Design of Unsymmetrical Doherty Power Amplifier for 460MHz LTE-Advanced Applications

Abstract

Abstract-An unsymmetrical Doherty power amplifier (DPA) at 460MHz is presented in this paper. The carrier and peaking amplifier of the DPA, which base on two equal-sized devices, are matched with different networks to mitigate the performance degradation caused by the limited load modulation. Measured with continuous wave (CW), the unsymmetrical DPA saturates at an output power of 49.2dBm and achieves a drain efficiency of 51% at 6dB back-off. Using a one-carrier long term evolution advanced (LTE-Advanced) signal with 20MHz bandwidth, the unsymmetrical DPA exhibits a drain efficiency of 48.7% at an average output power of 42.1dBm, along with adjacent channel leakage ratio (ACLR) of -34.1dBc and -53.3dBc before and after digital predistortion (DPD), respectively.

Simulation of Four-Stage Doherty Power Amplifier Structure

“…However for the traditional two-way doherty,its high efficiency of the dynamic range is only 6dB, to have a more peak are better than the signal, the efficiency of the performance is limited. In order to further improve the efficiency of the Doherty, use of the structure are: asymmetric structure [1] and more ways structure [2]. Among them, though the asymmetric structure can expand the scope of high efficiency, its efficiency in the two peaks between apparent drop; And more ways structure not only can expand efficiency range, and but also have multiple efficiency peaks, with higher efficiency.…”