• 대한전자공학회논문지TC
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• 제46권1호
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• pp.102-106
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• 2009

본 논문은 EER(Envelope Elimination and Restoration)에 적용된 class F 전력 증폭기의 드레인 전압의 변화에 따른 출력 정합회로의 최적화에 대하여 연구하였다. EER 구조에 적용된 class F PA의 PAE(Power Added Efficiency)를 개선하기 위해 고조파 조정 회로에 Varactor 다이오드를 사용하였다. 포락선의 변화에 따라 2차 고조파는 단락 시키고 3차 고조파는 개방 시키도록 설계되었으며 본 논문에서 제안된 고조파 조정 회로를 통해 드레인 전압이 25 V에서 30 V까지 변화할 때 수 %의 PAE 개선 효과를 얻을 수 있었다.

• 한국위성정보통신학회논문지
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• 제5권2호
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• pp.82-86
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• 2010

본 논문에서는 포락선추적 기능을 갖는 WCDMA 기지국에 사용될 수 있는 GaN FET를 이용한 전력증폭기 모듈을 설계하고, 제작 및 측정결과를 제시하였다. 개발된 전력증폭기 모듈은 소신호 RF 신호를 입력받아 고이득 MMIC 증폭기, 구동 증폭기 및 전력 증폭기 등을 거쳐 10W 이상의 출력을 생성할 수 있다. 또한, Envelope Tracking 응용을 위해서 최종 전력증폭기의 Drain 전압이 가변되어도 전체 모듈이 안정적으로 동작할 수 있도록 발진방지회로, Isolator, 음전압 우선인가 바이어스 회로가 설계되었다. 모든 바이어스 회로와 RF회로를 $17.8{\times}9.8{\times}2.0\;cm3$ 크기의 하우징 안에 집적화하여 소형화시켰다. 측정결과 바이어스 전압이 4V에서 28V까지 가변할 경우 30dBm에서 40dBm까지 출력이 가변되면서도 35%이상의 일정한 효율 특성을 나타내어 포락선 추적 기능을 수행할 수 있음을 확인하였다.

• Journal of electromagnetic engineering and science
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• 제15권2호
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• pp.63-75
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• 2015

The CMOS power amplifier (PA) is a promising solution for highly-integrated transmitters in a single chip. However, the implementation of PAs using the CMOS process is a major challenge because of the inferior characteristics of CMOS devices. This paper focuses on improvements to the efficiency and linearity of CMOS PAs for modern wireless communication systems incorporating high peak-to-average ratio signals. Additionally, an envelope tracking supply modulator is applied to the CMOS PA for further performance improvement. The first approach is enhancing the efficiency by waveform engineering. In the second approach, linearization using adaptive bias circuit and harmonic control for wideband signals is performed. In the third approach, a CMOS PA with dynamic auxiliary circuits is employed in an optimized envelope tracking (ET) operation. Using the proposed techniques, a fully integrated CMOS ET PA achieves competitive performance, suitable for employment in a real system.

• Journal of electromagnetic engineering and science
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• 제14권1호
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• pp.1-8
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• 2014

A differential-cascode CMOS power amplifier (PA) with a supply modulator for envelope tracking (ET) has been implemented by 0.18 ${\mu}m$ RF CMOS technology. The loss at the output is minimized by implementing the output transformer on a FR-4 printed circuit board (PCB). The CMOS PA utilizes the $2^{nd}$ harmonic short at the input to enhance the linearity. The measurement was done by the 10MHz bandwidth 16QAM 6.88 dB peak-to-average power ratio long-term evolution (LTE) signal at 1.85 GHz. The ET operation of the CMOS PA with the supply modulator enhances the power-added efficiency (PAE) by 2.5, to 10% over the stand-alone CMOS PA for the LTE signal. The ET PA achieves a PAE of 36.5% and an $ACLR_{E-UTRA}$ of -32.7 dBc at an average output power of 27 dBm.

• 전기학회논문지
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• 제66권8호
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• pp.1215-1221
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• 2017

Parametric array transducers are used for highly directional speaker in an air environments. Piezoelectric micromachined ultrasonic transducers for parametric array transducers need DC-biased voltage driving signals in order to get high-directional quality-sound features. The existing power amplifier such as class A amplifiers has low efficiency and require large volume heatsinks. To overcome the above-mentioned disadvantages of the conventional amplifier, this paper proposes a new power amplifier system. The proposed power amplifier system ensures high linearity of output characteristic by utilizing the push-pull class B type amplifier. Furthermore, the proposed power amplifier system gets high efficiency because it contains the DC-DC converter-type power supply which can perform energy recovery and envelope tracking function. Also the paper suggests the detailed circuit topology. Its characteristics are verified by the detailed experimental results.

• 전력전자학회논문지
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• 제19권4호
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• pp.364-375
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• 2014

Parametric array transducers are used for long-range and highly directional communication in an underwater environments. The power amplifiers for parametric array transducers should have sufficient linear output characteristic and high efficiency to avoid communication errors, system heating, and fuel problems. But the conventional power amplifier with fixed source voltage is very low efficient due to large power loss by the big difference between the fixed source voltage and the amplifier output voltage. Thus to solve the problems this paper proposes the high efficiency power amplifier for parametric array transducers. The proposed power amplifier ensures high linearity of output characteristic by utilizing the push-pull class B type amplifier and furthermore gets high efficiency by applying the envelope tracking technique that variable source voltage tracks the envelope of the amplified signal. Also the paper suggests the detailed circuit topology and design guideline of class B push-pull type amplifier and variable output voltage AC/DC converter. Its characteristics are verified by the detailed simulation and experimental results.

• 전력전자학회논문지
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• 제18권1호
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• pp.72-83
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• 2013

The paper proposes a new multilevel variable output voltage AC/DC Converter for power supply of power amplifiers used in underwater acoustic sensors. The proposed multilevel variable output voltage AC/DC Converter is composed of two parts. One as the input section is the high efficiency phase-shifted PWM full bridge DC-DC converter to get multiport power sources. The other as the output section is composed of two flying-capacitor 3-level DC-DC converters and a diode bridge circuit to get fast-response and multilevel variable output voltage for an envelope amplifier. Also the paper suggests the detailed circuit topology and design guideline of multilevel variable output voltage AC/DC converter. It also proposes the power balanced control method between 3-level converters and the voltage balanced algorithm for flying capacitors. Its characteristics should be verified by the detailed simulation results. It is anticipated that the proposed converter will be used very well for power amplifiers used in underwater acoustic sensors.

• 대한전자공학회논문지TC
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• 제39권9호
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• pp.44-50
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• 2002

최근 RF 입력레벨의 크기에 따라 공급되는 바이어스를 변화시켜 효율을 개선하는 포락선 추적 증폭기를 CDMA방식을 채택하는 단말기의 전력증폭기로 사용하려고 시도되고 있다. 그러나 포락선 추적 증폭기는 바이어스가 변함에 따라 증폭기의 입력과 출력 임피던스가 변화되어 이득이 감소하고 효율이 떨어지며 VSWR특성이 악화되는 본질적인 문제가 발생한다. 본 논문에서는 이러한 부정합 문제와 증폭기에서의 이득 및 효율을 개선한 2가지 형태의 포락선 추적증폭기를 제안하였다. 실험적으로 바렉터 다이오드를 이용한 포락선 증폭기의 경우 이득은 약 7dB 개선되었으며, 전력소모는 일반 전력 증폭기에 비해 약 60%개선되었고, 베이스 전압 변화형 포락선 추적 증폭기의 경우 전력 소모는 40%, 이득은 9dB의 개선 효과가 있었다.