Hybrid Load-Modulated Double-Balanced Amplifier (H-LMDBA) with Four-Way Load Modulation and >15-dB Power Back-off Range

In this work, we present a new architecture of Hybrid Load-Modulated Double-Balanced Amplifier (H-LMDBA) featuring four-way load modulation and large dynamic power range. By appropriately biasing the four sub-amplifiers in balanced control amplifier (CA1, CA2 as carrier, primary peaking) and balanced peaking amplifier (BA1, BA2 as secondary, third peaking), a hybrid load modulation mode with four-way modulation can be realized. To demonstrate the concept, a H-LMDBA prototype is designed with GaN devices and branch-line hybrid quadrature couplers operating at 2.1 GHz. Measurement results show that the H-LMDBA prototype achieves an efficiency of 65.2% at peak power and 51.5% at 15.4-dB output back-off (OBO) under the matched load. In modulated evaluation using a 1024QAM OFDM signal with 20-MHz modulation bandwidth and > 13-dB PAPR. Under matched condition, an average efficiency of ACPR of 50.2% is measured at an average power of 29.1 dBm. In contrast to multi-way Doherty power amplifiers (PAs), this novel PA topology provides an extended power back-off range and enhanced efficiency without significantly increasing the system complexity.