以0.18微米互補式金氧半製程實現高精確度且低損耗之差動饋入數位衰減器

Abstract

本論文以0.18微米互補式金氧半製程來設計並實現應用於700 MHz 以及70 MHz差分信號系統中的高精確度且低損耗之數位衰減器。論文最主要的貢獻在於提出一種有別於現今普遍的衰減器電路架構，此架構可消除切換衰減狀態時所造成的級間阻抗變化之影響，提高不同衰減位元間的隔離度，進而提升各階衰減量之精確度，同時也可把一般衰減器中常見的高介入損耗改善到幾乎為零。本論文所設計完成工作於70 MHz的原型電路，其衰減量精確度能夠達到0.015 dB以內(最高衰減量為71.25 dB)，700 MHz原型電路則可達到0.2 dB以內(最高衰減量為45 dB)。

This thesis presents the design and implementation of differential-feed digital attenuators with high accuracy and low insertion loss using TSMC 0.18-m CMOS process for operation at the 700- and 70-MHz bands, respectively. The main contribution of this thesis lies in the proposal of a novel attenuator topology different from conventional ones. With this new topology, the influence of inter-stage, or inter-bit, impedance variation during ON/OFF switching state can be eliminated. It not only provides high isolation between adjacent attenuation bit but also helps reduce the insertion loss due to the inter-stage matching circuit that would otherwise be used. Importantly, the attenuation accuracy is significantly improved thanks to the excellent inter-bit isolation. The insertion loss can be almost 0 dB. The attenuation accuracy of the 70-MHz prototype circuit is within 0.015 dB (the maximum attenuation level is 71.25 dB). Meanwhile, for the 700-MHz prototype circuit, the attenuation accuracy is within 0.2 dB (the maximum attenuation level is 45 dB).