Hybrid Load-Modulated Balanced Amplifier With High Linearity and Extended Dynamic Range

A novel hybrid load modulation (LM) architecture of power amplifier (PA) is presented in this letter, in which three amplifiers are combined through a quadrature coupler in properly defined phase offsets. Together with the well-aligned turning-on sequence, the PA can operate as a Doherty PA (DPA) and load modulated balanced amplifier (LMBA) at different power levels, whose overall behavior is similar to a three-way DPA. This unique hybrid LM mode effectively extends the dynamic power range of efficiency enhancement, which is further compatible with the high-linearity design. This concept is experimentally validated using a GaN-based prototype at 3.56 GHz. The CW measurement shows an efficient PA performance with 49%-63% of efficiency from P_{\mathrm {Max}} to 9-dB back off. Under the modulated evaluation using a 20-MHz LTE signal, an adjacent channel leakage ratio of −37.5 dB is measured together with 45% average efficiency.