應用於5G功率放大器之封包追蹤頻寬達100MHz的混合式電源轉換器

A Hybrid Supply Modulator Achieving 100MHz Envelope Tracking Bandwidth for 5G Power Amplifier

熊珮妤(Pei-Yu Hsiung)

指導教授 ： 陳景然

國立臺灣大學/電機資訊學院/電機工程學研究所/碩士(2022年)

https://doi.org/10.6342/NTU202200478

摘要

封包追蹤電源轉換器透過提供追蹤射頻功率放大器輸出封包而不是固定的電源電壓來提高射頻功率放大器的效率。通常線性放大器輔助開關轉換器會以並聯組合形式於封包追蹤電源轉換器的系統中，取代單獨使用線性放大器或開關轉換器，以追求更好的功率效率。然而，要設計具有100MHz頻寬和高效率的電源調製器是一項挑戰。
本論文提出了一種利用具有快速瞬態響應的開關轉換器與寬頻寬線性放大器實現的混合型電源轉換器。根據效率分析的結果，所提出的線性放大器設計為在較低的電源電壓下運行，將峰值效率提高7%以上。藉由兩種補償方式，加上部分片上交流耦合電容，使線性放大器的單位增益頻寬超過670MHz，滿足第五代 (5G) 通訊之嚴格頻寬要求。而所提出的具有快速交流耦合電容跨壓跟踪路徑的開關轉換器可以將交流耦合電容值降低到100nF，並同時降低線性放大器對電源電壓值的要求。本論文所提出的封包電源轉換器採用TSMC 0.18μm技術的IC中實現。根據測量結果，提出的混合型轉換器在跟踪100MHz正弦波時峰值功率效率達到76％，且輸出電壓在第一和第二音調差為22.6 dB。

關鍵字

封包追蹤 ； 電源轉換器 ； 交流耦合技術 ； 第五代通訊 ； 功率放大器

並列摘要

An Envelope Tracking Supply Modulator (ETSM) improves the efficiency of the radio frequency power amplifier (RFPA) by providing a supply voltage that tracks the envelope of RFPA output instead of a fixed DC voltage. Linear amplifier (LA) assisted switching supply modulator (SW) is combined in parallel for the ETSM system to pursue better power efficiency instead of LA or SW only. However, it is a challenge to design the supply modulator with 100MHz bandwidth and high efficiency.
This thesis presents a hybrid supply modulator utilizing a fast transient response SW and a wide bandwidth LA. As a result of efficiency analysis, the proposed LA is designed to operate at a lower power supply voltage, increasing the peak efficiency by more than 7%. Through two compensation methods and the addition of the partial on-chip AC-coupling capacitor, the unity-gain bandwidth of LA exceeds 670MHz to meet the strict bandwidth requirement of 5th generation (5G). The proposed SW with the fast VCAP tracking path is designed to reduce the AC-coupling capacitance to 100nF and lower the requirement of the LA supply voltage value. The proposed hybrid supply modulator is fabricated in a 180-nm CMOS process. The measurement result shows the tracking of 100MHz sinusoidal signal with 76% peak efficiency at 2-W output power and the measured 1st and 2nd tone difference reaches 22.6dB.

並列關鍵字

Envelope Tracking ； Supply Modulator ； AC-coupling Technique ； Fifth-generation (5G) Communication ； Power Amplifier (PA)

參考文獻

Jake Hertz, “Once 5G hits, DC-DC supply modulators may be RF power amplifier’s saving grace,” July 01, 2020.

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W. Chu, B. Bakkaloglu and S. Kiaei, "A 10 MHz bandwidth, 2 mV ripple PA regulator for CDMA transmitters," IEEE Journal of Solid-State Circuits, vol. 43, no. 12, pp. 2809-2819, Dec. 2008.