Two-Stage Doherty Power Amplifier Using Broadband Interstage Matching Network

This letter presents a broadband interstage network for a two-stage Doherty power amplifier (DPA) with dual-drive amplifiers. The broadband interstage network consists of a load matching network of the drive stage, an input matching network of the main stage, and an optimized length of the transmission line between them. Both the matching networks are designed with simple L-section structure for the reference impedance 50 Omega. Then, the 50- Omega transmission line with an optimized length between them matches the frequency deviations of the two matching networks over a broad frequency band. For verification of the broadband interstage network, a (3.4-3.8)-GHz two-stage DPA was designed and implemented as a hybrid circuit for the sub-6-GHz 5G NR band. The core size of the DPA is 25 x 40 mm, and a drain efficiency of (40.7%-47.0%), power gain of (27.5-27.7) dB, and adjacent-channel leakage power ratio (ACLR) of (-46.4 to -40.4) dBc after digital predistortion (DPD) were obtained at an average output power of 37.5 dBm using the 5G NR signal with a signal bandwidth of 100 MHz and a peakto-average power ratio (PAPR) of 9.3 dB.