Enhanced Dual-Mode Reciprocal Doherty Power Amplifier Using Modified Combining Load and Parameter Sweeping Analysis

This article presents a theoretical analysis and circuit design for an enhanced dual-mode reciprocal Doherty power amplifier (DM-RDPA). To achieve bandwidth enhancement, an improved combining load design strategy is proposed, providing more accurate back-off impedance across a wider target bandwidth. Additionally, a sweeping analysis method is developed to determine optimal design parameters. The enhanced combining load design space of the proposed DM-RDPA is visualized, providing an intuitive view of the appropriate impedance solution space. To validate this enhanced DM-RDPA architecture and the corresponding design analysis method, a prototype PA was designed and fabricated using commercial GaN transistors. The implemented PA achieves two different Doherty operation bands: 0.95-1.9 GHz (66.7% fractional bandwidth) in Mode I and 0.67-0.93 GHz (32.5% fractional bandwidth) in Mode II. Drain efficiency of 47.3%-62.2% and 44.7%-62.1% is obtained by the fabricated DPA at 6 dB back-off in Mode I and Mode II, respectively. When driven by a 20 MHz modulated signal with 8 dB peak to average power ratio (PAPR), the fabricated DPA presents higher than 42% average efficiency in both Mode I and Mode II.