Design Of Doherty Power Amplifier

As modern wireless communication technology develops, Communication system requires more demanding of power amplifier. Modern wireless communication need to transmit information as much as possible. It needs to have more complex modulation mode, These modulation mode require signal which must have larger dynamic input range, and have much linearity demanding for power amplifier. In the modern modulation technology, such as WCDMA, use unsteady envelope modulation, and have high peak to average power ratio. The power amplifiers, class A and AB, using power back-off scheme are difficult to meet the efficiency requirement under the condition of a high PAR, which cause a huge energy dissipation while producing a lot of heat. What's more, it degrades the system performance and raises the production cost. Therefore, enhancing the efficiency of power amplifier is one of Future directions.In recent years, the study and application of Doherty power amplifier which has simple structure and high efficiency in WCDMA digital repeater becomes a hot spot.This paper aims to design a Doherty power amplifier by the Freescale's LDMOS transistor MRF21030.The power amplifier which has high efficiency and high linearity is used in W-CDMA communication system. Souce-pull and Load-pull technology are used in the design to get the best source impedance and the best load impedance. Set reasonable Doherty power amplifier bias circuit to ensure a suitable quiescent point. To add compensated microstrip lines in the power amplifier output matching network will solve the leakage problem in Doherty power amplifier and improve the efficiency of the Doherty amplifier. Finally, the power amplifier's good performance. is tested through the ADS simulation...