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Doherty Amplifier Design Using a Compact Slow-Wave Microstrip Branch-Line coupler for Linearity Improvement  

Kim, Tae-Hyung (Information and Telecommunication Engineering, Soongsil University)
Seo, Chul-Hun (Information and Telecommunication Engineering, Soongsil University)
Publication Information
Journal of the Institute of Electronics Engineers of Korea TC / v.45, no.9, 2008 , pp. 55-59 More about this Journal
Abstract
In this paper, the linearity of Doherty amplifier has been improved by applying a compact slow-wave microstrip branch-line coupler on the output of Doherty amplifier. The proposed branch coupler has four microstrip high-low impedance resonant cells periodically placed inside the branch-line coupler to result in high slow-wave effect. The new coupler not only effectively reduces the occupied area to 30% of the conventional branch-line coupler at 1.8GHz, but also has high second harmonic suppression performance. We obtained the 3rd-order intermodulation distortion ($IMD_3$) of -31.16 dBc for CDMA applications with that of maintaining the constant power added efficiency (PAE). The IMD3 performance is improved as much as -7 dBc compared with a Doherty amplifier.
Keywords
Doherty Amplifier; Compact Slow-Wave Microstrip Branch-Line Coupler; PBG; Linearity;
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  • Reference
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