A Broadband Doherty-Like Load-Modulated Balanced Amplifier With an Optimized Impedance Transformation Ratio in InGaP/GaAs HBT Process for Handset Applications

Abstract

This letter presents a design methodology for implementing broadband load-modulated balanced amplifier (LMBA) for handset applications. It is evaluated which architecture, Doherty-like LMBA (DL-LMBA) or pseudo-Doherty LMBA (PD-LMBA), is more suitable for InGaP/GaAs HBT power amplifier (PA). The impedance transformation ratio (ITR) is optimized through an analysis of correlation between the coupler impedance (Z(0)) and matching network (MN). A prototype LMBA attains measured saturation power (P-SAT), collector efficiency (CE), and 6-dB output power back-off (OBO) CE of over 33.2 dBm, 45.2%, and 42.0%, respectively, in the range of 3.2-5.0 GHz. The LMBA is also evaluated by 5G NR FR1 100-MHz QPSK CP-OFDM with 9.5-dB peak-to-average power ratio (PAPR), achieving 26.6-dBm average output power (P-avg) with 37.7% average CE (CEavg) at an adjacent channel leakage ratio (ACLR) of -33 dBc.