應用於生醫訊號之可重組三角積分調變器設計

Abstract

由於生醫訊號具有訊號微弱及變化緩慢的特質，為求達到高解析度及低功率消耗，所以採用在這兩方面都有良好效果的三角積分調變器以符合應用所需。為了針對不同生醫訊號處理提供不同解析度的需求，本論文提出一個具可重組三角積分調變器。設計優點在於將三個調變器透過數位開關控制並使用重組的方式，達到高解析度的類比-數位訊號轉換。相較於一般因應不同解析度而增加元件設計的作法，更為節省晶片面積及提高轉換效率。可重組三角積分調變器具有兩種工作模式，一種分別為兩個一階架構，提供較低解析度，可減少轉換時間;另一種為前者重組而成的一個二階架構，可提供高解析度的訊號轉換。 本論文提出的可重組三角積分調變器設計採用台積電(TSMC) 0.35um 2P4M CMOS製程來實現，在取樣頻率256 KHz情形下，消耗功率為3 mW。對生裡訊號頻寬在1 KHz及超取樣率為128倍的情形下，一階SNR可達到66dB，二階SNR可達到86dB，分別具有十位元與十四位元的解析度。本論文的研究結果與不可重組的兩個一階及一個二階之傳統三角積分調變器面積相比，可節省30%晶片設計面積。

Due to low-amplitude and non-stationary properties of biomedical signals, high resolution and low-power consumption are necessary for the analog-to-digital (A/D) convector. Based on the above reason, the sigma-delta modulator (SDM) which has well performance in the resolution and power consumption is chosen. To deal with different biomedical signals and offering different resolution, this thesis proposes a reconfigurable sigma-delta modulator. The advantage of design is to use three built-in modulators to implement hardware reconfiguration and to achieve transformation of high resolution via digital switching control. Compared with the traditional method, the proposed design has higher efficiency and saves chip area. There are two kinds of operating modes. One is two first-order SDMs used to low resolution. The other is the second-order SDM which is reconfigured by two first-order SDMs, and it is suitable for higher resolution. The proposed sigma-delta modulator fabricated in TSMC 0.35um 2P 4M CMOS technology consumes 3 mW at 256 KHz. The SNR of the first-order and the second-order modulator can reach 66 dB and 86 dB, respectively, within 1 kHz of signal bandwidth and 128 times sampling rate. The resolutions are 10 bits and 14 bits with the respective to the first-order and the second-order modulator. Most importantly, the core area of the proposed one can be saved around 30% compared with area of two first-order and one second-order sigma-delta modulators without reconfigurability.