具有高動態範圍之CMOS極座標發射機

Abstract

本論文提出一種改良式的高動態範圍脈衝調變極座標發射機架構。在數位脈衝調變器的前級加入輔助的數位增益/衰減方塊，可以有效降低系統的硬體複雜度與成本。本論文提出之架構不同於傳統的脈衝調變極座標發射機架構，透過數位增益/衰減方塊的輔助，不需要採用高動態範圍的可變增益放大器就可以實現一個具有高動態範圍的發射機。 為了驗證所提出之系統架構的可行性，使用TSMC 0.18μm 1P6M Mixed Signal CMOS製程實現射頻脈衝產生器晶片，結合商用的功率放大器模組進行驗證。量測結果顯示，改良式的高動態範圍脈衝調變極座標發射機架構只需要採用一個具有21 dB動態範圍的可變增益放大器即可通過需要80 dB高動態範圍的CDMA2000規範。測量的結果也顯示，在包絡信號與相位信號路徑上的數位類比轉換器僅僅需要8位元的解析度就可以通過CDMA2000的相鄰通道功率比(ACPR1)與相間通道功率比(ACPR2)規範。相對於使用線性功率放大器實現之傳統發射機架構，本論文提出的架構具有低成本、高效率之特性，更適合發展於無線行動通信系統當中。

In this thesis, an improved pulse-modulated polar transmitter for wide dynamic range applications is presented. The utilization of an auxiliary digital gain/attenuation block in front of the digital pulse-width modulation (DPWM) block is proposed to improve the performance and cost of the conventional pulse-modulated polar transmitter. With proper digital gain/attenuation control, wide dynamic range can be achieved without requiring a wide dynamic range RF VGA block.

For validation of the proposed architecture, a radio frequency (RF) pulse generator is implemented with Taiwan Semiconductor Manufacturing Company (TSMC) 0.18μm 1P6M Mixed Signal CMOS process. The measurement results show that using the proposed technique, wide dynamic range pulse-modulated polar transmitters can be implemented accurately with ease. An RF VGA with just 21 dB of dynamic range is sufficient to pass the 80 dB power control range of the CDMA2000 standard. Measurement results also show that a DAC with 8-bit resolution for the envelope path and two DACs with 8-bit resolution for the phase path are sufficient to pass the ACPR requirements of the CDMA2000 standard. Compared to a conventional transmitter utilizing linear PAs, the proposed architecture would have lower cost and achieve much higher efficiency.