電阻抗斷層造影(Electrical impedance tomography, EIT) 為一種應用於藉由人體組織有不同的導電率，量測其橫切面阻抗變化之系統，但重建出的影像受到其解析度的限制，且易受雜訊影響，影響量測訊號準確性，重建後影像不夠精確。本論文嘗試建立一套具可調頻率及相位之正弦波信號源之EIT多頻電流源之數位及類比解調平台，由電腦控制直接數位合成(Direct Digital Synthesis，DDS) 產生可由DDS直接控制之頻率1kHz~100kHz之正弦波做為參考與解調端之信號源，以及藉由類比數位轉換(Digital to Analog Converter, DAC)控制電流大小。由設計電壓控制電流源(Voltage Control Current Source，VCCS)，產生穩定之電流源，經過待測物後實現數位及類比解調平台，比較其差異性，並討論兩者之可行性，藉此做為日後選擇設計EIT系統時之參考。直接數位合成(Direct Digital Synthesis, DDS)電路輸出，頻率在1kHz到100kHz，總諧波失真(Total Harmonic Distortion, THD)平均為0.57%，而在電壓控制電流源(Voltage Control Current Source，VCCS)輸出，頻率由1kHz到100kHz，THD平均為0.91%。使用AD630晶片實現類比解調，實際量測純電阻並使用HIOKI 3532-50 LCR Meter量測真實電阻作驗證，頻率100kHz相關係數r2=0.9832，在量測電阻與電容並聯等效時，頻率10kHz，電阻為510Ω，電容由1nF到0.47μF，與LCR meter實際量測值之相關係數r2=0.8281。而以DSP實現數位解調量測純電阻時，頻率100kHz時與實際量測電阻之相關係數r2=0.9988，且而在量測電阻與電容並聯等效時，頻率100kHz，改變電阻由100Ω~510Ω，電容由1nF到0.47μF，與LCR meter實際量測值之相關係數從r2=0.9849到r2=0.9992。

Electrical Impedance Tomography (EIT) is an application specifically designed to measure the impedance variation in human tissue. The accuracy of the signal acquired depends on the resolution limit. The aim of this paper is to establish an EIT system that contains a Direct Digital Synthesis (DDS), with PC controlled MCU that can vary the frequency and phase of a voltage signal by changing the control word of the current source, and a Digital to Analog Converter (DAC) was used to change the signals amplitude. Since we only need current, a Voltage-Controlled Current Source (VCCS) was added for the current conversion. The DDS circuit produced frequencies having values of 1 kHz and 100 kHz, Total Harmonic Distortion (THD) ranging from 0.5% to 0.66%. Post measurement in the VCCS showed a 0.81% and 1.10% increase in THD. The AD630 chip was used for analog demodulation. To acquire the actual measurement of the pure resistance a HIOKI 3532-50 LCR Meter is used. A system with a 100 kHz frequency, wherein the impedance is equal to its resistance and capacitance, a correlation coefficient r2 of 0.9832 was acquired. And for a system having a different frequency of 10 kHz, equivalent resistance of 510Ω and a capacitance range of 1nF to 0.47μF, the r2 acquired is 0.8281. Last part of the system is the DSP for digital demodulation measurement. For a frequency of 100 kHz, real resistance, the actual measurement of the r2 is 0.9988. For a 100 kHz running system, change in resistance is from 100Ω up to 500Ω, capacitance from 1nF to 0.47μF, the actual measured values of the r2 is from 0.9849 up to 0.9992.

摘 要 I
ABSTRACT II
致 謝 III
目 錄 IV
圖目錄 VIII
表目錄 XII
第一章 緒論 1
1-1 緒論 1
1-2生物組織之電氣特性 2
1-3 文獻回顧 5
1-4 研究動機及目的 13
1-5 論文架構 14
第二章 材料與方法 15
2-1 系統硬體架構 15
2-2 硬體設計 17
2-2-1 DDS晶片介紹 17
2-2-2 數位轉類比(DAC) 21
2-2-3 電壓控制電流源(VCCS) 24
2-2-4 儀表放大器 25
2-2-5 可程式增益控制放大(PGA) 25
2-2-6 自動放大增益控制(AGC) 26
2-2-7 同步解調 27
2-2-7-1 開關解調 27
2-2-7-2 乘法解調 30
2-2-7-3 數位解調原理 32
2-2-8 信號品質量測 33
2-2-9 DSP簡介 34
2-3 軟體設計 36
2-3-1 TMS320F28335記憶體配置 36
2-3-2 ADC自動輪序轉換運作原理 38
2-3-3 ADC模組的時脈預除器 39
2-3-4 DSP實現數位解調 41
2-3-5 USB轉並列埠傳輸 43
第三章 結果與討論 44
3-1 DDS實際量測實驗 44
3-2 AD630解調實驗 47
3-3 DSP數位解調實驗 49
3-3-1 DSP數位解調平台 49
3-3-2 DSP ADC轉換特性實驗 52
3-3-3 DSP 解調前ADC取樣 53
3-3-4 DSP 之ADC取樣點位移實際量測 54
3-4 實際阻抗量測 57
3-4-1 AD630類比解調量測電阻實驗 57
3-4-2 AD630類比解調測量電阻與電容並聯實驗 58
3-4-3 DSP數位解調量測電阻實驗 62
3-4-4 DSP數位解調量測電阻與電容並聯實驗 63
3-4-5 DSP數位解調實際量測相位實驗 69
3-4-6 系統測試 70
3-4-7 影像重建結果 73
第四章 結論與未來展望 77
4-1 結論 77
4-2 未來展望 78
參考文獻 79

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