The Design Of High Efficiency Power Amplifier MMIC Based On Doherty Architecture

Accompanying the rapid development of mobile communication,communication technology adopts the latest advanced modulation techniques,so as to meet people’s requirements for information communication transmission effectively and efficiently.The power amplifier,the core component of the radio frequency transmission part,plays a vital role in the performance of the whole radio frequency transceiver system.When traditional AB-type power amplifiers experience power back-off,the decreased output voltage will reduce efficiency significantly,which not only causes energy waste,but also increases the cost of heat dissipation design.Featured with high efficiency and a simple design structure during power back-off,Doherty power amplifiers are increasingly popular among high-efficiency power amplifiers.Taking the design of active load traction technology as the foundation,the thesis improves the output circuit matching and designs two high efficiency Doherty power amplifiers that can be applied to communication equipment,including 5G base stations in different scenarios.The symmetrical Doherty power amplifier designed by the 0.15μm Ga As process is capable of effectively improving the efficiency of power back-off by optimizing the output matching circuit of the main power amplifier and removing the rear extension line.The electromagnetic simulation results show that S₁₁ is less than-12d B,S₂₂ is less than-10d B,and the saturated output power reach beyond 27d Bm during the frequency of 27.5GHz～28.5GHz,where the Power Added Efficiency（PAE）is beyond 37%,and the power gain is 9.8d B;when the power back-off reaches 6d B,the PAE can reach beyond 30.5%.The asymmetric Doherty power amplifier designed by the 0.25μm Ga N process improves the traditional Doherty power amplifier structure through the following three aspects:firstly,the asymmetric Doherty power amplifier optimizes the output matching circuit of the main power amplifier and abandoned theλ/4 impedance conversion lines;secondly,the output impedance of the auxiliary power amplifier is replaced by an RC network equivalently,and the phase controlling the output matching circuit is 0 degrees to ensure a high impedance state when turned off;finally,the main amplifier and auxiliary amplifier are directly loaded with a 50Ωload at the junction,and the network is matched after removal.To improve the gain,the drive power amplifier will be added in front of the Doherty power amplifier.The electromagnetic simulation results show that the saturated output power reached beyond 44d Bm,the PAE reached beyond 50%,and the Power gain was about22d B during the 3.3GHz～3.6GHz;however,when the power back-off reached 9d B,the PAE reaches beyond 35%.In terms of the performance of physical testing,there is a certain deviation between the test results and simulation results influenced by process and model deviations,and the frequency of the amplifier shifts from 3.3GHz～3.6GHz to 3.6GHz～3.9GHz.The typical data saturation output power reached 44dBm after measuring,and PAE reached 40%,and reached 34%when power back-off reached 9dB.