Study And Design Of Broadband High Efficient GaN Doherty Power Amplifier

Gallium nitride(GaN),as a wide bandgap semiconductor,can withstand higher operating voltages,higher power density and operating temperature when used in power amplifier design.For a given power level,GaN-based power amplifiers have the advantages of small size and good frequency characteristics,and are widely used in communication base stations.With the continuous development of wireless communication systems,more data needs to be transmitted per unit time,the peak-to-average power ratio of RF signals continues to increase,and the efficiency of GaN-based power amplifiers continues to decrease.Continuous innovation in circuit topology is required to meet challenges.Doherty power amplifier is one of the most promising methods to improve the efficiency in the output power back-off zone,and it has become a current research hotspot.In order to solve the problem that a large peak-to-average power ratio signal reduces the efficiency of the power amplifier,this thesis first optimizes the single-channel GaN power amplifier to improve the efficiency of its power back-off region,and then combines the asymmetric structure,load modulation network optimization and reverse input Power and other technologies,designed an improved broadband high-efficiency third-order Doherty power amplifier.The power amplifier includes three non-uniform power dividers,an input matching network,a bias circuit,a load modulation network module and a power tube.In the design process of the third-order Doherty power amplifier,for the single-channel power amplifier,the second harmonic control and the input impedance matching at the fallback power point are used to increase the efficiency of the power fallback zone by 11%;for the thirdorder Doherty The bandwidth of the quarter-wave impedance inverter in the power amplifier is narrowed by the maximum impedance conversion ratio of 16.The asymmetric structure and optimized load modulation network are proposed to reduce the maximum impedance conversion ratio to 3,thereby increasing the bandwidth;Aiming at the low signal gain and backoff power efficiency of the Doherty power amplifier caused by the work of the main power amplifier when low-power signal input is too low,a reverse input power technology is proposed to increase the power input to the main power amplifier,thereby increasing Back off power efficiency and gain.Based on the 0.25?m GaN process,a single-channel GaN power amplifier and a thirdorder Doherty power amplifier are designed.The joint simulation results of the circuit layout show that when the designed third-order Doherty power amplifier works at 4.3-5GHz(Fractional bandwidth 15.1%),the saturated output power is 40.5-42.7d Bm,the gain is 5.2-6.6d B,and the power added efficiency is at saturation.It is 33-40.3%,39-43.8% at the power back-off of 6d B,and 32-37.7% at the power back-off of 9d B.Compared with related literature,it has certain advantages of broadband and high efficiency in the C-band GaN Doherty power amplifier chip.