適用於無線區域網路應用之CMOS低雜訊放大器設計

Abstract

人們之間的溝通模式由於無線通訊科技的便利而有巨大的改變。除了手機之外，近年來無線資料傳輸模式亦引起相當的注意。在無線通訊系統內，接收端的設計中，低雜訊放大器(LNA)在訊號接受路徑上扮演相當重要的角色，它提供足夠的訊號強度，將電路中的雜訊降到最低以維持訊號的品質。在本論文中，以互補式金氧半導體之0.18微米製程(CMOS 0.18µm process)製作低功率及雙頻帶的低雜訊放大器。 首先被提及的低雜訊放大器具有低電壓與低功率操作的功能。本論文採用了電流共用架構，將二個共源放大器(common-source)串疊而成，在低電流功率消耗下得以達到高的小信號增益。全積體化的5.7GHz低雜訊放大器，以維持良好的輸入及輸出阻抗匹配為前提下，提供16.4dB的增益、3.5dB的雜訊指數與8dB的可變增益範圍。在1volt的電壓操作下，全積體化的5.7GHz低雜訊放大器消耗3.2mW，而小信號增益與消耗功率之比值為5.12 dB/mW。 其次，以使用最小的硬體為前提，本論文設計的低雜訊放大器具有雙頻帶的功能。藉由切換直流偏壓與電晶體大小，使不同頻帶下的輸入阻抗得以匹配；在輸出阻抗部分，則採取切換式電容來達成。我們成功地運用新匹配技術，實作全積體化CMOS 0.18μm 2.4-GHz/5.2-GHz 雙頻帶低雜訊放大器：當操作在2.4-GHz頻帶下，其增益為10.1dB，雜訊指數為2.9dB；而在5.2-GHz頻帶下，其增益為10.9dB，雜訊指數為3.7 dB。不需要任何其他外加匹配元件，在二個頻帶下維持著良好的輸入及輸出匹配(皆在-10dB以下)。

The convenience introduced by the wireless technology has drastically changed the way people communicate. Other than cellular phone services, the wireless data communication has attracted great attention in recent years. In the transceiver design of a wireless LAN system, the low-power amplifier (LNA) plays an important role in the signal receiving path. It is required to provide sufficient signal amplification while maintaining a minimum noise to ensure the quality of the received signal. In this thesis, LNAs are designed and fabricated in a standard 0.18-μm CMOS technology for low-power and dual-band applications. The first CMOS LNA demonstrated is focused on its low-power and low-voltage operation. With a current-reused topology, the common-source gain stages are stacked for minimum power dissipation while achieving high small-signal gain. The fully integrated 5.7-GHz LNA exhibits 16.4-dB gain, 3.5-dB noise figure and 8-dB gain tuning range with good input and output return losses. The LNA consumes 3.2-mW dc power from a supply voltage of 1 volt. A gain/power quotient of 5.12 dB/mW is achieved in this work. Another LNA is designed to achieve dual-band operations with minimum hardware overhead. By switching the size and dc bias current of the input transistor, good input matching can be achieved. In addition, switched capacitors are used for the output matching at both frequency bands. Using the proposed design technique, a fully integrated 2.4-GHz/5.2-GHz dual-band LNA is presented. The fabricated LNA exhibits 10.1-dB gain and 2.9-dB noise figure at 2.4-GHz band, and 10.9-dB gain and 3.7-dB noise figure at 5.2-GHz band. Input and output return losses better than 10 dB are achieved at both frequency bands without external machining components.