Research And Design Of Gan High Efficiency Doherty Power Amplifier

With the application of new mobile telecommunication technologies such as OFDM and MIMO, wireless telecommunication system has been developed toward broadband, high efficiency and high power capacity. At present, the application of multi-carrier techniques and different kinds of modulations has improved the peak-to-average power ratio of signals, with the large scale application of such high peak-to-average power ratio signals, how to improve efficiency of RF power amplifier at back-off circumstance has become a hot issue in today’s research, it is widely accepted that Doherty power amplifier technique is an effective method of improving back-off efficiency of power amplifier.Based on Doherty technique and third generation semiconductor material GaN power transistor, the traditional GaN Doherty power amplifier and the GaN Doherty power amplifier using CRLH-TL are analysed, designed and made in this paper. The major work and achievement of this paper includes:(1) Analyse the theory of Doherty technology, design a simplified series transmission lines matching network which is able to reduce the complication of the schematic and do not need tune the real circuit.(2) Design a3.4-3.5GHz asymmetrical GaN Doherty power amplifier using traditional λ/4transmission line. At6-dB and9-dB BOP, the DE achieves46%and31.8%, respectively. The adjacent channel power ratio (ACPR) are less than-21.5dBc and-35.3dBc before and after DPD for100MHz LTE-Advanced signal. (3) Introduce composite right/left-handed transmission lines (CRLH-TL) into Doherty power amplifier, design a3.4-3.5GHz asymmetrical GaN Doherty power amplifier using CRLH-TL for linearity improvement. At6-dB and9-dB BOP, the DE achieves40.1%and30%, respectively. The adjacent channel power ratio (ACPR) are less than-25dBc and-40.4dBc before and after DPD for100MHz LTE-Advanced signal. At last, a compare has been made between the traditional GaN Doherty power amplifier and the GaN Doherty power amplifier using CRLH-TLThe proposed two GaN Doherty power amplifiers all have good performance, especially the GaN Doherty power amplifier using CRLH-TL has the ability of improving linearity while maintaining an acceptable efficiency, advantages like good performance, low cost and low complexity make CRLH-TL GaN Doherty power amplifier has a bright application prospect.