本論文提出一個結合阻抗感測器的前端讀取電路來量測尿液中肌酸酐的濃度，可應用於腎臟與尿道的診斷與預防感染。由於不同濃度的肌酸酐會造成感測器的阻抗變化，利用前端電路讀取阻抗變化值後，經由連續趨近式類比數位轉換器進行數位訊號轉換，得到的數位值透過演算法進行數位碼轉阻抗的數學公式可計算出阻抗值，完成阻抗分析。
交流電化學阻抗頻譜法是一種分析感測器傳導與介電特性的方法之一，已成為近幾年來阻抗頻譜法的主流。原理是透過不同頻率(譬如1mHz~1MHz)的弦波刺激訊號經由介面電路傳於感測器上，並分析其中的響應結果。本論文的目標是將交流電化學阻抗頻譜法的電路簡化，電路設計包含下面三個部分：(1)感測器介面電路；(2)連續趨進式類比數位轉換器的晶片設計；(3)量測上的整流電路設計。在實際操作上我們先將介面電路與感測器結合，並輸入一個100Hz的弦波刺激訊號於介面電路，此訊號會透過介面電路在感測器上提供一個電流迴路，並產生電位的變化，進而得到感測器本身的阻抗值。介面電路輸出訊號會因為感測器的阻抗變化(Z∠θ)，Z與θ分別為阻抗振幅與相位，而本論文著重於分析感測器阻抗值的振幅。
該振幅信號可經由介面與整流電路轉換成為一個穩定的直流，再經過連續趨近式類比數位轉換器取出阻抗振幅參數的數位值，經換算之後可得到感測器在不同肌酸酐濃度下的阻抗值，再利用變化量製作檢量線，求出肌酸酐的濃度數值。
實現上我們則採用TSMC 0.18μm CMOS製程，晶片內部包含阻抗式感測器介面電路與連續趨近式類比數位轉換器，而全波整流電路則為外部電路。在取樣頻率為31.25kHz的條件下，連續趨近式類比數位轉換器量測到的SNDR為65.5dB、有效位元(ENOB)為10.59 bits，晶片面積為1.743 1.153mm^2(含IO PAD)整體功耗為3.19762mW晶片功耗與整流電路功耗分別為199.62μW與2.998mW，阻抗量測的線性度為0.9999。為了濾除PCB上的雜訊，在系統中加入四個低通濾波器，再經由電壓位準提升電路將訊號範圍放大，由於電路本身的非理想因素，線性度變為0.9997。本設計在線性度的量測上有不錯的表現，因此適合阻抗量測技術的使用與尿道和腎臟病變的診斷。

This thesis proposes an integrated circuit design, which combines an impedance sensor and front-end readout circuit with Successive Approximation Analog-to-Digital Converter (SAR ADC), to efficiently measure urine Creatinine concentration (CC). The Creatinine concentration is a key index for diagnosis and can be used to prevent kidney disease and urethral infection. Due to different CC causing the variation of sensor’s impedance, we can convert the result into digitally quantized code by using the proposed front-end circuit with SAR ADC. Therefore, the impedance value can be calculated and analyzed via a simple formula transformation.
Electrochemical Impedance Spectroscopy (EIS) is one of the methods for measuring dielectric and transport properties of materials. It has become the standard in recent years. This method is realized by sending some stimulating sine wave signals into interface circuit. These signals have different frequencies (eg. 1mHz~1MHz), and we can collect their frequency responses from the sensor output and analyze the results. The main purpose in this theise is to simplify the EIS circuit which contains three blocks：(1) Sensor interface circuit; (2) SAR ADC chip design and (3) Rectifier circuit design in the measurement board. In operation, the sensor and the interface are combined together. And a 100 Hz stimulating sinusoid signal is required to provide a current loop in sensor leading voltage variation, and then we can obtain the sensor impedance value. The sensor impedance (Z∠θ) can be estimated from the variation of output signal, where Z and θ, respectively, represent the impedance amplitude and phase. In this thesis, we only focus on the amplitude of impedance.
The analog signal after the interface and full wave rectifier is converted to a DC signal. Through the SAR ADC, the impedance amplitude will be translated in a digital form. Then, we can calculate the impedance to make sure the reflection of Creatinine concentration. After describing calibration curve in impedance variation, the Creatinine concentration can be acquired.
The proposed design is implemented in TSMC 0.18μm CMOS process, the chip includes impedance sensor interface circuit and SAR ADC. However, full wave rectifier is off chip. Under the condition of 31.25-KHz sampling rate, the SAR ADC measurement results show that the SNDR is 65.5dB and ENOB is 10.59bits. The chip area is 1.743×1.153mm^2(including IO PAD). The total power consumption is 3.19762mW where the chip power consumption is 199.62μW and the rectifier power consumption is 2.998mW. Impedance measurement linearity is 0.9999. Since four low-pass filters are added in the system for removing the PCB noise, the new linearity becomes 0.9997 which is still good for apllication. In conclusion, the the proposed design is vary suitable for the diagnosis of kidney diseases and urinary tract infection.

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