Design And Implementation Of Baseband Digital Predistortion Technology For Radio Frequency Power Amplifier

With the rapid development of Internet business, audio, video and digital communication industry have achieved rapid advancements, and future communication technology has raised high expectations. Wireless broadband communication technology developed rapidly in the communication industry in recent years, and the demand for bandwidth grows gradually, thus lack of band resources is unavoidable. Adopting more efficient modulation technique and data transmission technology can increase the utilization ratio of band resources. However, most of these technologies have the characteristics of high broadband and PAPR(Peak to Average Power Ratio).The power amplifier plays an vital role in wireless communication system, but its inherent nonlinear and memorability can cause in-band distortion and spectrum extension out of band, thus resulting in higher error rate in communication system. In-band distortion can cause distortion of amplitude and phase in input signal, and the spectrum extension out of band mainly reflected in the interference for adjacent channel.With the increase of signal bandwidth, the signal distortion of power amplifier become increasingly serious. In order to decrease the impact of non-linearity and increase the efficiency of the power amplifier, one way is to decrease the PAPR, while the other is to use power amplifier linearization to get high efficiency.The former can guarantee power amplifier linearity, but it causes lower efficiency. Digital Pre-distortion gives a good solution to efficiency and linearity, and it has been widely used for its simple structure which is easy to be realized by HDL(Hardware Description Language).This paper is based on the relevant theory of communication system and analysis of pre-distortion system via digital signal processing. This paper also serves to show the design and implementation of every functional part for the digital pre-distortion system by FPGA+DSP.Firstly, characteristics and common behavior models of power amplifier are discussed in this paper. This paper uses pre-distortion technology to improve the nonlinear and memorability of the power amplifier by analyzing its issues in application and gives the specific schemes.Secondly, This paper gives the design for the various parts of the digital pre-distortion system and verifies their function. The FPGA chip is used to deal with digital signals and the DSP chip is used to realize the algorithm.Finally, functional verification of the pre-distortion system is completed from baseband frequency、medium frequency to radio frequency, and the analysis of the results is also included.