Asymmetrical Doherty power amplifiers for LTE-Advanced systems

In this paper, the optimization approach of a wideband and high efficiency asymmetrical Doherty power amplifier (ADPA) for LTE-Advanced systems was presented. The ADPA using the different LDMOS devices and an uneven power divider achieves constant efficiency at more than 6 dB output power back-off. The radial stubs and duplicate supply are utilized in the dc bias network to increase the bandwidth of the ADPA. The carrier amplifier (MRF8S19140) and the peaking amplifier (MRF8S19260) operate at class-AB and class-C respectively. Through ADS optimization design, the power added efficiency (PAE) is 59.064% when the maximum output power reaches 57.1 dBm at 1950MHz. At 8.5dB back-off point, the PAE is 51%. The bandwidth of the ADPA is about 145MHz ranging from 1880MHz to 2025 MHz, maintaining the gain flatness lower than ±0.5dB in small signal mode. The PAE in the whole band basically remains 45% or more for medium power level.