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A Study on High Efficiency High Voltage Envelope Tracking RF Power Amplifier : 고효율 고전압 포락선 추적 전력 증폭기에 관한 연구
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- Authors
- Advisor
- 서광석
- Major
- 공과대학 전기·컴퓨터공학부
- Issue Date
- 2017-08
- Publisher
- 서울대학교 대학원
- Keywords
- Broadband ; class-J ; class-E2resonant converter ; CMOS ; dc-dc converter ; digital pre-distortion (DPD) ; efficiency ; envelope amplifier (EA) ; envelope tracking (ET) ; GaN ; long term evolution (LTE) ; long term evolution-advanced (LTE-A) ; multiband ; power amplifier (PA) ; silicon-on-insulator (SOI) ; stacked FET ; VCO ; wideband.
- Description
- 학위논문 (박사)-- 서울대학교 대학원 공과대학 전기·컴퓨터공학부, 2017. 8. 서광석.
- Abstract
- In this dissertation, two advanced techniques to solve system issues in envelope tracking power amplifier (ET PA) is presented.
First of all, a two-stage broadband CMOS stacked FET RF power amplifier (PA) with a reconfigurable interstage matching network is developed for wideband envelope tracking (ET). The proposed RF PA is designed based on Class-J mode of operation, where the output matching is realizedwith a two-section low-pass matching network. To overcome the bandwidth (BW) limitation from the high- interstage impedance, a reconfigurable matching network is proposed, allowing a triple frequency mode of operation using two RF switches. The proposed RF PA is fabricated in a 0.32-μm silicon-on-insulator CMOS process and shows continuous wave (CW) power-added efficiencies (PAEs) higher than 60% from 0.65 to 1.03 GHz with a peak PAE of 69.2% at 0.85 GHz. The complete ET PA system performance is demonstrated using the envelope amplifier fabricated on the same process. When measured using a 20-MHz BW long-term evolution signal, the overall system PAE of the ET PA is higher than 40% from 0.65 to 0.97 GHz while evolved universal terrestrial radio access (E-UTRA) adjacent channel leakage ratios (ACLRs) are better than –33 dBc across the entire BW after memoryless digital pre-distortion. To our knowledge, this study represents the highest overall system performance in terms of PAE and BW among the published broadband ET PAs, including GaAs HBT and SiGe BiCMOS.
Second, a high-efficiency gallium-nitride (GaN) envelope amplifier (EA) is developed using class-E2 architecture for wideband LTE applications. The proposed EA consists of a class-E2 resonant converter which output voltage is controlled by a frequency modulator. With a pulse frequency modulation (PFM) signal, the output of the converter can achieve a linear response to the input wideband envelope signal. The frequency modulator with a cross-coupled oscillator and a driver using stacked-FETs structure is fabricated using 0.28-μm SOI CMOS process. The class-E2 converter and PA have been implemented using a commercial GaN device. The envelope amplifier (EA) achieves 74.7% efficiency into a 50 Ω load for a 20-MHz BW LTE signal with a 7.5 dB peak-to-average power ratio (PAPR) and there is no efficiency degradation as the LTE signal bandwidth increases to 160-MHz. The ET transmitter system demonstrated using the CMOS and GaN shows an overall system efficiency of 47.4% at 35.4 dBm with 20-MHz BW LTE signal centered at 3.5 GHz. The measured E-UTRA ACLR of ET PA is –33.8 dBc at 34.4 dBm output power before linearization and –42.9 dBc at the same output power after memory digital pre-destination (DPD). When tested using 80-MHz BW LTE signal, the overall system PAE reaches 46.5% at 35.3 dBm output power and E-UTRA ACLR was measured by –31.5 dBc at 34.4 dBm output power. A wideband performance is characterized using various bandwidth LTE signals which shows only 2.3 dB ACLR degradation without PAE degradation as the signal bandwidth is increased from 20- to 80-MHz. The proposed method is a first demonstration of GaN EA cover 160-MHz BW LTE signals and overcomes the efficiency degradation of the conventional EA as the signal bandwidth increase.
- Language
- English
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