A sequential power amplifier at 3.5 GHz for 5G applications

In this paper, a broadband Sequential Power Amplifier (SPA) is designed and realized for the use in an active MIMO antenna around 3.5 GHz. For that purpose, specifications for the individual components are derived to yield optimum performance of the complete SPA when amplifying a mobile communication signal. In order to meet the size requirements of an active antenna, amplifier modules that include all necessary transformation and stabilization networks inside the package are developed. The SPA achieves a bandwidth of more than 1 GHz (RBW of 28%) and shows a peak drain efficiency of 47% in 8 dB backoff at 3.5 GHz. To transmit a complex signal such as QAM using the SPA, its two inputs have to be driven according to the system's characteristic curve. For the first time, modified constellation diagrams for each input have been derived to transmit a 16-QAM-modulated test signal with 10 MBaud at 3.2 GHz. For the amplification of this signal, the system shows an increase in drain efficiency of 10 %-points compared to a conventional class-B PA.