Research And Verification On Key Technology For All-digital Transmitter's High Efficiency Linear Power Amplifier

The all-digital transmitter is up-converted in the digital domain,without analog components such as IF filter,phase-locked loop,and mixer.Compared with the conventional wireless transmitter,it has the advantages of high integration,small size,and flexible configuration.As a critical component of the all-digital transmitter,power amplifiers have a decisive influence on the efficiency and linearity of the transmitter.High efficiency and high linearity have always been the goals for power amplifier design.This paper designs a high efficiency,high linearity power amplifier for all-digital transmitters.The main work of this paper is as follows:Firstly,the system summarizes the implementation of all-digital transmitters,the main class of power amplifiers,power amplifier linearization techniques,and the types of amplifiers used in all-digital transmitters.The power amplifier is divided into a traditional power amplifier and a switching power amplifier;the main technologies of the power amplifier linearization are pre-distortion technology and feedforward technology.In order to improve the efficiency and linearity of the all-digital transmitter power amplifier,the Class F power amplifier with higher efficiency is used,and the feedforward technology is combined to improve the linearity of the Class F power amplifier.Secondly,the demand of all-digital transmitter power amplifier is analyzed,the power amplifier index is determined,and the key indicators of power amplifier are analyzed and deduced.The class F power amplifier and feedforward class F power amplifier are designed.The simulation of the Class F power amplifier shows that the power added efficiency is up to 69.1%,the third-order intermodulation suppression is-14 dBc,and the fifth-order intermodulation suppression is-30 dBc.The feedforward technique is used to improve the linearity of the Class F power amplifier.The third-order intermodulation and fifth-order intermodulation suppression are improved by more than 25 dB.Meanwhile,an error negative feedback technique is proposed.The simulation result shows that the error negative feedback technique improves the adjacent channel power ratio(ACPR)of the Class F power amplifier by more than 10 dB.Thirdly,the feedforward Class F power amplifier PCB is implemented,and the experimental test platform is established to measure and verify the key indicators of Class F power amplifier and feedforward Class F power amplifier.In the single tone test,the added efficiency of the Class F power amplifier is 65%;in the two-tone test,the thirdorder intermodulation suppression of the feedforward Class F power amplifier is-41 dBc.Combined with all-digital transmitters,the test results show that the feedforward Class F power amplifier gain is 55 dB,and the feedforward Class F power amplifier efficiency is 28%.Compared with the Class F power amplifier,the feedforward Class F power amplifier adjacent channel power ratio(ACPR)improved by 10 dB.In summary,this paper uses a combination of Class F power amplifier and feedforward technology to design a high efficiency,high linearization power amplifier that can be applied to all digital transmitters.The actual measurement proves that the power amplifier has the characteristics of high efficiency and good linearity,which provides a certain reference for the design of high efficiency and linear power amplifier.