| The power amplifier is an important part of the wireless transceiver system,which plays a key role in signal transmission quality.At present,non-constant envelope modulation technology is widely used in 5G communication systems to improve spectrum utilization,resulting in relatively high peak to average power ratio.Therefore,it is required that the efficiency of the power amplifier in the back-off range should maintain high level.The Doherty power amplifier has many advantages such as high back-off efficiency,simple structure,and high cost-effective performance.It has become the mainstream power amplifier architecture for base station systems.This paper will focus on the harmonic control technology to carry out research on the high-efficiency wideband asymmetric Doherty power amplifier with quasiMMIC technology.Firstly,a basic 3.4GHz-3.8GHz class-AB power amplifier is studied and fabricated.The parasitic parameters and package parameters of the transistor are extracted by cold-FET approach.On this basis,the Chebyshev low-pass network is used for output impedance matching.The measurement shows that the saturated output power of the amplifier in the frequency band is about 10 W,the saturation efficiency is 46%,and the linearity is good.Secondly,a 3.4-3.8GHz continuous-mode Doherty power amplifier is designed.in order to control the harmonics better and improve the efficiency,elliptical low-pass matching network is studied and designed on the basis of Chebyshev low-pass matching to design the output matching network of the carrier amplifier.The LC parallel block in the elliptical low-pass network can control the harmonics better,making the carrier amplifier work in the continuous mode in the back-off region and improving the back-off efficiency and bandwidth.A low-pass matching network is used to realize the impedance inversion network.The elliptic low-pass matching network is also used in the peaking amplifier to adjust the second harmonic.The simulation results indicate a saturated output power of 10 W,12d B linear gain and a 55% drain efficiency of 9d B back-off.Finally,a high-gain two-stage 2.3-2.7GHz Doherty power amplifier is studied and fabricated.The influence of drive-stage and power-stage’s parameters on overall PAE(power added efficiency)is analyzed,and then the output matching network is designed with the Ttype inductances and parallel capacitor.An LC parallel network is used to replace the bias inductance of the output matching network to reduce loss.Considering the influence of the noninfinite output impedance of the peaking amplifier,the impedance trace of the carrier amplifier on the intrinsic plane conforms to continuous mode amplifier in back-off region.Simulation results show an 10 W saturation output power,30 d B linear gain,2d B gain flatness,46%power added efficiency at 9d B back-off.The measured results show that the saturated output is 36 d Bm,and the 8d B back-off efficiency is greater than 35%. |
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