A Miniature Broadband Doherty Power Amplifier With a Series-Connected Load

A microwave Doherty power amplifier (DPA) consists of a carrier amplifier (CA), a peaking amplifier (PA), and an impedance inverting network. In this paper, a novel DPA topology with neither the impedance inverting network nor offset lines is proposed. This topology enables the enhancement of amplifier bandwidth and achieves a more compact amplifier size. To remove the impedance inverting network and to realize high efficiency at large back-off power level, the output-matching network of the CA is designed to realize high performance both at a low signal power level in the off-state of the PA and at the saturated signal power level. A 1.9-GHz series-connected load Doherty power amplifier without an impedance inverting network is designed and fabricated using GaN HEMTs. The amplifier achieves a power-added efficiency (PAE) of 50% under a 6-dB output back-off from a 34-dBm saturated output power with a PAE of 59%. A maximum PAE higher than 44% is obtained over a frequency range of 1.63-1.98 GHz.

[1]  Dongsu Kim,et al.  Design of Bandwidth-Enhanced Doherty Power Amplifiers for Handset Applications , 2011, IEEE Transactions on Microwave Theory and Techniques.

[2]  W.H. Doherty,et al.  A New High Efficiency Power Amplifier for Modulated Waves , 1936, Proceedings of the Institute of Radio Engineers.

[3]  A. Grebennikov,et al.  A Dual-Band Parallel Doherty Power Amplifier for Wireless Applications , 2012, IEEE Transactions on Microwave Theory and Techniques.

[4]  A. Z. Markos,et al.  Frequency Response Analysis and Bandwidth Extension of the Doherty Amplifier , 2011, IEEE Transactions on Microwave Theory and Techniques.

[5]  G. Ghione,et al.  3–3.6-GHz Wideband GaN Doherty Power Amplifier Exploiting Output Compensation Stages , 2012, IEEE Transactions on Microwave Theory and Techniques.

[6]  F. Giannini,et al.  A Doherty Architecture With High Feasibility and Defined Bandwidth Behavior , 2013, IEEE Transactions on Microwave Theory and Techniques.

[7]  Rolf H. Jansen,et al.  Broadband Doherty Power Amplifier via Real Frequency Technique , 2012, IEEE Transactions on Microwave Theory and Techniques.

[8]  D. Kuylenstierna,et al.  A Wideband and Compact GaN MMIC Doherty Amplifier for Microwave Link Applications , 2013, IEEE Transactions on Microwave Theory and Techniques.

[9]  Y. Takayama,et al.  A High-Efficiency Low-Distortion GaN HEMT Doherty Power Amplifier With a Series-Connected Load , 2012, IEEE Transactions on Microwave Theory and Techniques.

[10]  Ryo Ishikawa,et al.  A GaN HEMT Doherty amplifier with a series connected load , 2009, 2009 Asia Pacific Microwave Conference.

[11]  Shintaro Watanabe,et al.  A broadband Doherty power amplifier without a quarter-wave impedance inverting network , 2012, 2012 Asia Pacific Microwave Conference Proceedings.

[12]  Franco Giannini,et al.  A Wideband Doherty Architecture With 36% of Fractional Bandwidth , 2013, IEEE Microwave and Wireless Components Letters.

[13]  S. Boumaiza,et al.  A Modified Doherty Configuration for Broadband Amplification Using Symmetrical Devices , 2012, IEEE Transactions on Microwave Theory and Techniques.

[14]  F. M. Ghannouchi,et al.  A Transformer-Less Load-Modulated (TLLM) Architecture for Efficient Wideband Power Amplifiers , 2012, IEEE Transactions on Microwave Theory and Techniques.