Research And Design Of Doherty Power Amplifier Applied In 5G Communication Band

With the development of modern mobile communication system,the performance of transmitter module in wireless system is more stringent.As the core device of the transmitter,power amplifier requires higher linearity and efficiency.Especially,the new modulation technologies all adopt more complex non-constant envelope modulation mode,which makes the signal peak average relatively high and can reach 6-12dB,so the linearity of power amplifier must meet higher requirements.In order to meet the requirements of linearity and efficiency in wireless communication systems,Doherty technology is widely used.Doherty structure is a technology to improve efficiency in high output back-off Its main advantages are:simple circuit structure,no complex auxiliary structure and configuration,and it has a wider bandwidth.At the same time,the third generation of GaN has many excellent characteristics.The power amplifier based on this material has better performance and can better meet the requirements of wireless communication technology for power amplifier.In order to reduce the size of Doherty power amplifier,the internal matching method is adopt.In this paper,two Doherty power amplifiers with different frequency bands are designed and implemented.One of the power amplifiers is operated in a frequency range of 3.9-4.2 GHz and the input signal is continuous wave.The size of the Doherty power amplifier is only 27.4 mm×30.8 mm.The saturated output power is over 48 dBm.The drain efficiency reaches 55%and above at saturation.When the output power falls back to 6 dB,the drain efficiency reaches more than 50%.The IM3 value of the tester is superior to the balanced class AB power amplifier in the regress area and can reduce 3dBc.The other power amplifier is used in one of 5G communication bands-4.8-5.0GHz.Its input signal is continuous wave.Its size is 16.4mm×17.8mm.Its saturated output power reaches 47dBm.Its drain efficiency at saturation reaches 50%and above.The drain efficiency at the output power back-off point of 6dB reaches 45%.The I M3 value is better than class AB power amplifier in the power back-off region and can reduce nearly 7dBc.