Analysis of a Fully Matched Saturated Doherty Amplifier With Excellent Efficiency

Jangheon Kim,Junghwan Moon,Young Yun Woo,Sungchul Hong,Ildu Kim,Jungjoon Kim,Bumman Kim IEEE 2008 IEEE transactions on microwave theory and techniqu Vol.56 No.2

<P>A saturated Doherty amplifier based on class-F amplifiers is analyzed in terms of its load modulation behavior, efficiency, and linearity. Simulations included the amplitude ratio and phase difference between the fundamental and third harmonic voltages, the current/voltage waveforms, load lines, and the third-order intermodulation amplitudes/phases of the carrier and peaking amplifiers. The saturated doherty power amplifier was implemented using two Eudyna EGN010MK GaN HEMTs with a 10-W peak envelope power. For a 2.14-GHz forward-fink wideband code-division multiple-access signal, the doherty amplifier delivers an excellent efficiency of 52.4% with an acceptable linearity of -28.3 dBc at an average output power of 36 dBm. Moreover, the amplifier can provide the high linearity performance of -50 dBc using the digital feedback predistortion technique.</P>

Improving the Linearity of CMOS LNA Using the Post IM3 Compensator

Jingook Kim,Changjoon Park,Huijung Kim,Bumman Kim,Youngsik Kim 한국전자파학회JEES 2007 Journal of Electromagnetic Engineering and Science Vol.7 No.2

In this paper, a new linearization method has been proposed for a CMOS low noise amplifier(LNA) using the Post IM3 Compensator. The fundamental operating theory of the proposed method is to cancel the IM3 components of the LNA output signal by generating another IM3 components, which are out-phase with respect to that of the LNA, from the Post IM3 Compensator. A single stage common-source LNA has been designed to verify the linearity improvement of the proposed method through 0.13 ㎛ RF CMOS process for WiBro system. The designed LNA achieves +7.8 ㏈m of input-referred 3<SUP>rd</SUP>-order intercept point (ⅡP3) with 13.2 ㏈ of Power Gain, 1.3 ㏈ of noise figure and 5.7 mA @1.5 V power consumption. IIP3 is compared with a conventional single stage common-source LNA, and it shows IIP3 is increased by +12.5 ㏈ without degrading other features such as gain and noise figure.

Saturated Power Amplifier Optimized for Efficiency Using Self-Generated Harmonic Current and Voltage

Jungjoon Kim,Jangheon Kim,Junghwan Moon,Jungwhan Son,Ildu Kim,Seunghoon Jee,Bumman Kim IEEE 2011 IEEE transactions on microwave theory and techniqu Vol.59 No.8

<P>A saturated power amplifier (PA) optimized for efficiency is described. As a PA is driven into saturated operation, the current source of the device generates a large third harmonic current, which creates a quasi-rectangular current waveform. The large nonlinear output capacitor of the transistor generates a second harmonic voltage with a very small third harmonic component. The second harmonic voltage is in-phase with the fundamental voltage, making a half-sine wave voltage waveform with voltage peaking. These waveforms are similar to those of a class F<SUP>-1</SUP> . The fundamental load at the intrinsic device is resistive with the output capacitance tuned out, which is identical to the class F<SUP>-1</SUP> case. However, the required harmonic impedances are just larger than the impedance levels of the output capacitance for both the second and third harmonics. Therefore, the circuit topology is similar to that of a class E amplifier, which is very simple. The PA implemented using a GaN HEMT delivers the expected good performance using the simple circuit topology.</P>

IEEE 802.16e Mobile WiMAX용 고효율 고출력 하이브리드 포락선 제거 및 복원 전력 송신기

김일두(Ildu Kim),문정환(Junghwan Moon),김장헌(Jangheon Kim),김정준(Jungjoon Kim),김범만(Bumman Kim) 한국전자파학회 2008 한국전자파학회논문지 Vol.19 No.8

본 논문에서는 효율이 특화된 전력 증폭기를 이용하여 IEEE 802.16e Mobile WiMAX용 고출력 하이브리드 포락선 제거 및 복원 전력 송신기에 대해 기술하였다. Nitronex사의 100-W PEP를 갖는 GaN HEMT 소자를 이용하여 중요한 전력 생성 Vds 구간에 대하여 최대 PAE를 가질 수 있도록 전력 증폭기를 설계하였다. 고출력 응용을 위해서 하이브리드 포락선 제거 및 복원 전력 송신기는 전력 증폭기의 bias fluctuation 문제 및 바이어스 변조기의 stability 문제에 의한 regenerative 오실레이션 문제를 반드시 고려하여 설계되어야 한다. 연동 실험을 위하여, 8.5 ㏈의 PAPR을 갖는 포락선 신호에 대해 바이어스 변조기는 30 V의 최대 출력 전압 크기를 가지면서 72 %의 높은 효율을 유지하도록 구현되었다. WiMAX 신호를 목표로 구현된 하이브리드 포락선 제거 및 복원 전력 송신기는 41.25 ㏈m의 출력 전력에서 38.8 %의 높은 PAE 성능을 얻었다. 또한, 디지털 전치 왜곡 기술을 적용함으로써 전력 송신기의 RCE 성능은 -34.5 ㏈를 기록하여 WiMAX 신호의 선형화 지표를 만족시킬 수 있었다. 본 연구는 2.655 ㎓ 주파수 대역에서 처음으로 구현된 WiMAX용 고출력 하이브리드 포락선 제거 및 복원 전력 송신기에 관한 것이다. We have described a high power hybrid envelope elimination and restoration(H-EER) transmitter for IEEE 802.16e Mobile World Interoperability for Microwave Access(WiMAX) using an efficiency optimized power amplifier(PA). The PA has been designed to have maximum PAE at the important power generation Vds region using Nitronex 100-W PEP GaN HEMT. For the high power application, H-EER transmitter should be considered the regenerative oscillation problem due to the PA’s bias fluctuation effect and bias modulator stability issue. Therefore, the bias modulator for H-EER transmitter has been designed to suppress the regenerative oscillation. For the interlock experiment, the bias modulator has been built with the efficiency of 72 % and peak output voltage of 30 V for the envelope signal with a PAPR of 8.5 ㏈. The H-EER transmitter for WiMAX application has been achieved a high PAE characteristic, 38.8 % at an output power of 41.25 ㏈m. By using digital predistortion(DPD) technique, the Relative Constellation Error (RCE) has been satisfied the specification of -34.5 ㏈. This is the first work at 2.655 ㎓ high power H-EER transmitter for WiMAX application.

Efficiently Amplified

Bumman, Kim,Junghwan, Moon,Ildu, Kim IEEE 2010 IEEE microwave magazine Vol.11 No.5

<P>Modern wireless communication systems have evolved to support increasing numbers of subscribers and provide higher data rate services within the limited frequency resources. As part of this evolution, many transmitted signals in the new standards, such as WCDMA, long term evolution (LTE), and worldwide interoperability for microwave access (WiMAX), now utilize a high peak-to-average power ratio (PAPR) caused by complex modulation schemes, generating the rapid change in the magnitude of signal as shown in Figure 1(a). In particular, as depicted in Figure 1(b), the PAPRs of the signals exceed 9 dB at 0.01% level of complementary cumulative distribution function. Use of high PAPR signals result in the power amplifier (PA) operating at a large enough back-off to satisfy the stringent linearity requirement. However, in this region, efficiency of the PA is very low. To bolster low efficiency in the back-off region, various efficiency boosting techniques have been considered over time. Recently, due to high-efficiency capabilities [1]–[13], supply voltage modulated PAs, such as envelope elimination and restoration (EER), hybrid-EER (H-EER), and envelope tracking (ET) technique, have received a lot of attention. Excellent experimental results have been reported using the various device technologies and modulated signals, as summarized in Table 1.</P>

Advanced Doherty Architecture

Kim, Bumman,Kim, Ildu,Moon, Junghwan IEEE 2010 IEEE microwave magazine Vol.11 No.5

<P>For modulated signals with a high peak-to-average power ratio (PAPR), the transmitter has to be operated with its average output power backed off for an acceptable linearity at the expense of low efficiency. To achieve high efficiency and high linearity at the same time, both an efficiency enhancement technique and a linearization technique should be utilized. A powerful and reliable linearization technique, digital predistortion (DPD), is currently the most favored method for the linearization of base-station amplifiers [1]–[3]. Possible efficiency enhancement techniques are the hybrid envelope elimination and restoration/envelope tracking technique (H-EER/ET) and the Do-herty technique.</P>

A highly efficient class-F power amplifier for wideband linear power amplifier applications

Kim, Jangheon,Moon, Junghwan,Hong, Sungchul,Kim, Bumman Wiley Subscription Services, Inc., A Wiley Company 2009 MICROWAVE AND OPTICAL TECHNOLOGY LETTERS Vol.51 No.10

<P>In this letter, a highly efficient class-F power amplifier (PA) is developed as a new main block of the wideband base-station linear power amplifier. The class-F PA is implemented using Eudyna EGN010MK GaN HEMT with a 10-W peak envelop power. The nonlinearity and memory effects of class-F PA are explored to apply the wideband application. The maximum power-added efficiency of the implemented PA is 68% at a saturated output power of 40 dBm for the 2.14-GHz CW signal. The PA delivers a good efficiency of 35% at an average output power of 32.3 dBm for wide-band code division multiple access 3FA signal with 15-MHz bandwidth, and the linearity can be improved to about −48 dBc using the digital feedback predistortion linearization technique. © 2009 Wiley Periodicals, Inc. Microwave Opt Technol Lett 51: 2323–2326, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24631</P>

Highly Efficient Dual-Switch Hybrid Switching Supply Modulator for Envelope Tracking Power Amplifier

Dongsu Kim,Daehyun Kang,Jooseung Kim,Yunsung Cho,Bumman Kim IEEE 2012 IEEE microwave and wireless components letters Vol.22 No.6

<P>This letter describes a highly efficient dual-switch hybrid switching supply modulator for an envelope tracking power amplifier (PA). The supply modulator has a combined structure of a linear amplifier and a switching amplifier. For an improved efficiency, the switching amplifier employs two buck converters and realizes an adaptive slew rate control of the switching amplifier's current. An implemented envelope tracking PA delivers an efficiency of 39.1% at an output power of 27 dBm for long term evolution signal with 10 MHz channel bandwidth.</P>

A Saturated Doherty Power Amplifier Based On Saturated Amplifier

Jangheon Kim,Junghwan Son,Junghwan Moon,Bumman Kim IEEE 2010 IEEE microwave and wireless components letters Vol.20 No.2

<P>A saturated Doherty power amplifier (PA) based on the saturated PA tuned by the self-generated harmonic currents is presented. When driven with mobile WiMAX 1FA signal, this Doherty PA demonstrates high efficiency performance (average 57%) over the WiMAX band from 2.5 GHz to 2.7 GHz. Simulated and experimental results allow the evaluation for the load modulation behavior of the saturated PA and bandwidth correlation between the Doherty and saturated unit PAs. The linearity requirement of the WiMAX signal is met using the digital feedback predistortion linearization technique.</P>

Analysis of Adaptive Digital Feedback Linearization Techniques

Jangheon Kim,Changjoon Park,Junghwan Moon,Bumman Kim IEEE 2010 IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS PART 1 R Vol.57 No.2

<P>A new lookup-table linearization technique is developed based on the digital feedback and digital feedback/predistortion (DFBPD) concepts. The linearization characteristics are investigated through system simulation of a real power-amplifier model with 90-W peak envelope power. The DFB suppresses forward-path nonlinear distortion as a gain reduction due to the FB effect, and this technique enhances the system tolerance without any bandwidth limitation. As the PD network is added to the FB loop, the linearization performance and system tolerance are further improved because of more accurate PD signal extraction. In addition, the gain is purely determined by the FB path, so the gain fluctuation in the forward path, including amplifier aging and temperature effects, is suppressed. The analysis and simulation allow experimental evaluation of the linearization mechanism and performance of the DFBPD technique for an 802.16 e mobile Worldwide Interoperability for microwave access signal.</P>