The research of defected ground structure application in Doherty power amplifier

The improvement of linearity and efficiency of power amplifier becomes the research focus in the wireless communication. Lots of new methods are proposed successively to realize high linearity and high efficiency, but most of them are implemented with active style and it is complex to implement. The defected ground structure (DGS) in transmission line can form frequency cutoff feature on a specific frequency band. The paper applies the character to Doherty power amplifier structure and improves the gain and linearity of Doherty power amplifier. The experiment proves that the defected ground method is simple and it is easy to implement. The Doherty amplifier is implemented using two freescale MRF6S21050 with output peak power 50 W. The Doherty amplifier delivers an excellent efficiency of 41% with an acceptable linearity of 31dBc at an average output power of 45 dBm. Moreover, the amplifier can provide the high linearity performance of 46 dBc using the digital baseband predistortion technique.