Analysis and Design of Power Amplifier Using Parallel-Combined Multisegment Transformer

Abstract

This letter presents a highly efficient power amplifier (PA) using a parallel-combined vertical multisegment transformer for 5G new radio (NR) applications operating in bands n257 and n258, in a 65-nm bulk CMOS process. A multisegment transformer facilitates a lower provided input impedance than a conventional transformer, enabling the PA to achieve a higher output power. The vertical multisegment transformer also offers lower insertion loss than the conventional transformer, owing to its high coupling factor. In addition, this work demonstrates that utilizing the compact parallel T-line with vertical multisegment transformers, a low-loss characteristic can be achieved by providing an appropriately low input impedance for high output power. To achieve high efficiency in the low-power (LP) region, the PA operates in dual-mode by applying discrete power control. The PA achieves 24.87-dBm saturated output power with 40.27% peak power-added efficiency (PAE) at 27 GHz. Furthermore, it achieves average output powers of 17.6 and 13.8 dBm with average PAEs of 14.02% and 12.31% in the high- and LP modes, respectively, using 800 Msym/s of 5G OFDM using 64-QAM with −25 dB error vector magnitude.