Two signal power level design for shunt-connected type GaN HEMT Doherty power amplifier without a quarter-wave inverter

A 1.9-GHz shunt-connected-type GaN HEMT Doherty power amplifier without a quarter-wave inverting network is designed and fabricated by introducing a two- RF- level circuit design procedure. Matching circuits for the carrier and peaking amplifiers are designed to realize optimum efficiency at low-RF (peaking amplifier off) and high-RF (saturated) signal levels. The compact amplifier achieved a maximum power added efficiency (PAE) higher than 50% at the 310-MHz bandwidth. The maximum PAE at an output power above 30 dBm was higher than 50% within the 1.68–1.99 GHz frequency range. A PAE higher than 40% at a 6-dB back-off from input power achieving maximum PAE was obtained over a wide frequency range of 1.67–1.99 GHz.