許多植入式生物微系統被廣泛的應用在神經義肢與相關的臨床研究上。對於一個植入式生物微系統而言，電源是設計上最主要的考量。由於使用壽限的問題，電池在植入式系統應用中不是最佳的選擇。近年來，植入式生物微系統的設計是利用電磁耦合方式，將電源與資料以無線傳輸方式耦合到系統內，以提供系統正常操作所需。另一方面，具生理訊號擷取與傳送的雙向傳輸功能也是此領域的發展的重點。本研究目的是以超大型積體電路（VLSI）之設計概念，驗證具有無線雙向傳輸功能的生物微系統之體內單元電路，並呈現所有的電路模擬結果。
整個植入式系統包含內部射頻前端電路、控制電路、刺激器以及資料傳送電路。電路操作是由體內電路接收一個包含電源及數位資料、且由外部發射的2MHz振幅調變訊號。此訊號經由內部電壓整流與穩壓電路產生一個穩定的直流電壓以提供整個內部系統應用，同時數位資料也經由解調器萃取以執行神經肌肉電刺激。此外，系統也將擷取生理訊號以做為資料傳輸應用。本研究使用Hspice電路模擬軟體，並依據台積電(TSMC) 0.25um CMOS製程之電路設計規則來驗證整個植入式系統的功能性區塊。模擬結果顯示RF前端電路能提供一個穩定的2.5V 直流電壓輸出，並且準確的解調出數位資料。同時訊號處理電路部分，前置放大器能提供生理訊號穩定的放大倍率（40~60 dB）。濾波器電路採用ladder type之架構，設計一頻帶為250Hz到5KHZ之帶通濾波器，模擬結果顯示其適合應用於生理訊號的處理。最後，A/D轉換器為一個8-bit解析度SAR(successive approximation register)架構的A/D轉換器，模擬結果也顯示其能提供一正確的類比/數位資料轉換。而本研究的所有電路模擬結果也將做為未來發展植入式生物微系統的基礎。

Various implantable bio-microsystems have been designed for the neural prostheses and other clinical studies. For the implantable bio-microsystem, power is one of the major concerns in the system design. Due to the lifetime limitation, battery is not the optimal choice in the implanted devices. In recent years, electromagnetic propagation through inductive coupling links has been commonly used to deliver power and information into these implantable bio-microssytems. Another issue is the outward transmission of sensing data, which requires an internal data transmission system with the power acquired from the external controller. The aim of this study is to investigate the functional blocks needed for a wireless bi-directional transmission micro-stimulator and present their simulation results.
This implantable device includes internal RF front-end circuit, control circuit, stimulator, and on-chip transmitter. The operation of this system is to receive an AM modulated 2MHz signal generated by external circuits. This signal includes the power and data necessary for the whole internal circuits. Through the internal circuits, a stable DC voltage and digital data can be extracted for neuromuscular stimulation. Besides, the system can acquire the biological sensing signal for on-chip transmission.
In this study, most of the functional blocks for the implantable device can be verified by using Hspice according to the design rules of TSMC 0.25 um CMOS process. Our simulating results show that the RF front-end circuits can provide a stable 2.5V DC voltage and extract digital data accurately. Meanwhile, in the signal process circuits, the preamplifier can provide a stable gain for bio-signals (about 40dB to 60dB). The bandpass filter with bandwidth between 250Hz to 5KHz filter circuit is designed with ladder type approach. Finally, an accurate A/D data converter with 8-bitresoultion of successive approximation register (SAR) has been verified too. All the simulating results can be a base for future fabrication of implantable devices.

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