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http://dx.doi.org/10.5515/JKIEES.2011.11.1.016

GaN HEMT Based High Power and High Efficiency Doherty Amplifiers with Digital Pre-Distortion Correction for WiBro Applications  

Park, Jun-Chul (School of Electrical & Electronic Engineering, Yonsei University)
Kim, Dong-Su (Korea Electronics Technology Institute)
Yoo, Chan-Sei (Korea Electronics Technology Institute)
Lee, Woo-Sung (Korea Electronics Technology Institute)
Yook, Jong-Gwan (School of Electrical & Electronic Engineering, Yonsei University)
Chun, Sang-Hyun (Department of Radio Science and Engineering, Kwangwoon University)
Kim, Jong-Heon (Department of Radio Science and Engineering, Kwangwoon University)
Hahn, Cheol-Koo (Korea Electronics Technology Institute)
Publication Information
Journal of electromagnetic engineering and science / v.11, no.1, 2011 , pp. 16-26 More about this Journal
Abstract
This paper presents high power and high efficiency Doherty amplifiers for 2.345 GHz wireless broadband (WiBro) applications that use a Nitronex 125-W ($P_{3dB}$) GaN high electron mobility transistor (HEMT). Two- and three-way Doherty amplifiers and a saturated Doherty amplifier using Class-F circuitry are implemented. The measured result for a center frequency of 2.345 GHz shows that the two-way Doherty amplifier attains a high $P_{3dB}$ of 51.5 dBm, a gain of 12.5 dB, and a power-added efficiency (PAE) improvement of about 16 % compared to a single class AB amplifier at 6-dB back-off power region from $P_{3dB}$. For a WiBro OFDMA signal, the Doherty amplifier provides an adjacent channel leakage ratio (ACLR) at 4.77 MHz offset that is -33 dBc at an output power of 42 dBm, which is a 9.5 dB back-off power region from $P_{3dB}$. By employing a digital pre-distortion (DPD) technique, the ACLR of the Doherty amplifier is improved from -33 dBc to -48 dBc. The measured result for the same frequency shows that the three-way Doherty amplifier, which has a $P_{3dB}$ of 53.16 dBm and a gain of 10.3 dB, and the saturated Doherty amplifier, which has a $P_{3dB}$ of 51.1 dBm and a gain of 10.3 dB, provide a PAE improvement of 11 % at the 9-dB back-off power region and 7.5 % at the 6-dB back-off region, respectively, compared to the two-way Doherty amplifier.
Keywords
Class-F; Digital Pre-Distortion (DPD); Doherty Amplifier; Gallium Nitride (GaN); WiBro;
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