Efficiency enhancement of the Doherty amplifier for 3.5 GHz WiMAX application using class‐F circuitry

This article presents a high‐power and high‐efficiency saturated Doherty amplifier using a GaN high electron mobility transistor for 3.5 GHz Worldwide Interoperability for Microwave Access application.The saturated Doherty amplifier is a Doherty amplifier based on class‐F amplifiers, resulting in higher efficiency than a conventional Doherty amplifier. The distributed‐type harmonic control circuit is located between a power transistor and an output matching circuit. From the measured results for a continuous wave of 3.5 GHz, the saturated Doherty amplifier attains a high P 3dB of 45 dBm and a power gain of about 8.8 dB. Also, the proposed Doherty amplifier provides a high power‐added‐efficiency (PAE) of 37.7% and a drain efficiency of 42.7% at 6‐dB back‐off output power region from P 3dB , which are 8.7% and 5.7% higher than those of the conventional Doherty amplifier. Compared to the single class‐AB amplifier, we obtain 17.7% and 19.7% improvement of PAE and drain efficiency, respectively. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 52: 570–573, 2010; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.24977