照明應用之目的。而本實驗的發射端設計以直徑長55 mm之透鏡，增加光檢測器接收的光功率；並在接收端設計以直徑長30 mm之透鏡，優化其光檢測器的耦合效率；而光訊號經由光檢測器轉為電訊號後，設計串階運算放大電路將其電流訊號作放大，進而得到所需的訊號。其本論文架構是使用白光發光二極體作為通訊光源，由於白光發光二極體的混光技術是使用藍光發光二極體晶片激發黃色螢光粉之技術，故在通訊時隨著調變訊號速率提升，造成黃色螢光粉被激發的轉換速率不及藍光調變訊號之速率，經由實驗得到驗證其白光發光二極體傳輸速率被侷限在3 Mbit/s左右。由於白光發光二極體在傳輸上有頻寬受限的問題，所以改用單色光藍光取代白光發光二極體作為通訊光源，其原理是以前述白光發光二極體作為可見光通系統訊光源，但在接收器前加入藍光濾波器，使光檢測器接收單純的藍光訊號。經由實驗可得藍光發光二極體可見光通訊系統，在傳輸距離2.5 m時，其最高的傳輸速率為7 Mbit/s，接收光功率為-21.1 dBm。並且比較白光與藍光發光二極體之系統眼圖的實驗量測，觀察在相同傳輸速率2 Mbit/s時，其眼開度以藍光優於白光發光二極體之系統架構。而同時在系統中，加入直徑長55 mm之透鏡，使耦合效率優化0.8 V。由紅光、藍光、綠光發光二極體的光源進行傳輸實驗，得到藍光在最高的傳輸速率時，其光檢測器所接收之光功率較佳，由此證實紅光、藍光、綠光的發光二極體在室內光通訊中，以藍光發光二極體為光源首選。

In the thesis, LED plays a role in visible light communication as well as indoor lighting. The transmission speed could be upgraded to few Mbps per LED chip. In our experiment, the transmitter path is optimized by using a convergent focal lens with diameter of 55 mm, while the receiver may couple much LED power by using a divergent lens with focal length of 30 mm. In order to acquire sufficient signal power, operational amplifiers are used to improve the sensitivity of photodiode.
The white LED used in this experiment is based on mixed light technology using a blue LED chip with phosphor emitting yellow light, so that the white LED VLC could transmit only at about 3Mbit/s due to its low response time. To increase the LED bandwidth and improve the response time, a blue light LED may be obtained by putting a blue-color filter in front of the receivers to filter out the other colors of this white light LED. Thus, only the blue light spectrum is remained. In the experiment, the blue LED communication system at distance 2.5 m, its transmitted rates is up to 7 Mbit/s at a received power of -21.1 dBm. In the same modulation speed of 2Mbit/s, we compare the eye diagrams performance of white light LED with blue light LED and find that the latter one has better performance thanks to its broader bandwidth. A further 0.8 V amplitude is increased when a convergent lens with diameter of 55 mm is added in front of the receiver. These experiences confirm that the blue light LED has better performance than those LEDs of other wavelength ranges.

摘要 I
Abstract II
致謝 III
目錄 IV
圖表索引 VII
第一章 緒論 1
1.1 前言 1
1.2 研究動機與目的 2
1.3 論文架構 3
第二章 可見光通訊原理與技術 5
2.1 可見光無線通訊概念 5
2.2 發射端 7
2.2.1 發光原理 8
2.2.2 發光效率 9
2.2.3 白光技術 11
2.2.4 T型偏壓轉接器 14
2.3 傳輸通道 15
2.4 調變 16
2.5 接收端 17
第三章 光源特性分析與量測 20
3.1 LED光源 20
3.2 積分球儀器 21
3.3 光度學 23
3.3.1 光通量 23
3.3.2 1931 CIE-XYZ色度座標 24
3.3.3 相關色溫 26
3.3.4 演色性 27
3.4 實驗量測結果 28
3.4.1 白光LED之量測 28
3.4.2 藍光LED之量測 30
3.4.3 紅光LED之量測 32
3.4.4 綠光LED之量測 34
3.4.5 白光LED均勻光照明設計 36
3.4.6 量測小結 38
3.5 可見光通訊技術文獻探討 39
第四章 可見光通訊系統架構分析與量測 41
4.1 白光LED可見光通訊系統架構 41
4.2 藍光LED可見光通訊系統架構 46
4.3 LED可見光通訊系統之眼圖量測 50
4.4 紅、藍、綠各波長LED之可見光通訊系統 55
4.5 本章小結 57
第五章 結論與未來展望 58
5.1 結論 58
5.2 未來展望 59
參考文獻 60

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