CMOS로 제어되는 GaN HEMT Supply Modulator를 이용한 고효율 Average Power Tracking 전력 증폭기

학위논문 (석사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2013. 8. 권영우.본 논문에서는 Cree사의 CGH60시리즈 GaN HEMT bare die칩으로 제작된 PA를 이용한 Average Power Tracking (APT) 시스템이 구현되었다. 전원 변조기의 제어 회로로써 IBM 0.18um SOI 2.5V RF 공정이 사용되었다. 전원 변조기로는 Class E2 DC-DC컨버터가 사용되었다. Class-E 인버터와 Class-E정류기에 필요한 스위치로는 GaN HEMT가 사용되었다. 두 스위치 모두 CMOS회로에서 펄스 폭 변조 (PWM)방식으로 만들어진 펄스로 제어되었다. 공급 전압 28V와 1MHz PWM신호를 사용한 결과 듀티가 0.5일 때 최대 효율 85%와 31V의 출력 전압을 얻을 수 있었다. GaN HEMT를 이용하여 5.8GHz 고효율 2-단 Class-E 전력 증폭기도 제작되었다. 수치 해석적으로 초기 디자인이 진행되었으며, lumped 소자들은 모두 마이크로스트립으로 대체되었다. 측정 결과 39dBm에서 63.9%의 효율을 얻을 수 있었으며 그때의 전력 이득은 15.8dB였다. Power-단의 드레인 효율은 76%였다. 백오프 구간에서의 효율을 올리기 위해 APT 시스템이 적용되었다. 시스템의 Power-단 드레인 효율은 6dB 백오프 지점에서 1%증가하였으며 9dB 백오프 지점에서 5.7% 증가하였다. 전원 변조기의 최대 출력 전압은 32V로 부스팅 되기 때문에 최대 출력 전력은 37.9dBm에서 38.7dBm으로 증가하였다. 전원 변조기를 제어하기 위해 펄스 폭과 주파수 변조 (PWFM)방식이 PWM대신 제안되었다. 제안된 전원 변조기는 12V출력전압일 때 11%의 효율 증가를 보여주었으며 따라서 넓은 출력 전압 영역에서 70%이상의 효율을 보여주었다. 같은 PA에 APT를 적용한 결과 39.6dBm에서 최대 PAE 49.5%를 얻을 수 있었다. 6dB와 9dB백오프 지점에서의 효율은 각각 4%와 3.5%씩 증가하였다.In this thesis, an Average Power Tracking (APT) system of a Power Amplifier (PA) using Cree Inc. CGH60 series GaN HEMT bare die is presented. IBM 0.18um SOI 2.5V RF technology is used to fabricate control circuits in supply modulator. A Class E2 DC-DC Converter is adopted as the supply modulator. Both Class-E inverter switch and Class-E rectifier switch uses GaN HEMT as a switch. Both switches are controlled by Pulse Width Modulation (PWM) generated by CMOS control circuit. The peak efficiency is 85% at 31V of output voltage with 0.5 duty cycle of 1MHz PWM when 28V is supplied. Highly efficient 5.8GHz 2-Stage Class-E Power Amplifier is realized with GaN HEMT device. Numerical analysis has performed for initial design of PA then the ideal lumped elements are replaced with microstrip lines. The measurement results show the maximum PAE of 63.9% at 39.0dBm of output power with 15.8dB gain. The maximum power-stage drain efficiency is 76% Average Power Tracking is applied in order to increase power-stage drain efficiency at back-off power. The system shows 1% of drain efficiency increment at 6-dB back-off and 5.7% increment at 9-dB back-off power. Since the supply modulator boosts up to 32-V, the maximum output power is increased to 38.7dBm from 37.9dBm. Pulse Width and Frequency Modulation (PWFM) control method is introduced in place PWM control in supply modulator. The new supply modulator shows 11% of efficiency increment at 12V resulting in higher than 70% of efficiency over wide output voltage range. When Average Power Tracking is applied with the same PA, the peak PAE of 49.5% at 39.6dBm with gain of 15.6dB is resulted. At 6 dB and 9 dB back-off power, 4% and 3.5% of PAE is increased.Abstract Table of Contents List of Figures List of Tables 1. Introduction 2. Supply Modulator 2.1. Introduction 2.2. Class E2 DC-DC Converter 2.3. PWM Controlled Supply Modulator 2.3.1. Pulse Width Modulation (Inverter Switch Control) 2.3.2. Rectifier Switch Control 2.4. CMOS Control Circuit 2.4.1. Operational Amplifier 2.4.2. Comparator 2.4.3. Hysteresis Comparator 2.4.4. Voltage Regulator 2.4.5. Gate Driver 2.4.6. Layout 2.5. Measurement: Hybrid Modulator with CMOS and GaN HEMT 2.5.1. CMOS Control Circuit Results 2.5.2. Hybrid Modulator Results 2.6. Future Work 2.7. Conclusion 3. Power Amplifier 3.1. Introduction 3.2. Class E Power Amplifier 3.3. Extraction of Parasitic Elements 3.4. Two-Stage Class-E Power Amplifier 3.4. Measurement: Class E Two Stage Power Amplifier 3.5. Conclusion 4. Average Power Tracking System I 4.1. Introduction 4.2. Expected Overall PAE Calculation 4.3. Synchronization of Supply Modulator with Power Amplifier 4.3. Measurement: Average Power Tracking Power Amplifier I 4.4. Conclusion 5. Average Power Tracking System II 5.1. Introduction 5.2. Concept of PWFM 5.3. Measurement: PWFM Controlled Supply Modulator 5.4. Highly Efficient 5.8GHz Power Amplifier 5.5. Measurement: Average Power Tracking Power Amplifier II 5.6. Conclusion 6. Conclusion Reference Appendix Notes 초록 AcknowledgementMaste

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