The Journal of Korean Institute of Electromagnetic Engineering and Science (한국전자파학회논문지)

The Korean Institute of Electromagnetic Engineering and Science (한국전자파학회)
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Asymmetric Saturated 3-Stage Doherty Power Amplifier Using Envelope Tracking Technique for Improved Efficiency

효율 향상을 위해 포락선 추적 기술을 이용한 비대칭 포화 3-Stage 도허터 전력 증폭기

  • Kim, Il-Du (Dept. of Electronic and Electrical Engineering, Pohang University of Science and Technology(POSTECH)) ;
  • Jee, Seung-Hoon (Dept. of Electronic and Electrical Engineering, Pohang University of Science and Technology(POSTECH)) ;
  • Moon, Jung-Hwan (Dept. of Electronic and Electrical Engineering, Pohang University of Science and Technology(POSTECH)) ;
  • Son, Jung-Hwan (Dept. of Electronic and Electrical Engineering, Pohang University of Science and Technology(POSTECH)) ;
  • Kim, Jung-Joon (Dept. of Electronic and Electrical Engineering, Pohang University of Science and Technology(POSTECH)) ;
  • Kim, Bum-Man (Dept. of Electronic and Electrical Engineering, Pohang University of Science and Technology(POSTECH))
  • 김일두 (포항공과대학교 전자전기공학부) ;
  • 지승훈 (포항공과대학교 전자전기공학부) ;
  • 문정환 (포항공과대학교 전자전기공학부) ;
  • 손정환 (포항공과대학교 전자전기공학부) ;
  • 김정준 (포항공과대학교 전자전기공학부) ;
  • 김범만 (포항공과대학교 전자전기공학부)
  • Published : 2009.08.31
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Abstract

We have investigated operation of a 1:2:2 asymmetric 3-stage Doherty PA(Power Amplifier) and implemented using the Freescale's 4 W, 10 W PEP LDMOSFETS at 1 GHz. By employing the three peak efficiency characteristics, compared to the two peak N-way Doherty PA, the asymmetric 3-stage Doherty can overcome the serious efficiency degradation along the backed-off output power region and maximize the average efficiency for the modulation signal. To maximize the efficiency characteristic, the inverse class F PA has been designed as carrier and peaking amplifiers. Furthermore, to extract the proper load modulation operation, the adaptive gate bias control signal has been applied to the two peaking PAs based on the envelope tracking technique. For the 802.16e Mobile WiMAX(World Interoperability for Microwave Access) signal with 8.5 dB PAPR(Peak to Average Power Ratio), the proposed Doherty PA has shown 55.46 % of high efficiency at an average output power of 36.85 dBm while maintaining the -37.23 dB of excellent RCE(Relative Constellation Error) characteristic. This is the first time demonstration of applying the saturated PA and adaptive gate bias control technique to the asymmetric 3-stage Doherty PA for the highly efficient transmitter of the base-station application.

본 논문에서는 1:2:2의 비대칭 3-stage 도허티 전력 증폭기의 동작을 살펴보고, Freescale사의 4 W, 10 W LDMOSFET을 이용하여 1 GHz에서 구현하였다. 두 번의 최대 효율 특성을 갖는 N-way 도허티 전력 증폭기와 비교 하였을 때, 비대칭 3-stage 도허티 전력 증폭기는 세 번의 최대 효율 특성을 갖도록 함으로써 백 오프된 출력 전력영역에서의 심각한 효율 저하를 극복할 수 있고, 주어진 변조 신호에서의 평균 효율을 최대화 할 수 있다. 효율 특성을 더욱 최적화하기 위해, 역 F급 전력 증폭기를 캐리어 및 피킹 전력 증폭기로 설계하였다. 또한, 적절한 로드모듈레이션 동작을 이끌어내기 위해, 포락선 추적 방법에 근거한 적응 게이트 바이어스 조절 신호를 두 개의 피킹 전력 증폭기에 인가하였다. 8.5 dB의 PAPR을 갖는 802.16e Mobile WiMAX 신호에 대해 제안된 비대칭 도허티 전력 증폭기는 36.85 dBm에서 55.46 %의 높은 효율 특성을 얻었고, -37.23 dB의 우수한 RCE 특성을 유지하였다. 본 논문에서는 처음으로 포화 증폭기와 적응 게이트 바이어스 조절 신호를 비대칭 3-stage 도허티 전력 증폭기에 적용하였으며, 이를 통해 기지국용 고효율 전력 송신기의 설계가 구현 가능함을 성공적으로 검증하였다.

Keywords

References

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