超寬頻無線網路應用之低功率互補金氧半射頻前端發射器設計

Abstract

本論文針對超寬頻(UWB)無線網路應用提出低功率互補式金氧半(CMOS)射頻前端發射器之設計。本文提出之前級放大器(Pre-Amplifier)採用低功率電流共用散佈並接放大器架構，使PMOS與NMOS電晶體偏壓於相同直流電流，以達成低功耗和超寬頻之設計目標。經由0.18-µm CMOS 製程進行電路實作，量測出1-7.9GHz的超大頻寬與15mW的極低功耗，同時具有7.3dB的最大功率增益、2dBm的最大輸出功率，驗證此低功率電流共用散佈並接放大器架構之優點。將此優異放大器架構應用於超寬頻射頻前端發射器，再利用回授電阻固定輸出電壓，以保持其優異特性，加上被動式混波器，以符合低功耗與高頻寬之要求。封裝量測結果顯示，超寬頻的前端發射器在3-8.3 GHz 可獲得平均功率轉換增益-12dB 有著±2dB變動，同時在LO 頻率3.4GHz的測試下有著0dBm的最大輸出功率。此超寬頻射頻前端發射器參考多頻帶正交頻率多重分割技術規格草案的第一、二、三頻帶組需求，運作頻帶從3GHz到8.3GHz，並以射頻/基頻共同模擬來驗證其高增益以及良好線性度之特性。

This thesis presents a low-power design of a direct conversion CMOS RF transmitter front-end for ultra-wideband (UWB) wireless applications. To achieve low power consumption and wide operating bandwidth, the proposed Pre-amplifier employing low power dc feedback current reuse distributed amplifier which the dc current flows through the PMOS to NMOS transistors to reuse the same bias current. A circuit implementation in 0.18-μm CMOS process shows a 1-7.9GHz bandwidth. The amplifier provides a maximum forward gain (S21) of 7.3dB while drawing 15 mW from a 1.6V supply. The maximum output power of 2dBm has been measured. In this thesis, design optimization for the low power current reuse distributed amplifier in wide bandwidth applications is also presented. The novel topology of current reuse distributed amplifier is applied to the RF front-end design for the UWB direct conversion transmitter and uses the feedback resistance to fix the output dc voltage in order to maintain excellent performance. In the RF front-end, a wideband passive mixer is designed for the purpose of low power, and high bandwidth before the Pre-amplifier. The measurement results exhibit that the UWB direct conversion transmitter of package version achieves conversion gain of -12dB from 3-8.3GHz with ±2 dB variation, and obtain the maximum output power of 0dBm at LO frequency 3.4GHz. The UWB transmitter front-end referenced to the band group #1, 2 and 3 of the Multi-Band OFDM with operation frequency range 3-8.3 GHz demonstrates low power, high gain, and wide bandwidth. It is also verified by a RF/Baseband co-simulation.