Research And Realization Of A High Efficient Dual-band Doherty Power Amplifier

With the rapid development of wireless communication technology,the traditional single frequency communication system can't afford the requirement gradually.In order to realize miniaturization,increase flexibility and reduce the cost,system of dual-band or multiband is born at the right time.Moreover,modern wireless communication system needs to support high information transmission rate.It brings up non-constant envelope modulation and frequency division multiplexing mode,which turns out a high peak-to-average power ratio(PAPR).It is urgent to be solved how to ensure the linearity as well as improve the efficiency of power amplifier.This paper achiveves the research and realization of the high-efficiency dual-band Doherty power amplifier.The major contribution includes:1)Study how to simply the process of dual-band impedance matching based on Smith chart.The presented transformer is composed of three sections.To transform two arbitrary complex impedances to the desired real impedance,we transform the complex impedances to a pair of conjugate complex impedances firstly.Then,we apply the graphical method to transform the pair of conjugate complex impedances to the same real impedance intuitively.Finally,we match the real impedance to the desired impedance.The approach reduces the difficulty of calculation,makes matching results more clear.2)Do the analysis and validation of the improved combiner of dual-band Doherty power amplifier.Both the carrier and peak amplifiers are matched to 70? at the output port.Then the return loss can be calculated as 15.6dB when the low power is given and 15.1 dB when the high power is given.The proposed structure provides better performance at low input power and maintaining good performance at high input power levels.Furthermore,the improved dual-band combiner simplifies the DPA because of its easier structure.3)Design and implement a concurrent dual-band Doherty power amplifier operating at 2.02GHz and 2.63GHz.For a continuous-wave(CW)output power of 20 W,the measured peak drain efficiency(DE)of the DPA is 62.1%and 71.4%at 2.02 and 2.63 GHz,respectively.Furthermore,the DPA achieves a DE of 49.1%with an output power of 36.9 dBm at 2.02GHz,and a DE of 51.3%with an output power of 37.6 dBm at 2.63GHz at 7dB output power back-of(OBO)from the saturated ouput power.