This paper describes the design of a highly efficient and linear GaN HEMT power amplifier which may be used in WiMAX application. To improve linearity of highly efficient power amplifiers, a technique using diodes in the gate DC path was applied to TL and 2HT amplifier. This solution using diodes offers a good manner to improve linearity near saturation zone compared to the approach using only a DC gate resistor for TL (tuned load) case as well as for 2HT (second harmonic tuning approach). A 2.5 GHz 2HT power amplifier circuit was built, and measured data confirm the linearity improvement, particularly near saturation zone, as predicted by simulation, maintaining higher power performances. An output power of 36.8 dBm has been measured with an associated power added efficiency of 46.5% and carrier to third order intermodulation (C/I3) of 53.4 dBc. A 2HT PA also exhibits good performances across the full (2.3-2.7) GHz band. An output power ranging from (35-36.9) dBm with an associated gain of $12.9±0.9 and a power added efficiency ranging from (40-46)% are measured across the full (2.3-2.7) GHz band.
2. Cripps, S. C., RF Power Amplifiers for Wireless Communications, 2nd Ed., Artech, Boston, MA, 2006.
3. Colantonio, P., F. Giannini, R. Giofrµe, E. Limiti, A. Serino, M. Peroni, P. Romanini, and C. Proietti, "A C-band high efficiency second harmonic tuned hybrid power amplifier in GaN technology ," IEEE Transactions on Microwave Theory and Techniques, Vol. 54, No. 6, Part 2, 2713-2722, Jun. 2006.
4. Wright, P., J. Lees, J. Benedikt, P. J. Tasker, and S. C. Cripps, "A methodology for realizing high efficiency class-J in a linear and broadband PA ," IEEE Transactions on Microwave Theory and Techniques, Vol. 57, No. 12, Part 2, 3196-3204, Dec. 2009.
5. Colantonio, P., F. Giannini, G. Leuzzi, and E. Limiti, "High-efficiency low-IM microwave PA design," IEEE MTT-S Int. Microwave Symp. Dig., Vol. 1, 511-514, Phoenix, AZ, May 2001.
6. Colantonio, P., F. Giannini, G. Leuzzi, and E. Limiti, "Theoretical facet and experimental results of harmonic tuned PAs," International Journal of RF and Microwave Computer-Aided Engineering, Vol. 13, 459-472, 2003.
7. Colantonio, P., F. Giannini, G. Leuzzi, and E. Limiti, Class G Approach for Low Voltage, High-efficiency PA Design, 366-378, ohn Wiley & Sons, Inc., 2000.
8. Colantonio, P., F. Giannini, G. Leuzzi, and E. Limiti, IMD performances of harmonic-tuned microwave power amplifiers, Proc. European Gallium Arsenide Applications Symposium, 132-135, Paris, France, Oct. 2000.
9. Moazzam, M. R. and C. S. Aitchison, A low third order intermodulation amplifier with harmonic feedback circuitry, IEEE MTT-S Int. Microwave Symp. Dig., 827-830, 1996.
10. Raab, F. H., P. Asbeck, S. Cripps, P. B. Kenington, Z. B. Popovic, N. Pothecary, J. F. Sevic, and N. O. Sokal, "Power amplifiers and transmitters for RF and microwave," IEEE Transactions on Microwave Theory and Techniques, Vol. 50, 814-826, Mar. 2002.
11. Cripps, S., Advanced Techniques in RF Power Amplifier Design, Artech House, 2002.
12. Eun, C. and E. J. Powers, "A new Volterra predistorter based on the indirect learning architecture," IEEE Trans. Signal Processing, Vol. 45, 223-227, Jan. 1997.
13. Zhu, A. and T. J. Brazil, "An adaptive volterra predistorter for the linearization of RF high power amplifiers," IEEE MTT-S, 461-464, 2002.
14. Kim, J. and K. Konstantinou, "Digital predistortion of wideband signals based on power amplifier model with memory," Electronics Letters, Vol. 37, No. 23, 1417-1418, Nov. 8, 2001.
15. Nizamuddin, M. A., P. J. Balister, W. H. Tranter, J. H. Reed, "Nonlinear tapped delay line digital predistorter for power amplifiers with memory," IEEE Wireless Communications and Networking, Vol. 1, 607-611, Mar. 2003.
16. Carvalho, N. and J. Pedro, "Large and small signal IMD behavior of microwave power amplifiers," IEEE Transactions on Microwave Theory and Techniques, Vol. 47, 2364-2374, Dec. 1999.
17. Pedro, J. and N. Carvalho, Intermodulation Distortion in Microwave and Wireless Circuits, Artech House, 2003.
18. Cabral, P. M., J. C. Pedro, and N. B. C. Carvalho, "A unified theory for nonlinear distortion characteristics in different amplifier technologies," Microwave Journal, Dec. 2004.
19. Gómez, C., J. A. García, and J. C. Pedro, IMD sweet-spot control on junction FET devices using a gate bias resistor, 34th European Microwave Conf. Proceedings, Amsterdam, 2004.
20. El Maazouzi, L., P. Colantonio, A. Mediavilla, and F. Giannini, "A highly efficient PA design for WiMAX applications: Theory and experiment," International Journal of RF and Microwave Computer-Aided Engineering, 2010.
21. Carvalho, N. B. and J. C. Pedro, "Large- and small-signal IMD behaviour of microwave power amplifiers," IEEE Transactions on Microwave Theory and Techniques, Vol. 47, No. 12, 2364-2374, Dec. 1999.
22. Chang, C.-P., W.-C. Chien, C.-C. Su, and Y.-H. Wang, "Linearity improvement of cascade CMOS LNA using diode connected NMOS transistor," Progress In Electromagnetics Research C, Vol. 17, 29-38, 2010.