A 24-29.5 GHz Voltage-Combined Doherty Power Amplifier Based on Compact Low-loss Combiner

In this brief, a 24–29.5 GHz millimeter-wave (mm-wave) voltage-combined Doherty power amplifier (DPA) based on compact low-loss combiner is proposed for the fifth-generation (5G) applications. By maximizing the use of parasitic parameters in the circuit, a compact low-loss combiner is proposed to achieve the required impedance transformation with only one additional series capacitor. A detailed design procedure is also introduced in the brief. Based on the proposed combiner, a fully integrated Doherty PA is implemented in 0.13- ${\mu }\text{m}$ SiGe BiCMOS process with a core area of only 0.29 mm2. The DPA achieves a 27% −3-dB small-signal gain fractional bandwidth and a 15.9 dB small signal gain at the center frequency of 27 GHz. The −1-dB Psat bandwidth covers 24–29.5 GHz (20% fractional bandwidth), and the maximum output power is 20.8 dBm ± 0.4 dB. From 24 to 29.5 GHz, the designed DPA provides 23.2% to 28.4% power-added efficiency (PAE) at saturated output power, and 18.3% to 21.9% PAE at 6 dB of output power back-off (OPBO).