Design of Doherty Power Amplifier Based on Bidirectional Traction and Harmonic Suppression

In order to improve the efficiency of power amplifier(PA), a symmetric Doherty power amplifier (SDPA) based on bidirectional traction and harmonic suppression is proposed. On the basis of the classic DPA, the structure first uses the multi-harmonic bidirectional traction technology to obtain the actual optimum impedance of the power amplifier. Then the two and three harmonic of the main and auxiliary power amplifier are suppressed, and the coincidence of the leakage voltage and current is reduced. Finally, the power distribution of the main and auxiliary power amplifiers is adjusted by adding compensation lines, so that the amplifier can get the maximum efficiency. In order to verify the correctness of the harmonic suppression theory and the bidirectional traction technology, a SDPA device applied to 4G base station is designed by using GaN device. The test results show that the small signal gain of SDPA at 2.6 GHz is 12.6 dB, the gain flatness within the 2.5-2.7 GHz band is ±0.75 dB, and the S11 in the frequency band is less than -11. 9 dB. After the digital predistortion (DPD) system is corrected, the adjacent channel leakage rate (ACLR) at the three carrier test is about -45 dBc, the power additional efficiency (PAE) near the peak power point of SDPA is close to 60%, and the PAE at the backdrop point is about 48%. The experimental results verify the feasibility of the design.