1.5V 寬頻低失真通道選擇濾波器

Abstract

切換式電容濾波器的研究已經行之有年，在這方面的研究也相當的豐富。自從切換式電容濾波器首次被應用在脈衝編碼調變的系統上，許多相關於切換式電容濾波技術被快速的發展出來被應用到各種領域。隨著製程演進，切換式電容濾波器也逐漸被應用到高速的通信電路。對於SC的電路而言，動態範圍是評估電路效能的一個重要指標。較大的動態範圍可以使得SC電路有較高的位元數。而SC電路的動態範圍主要受到噪音和失真有兩個因素影響。許多關於噪音消除技術如chopper stabilized 和三角積分架構已經都被證實能有效地降低噪音功率。但是對於電路諧波失真的消除，依舊有著很大的改善空間。 此次研究主要在於使用TSMC 0.18μm的製程來設計一個高速低電壓低失真切換式電容濾波器。而設計低電壓的類比電路的主要目的是為了將類比電路和數位電路整合一起以減少面積成本。在低電壓的狀況下，以往傳統的類比電路架構都會遇到許多設計上的挑戰。信號的擺幅下降便是低電壓設計上的一大考驗，同時也會降低整個電路的效能。另外對於濾波器本身我們也希望能夠提升其線性度。因此經由許多架構上的考量以及關鍵元件的設計，可以有效的維持信號擺幅以及大幅的降低信號失真。同時我們也提出了一個低失真的取樣開關，將此應用在此次電路上藉以降低整個電路總諧波失真。

The research for switched capacitor filter has been developed for many years and plentiful. Since the first time the switched capacitor was applied on PCM system, many switched capacitor filtering technique were proposed and applied on various fields. With the process improvement, the switched capacitor filter is used in high speed communication circuit increasingly. The dynamic range is a key performance for the switched capacitor circuit. The switched capacitor circuit with the larger dynamic range has more bits. The dynamic range is mainly affected by the noise and the distortion in the switched capacitor circuit. A lot of solutions, like chopper stabilized and delta sigma architecture, for reducing the noise power were proved their effectiveness. But there is few for declining the distortion. We used the process, TSMC 0.18um, to design a high speed low voltage low distortion switched capacitor filter. The objective of low voltage analog circuit is for highly monolithic integration. But it makes the analog circuit more difficult. The signal swing would be reduced linearly by power supply. It would be affect the performance whole circuit. In addition, it is desired to raise the linearity of the filter. Through many design considerations and key component design, we can contribute the much less distortion. In the meanwhile, we proposed a novel low distortion MOS sampling switch applied on this filter for reducing THD.