Efficient Rf Power Amplifier Digital Pre-distortion Of Key Technologies

RF power amplifiers is a indispensable module in modern communication systems, its inherent nonlinear characteristics would lead to signal distortion and adjacent channel interference. OFDM modulation scheme, high-QAM modulated signal has a PAPR, on the one hand, the RF power amplifier need to ensure the accuracy of the signal amplification, work in the linear region, back-off work; the other hand, back-off work causes the amplifier reduce its efficiency. The current common RF power amplifier is only about 10% efficiency. Not only caused a lot of waste of resources, but also serious interference with adjacent channel communications.In order to improve power amplifier efficiency, Doherty structure, envelope tracking RF power amplifier has been extensive attention and research, but they have serious nonlinear distortion. In order to improve the linearity, power amplifiers have been proposed linearization techniques, digital predistortion.This article first reviews the development of power amplifier linearization technology history. Then we compared the advantages and disadvantages of several linearization techniques. Early linearization techniques mainly use analog ways. With the modern digital signal processing devices progresses, the digital pre-distortion control adjustable for good, flexible algorithm to achieve, low cost and many other advantages, has become the prevalence way of power amplifier linearization techniques.In this article, key technology of digital predistortion were analyzed and simulated. RF power amplifiers on the characteristics of the study with the model, the model identification algorithm analysis and simulation, and simulation the problems encountered in the practical, analyze the impact on performance. Then, with simulate as a guide and DSP, FPGA and other hardware platform, using top to the bottom ideas to design the module. We show the implementation of digital predistortion function modules and algorithm processing.Finally, build the test platform, combined with CFR technology, Doherty power amplifier, digital predistortion implementations were tested and analyzed. The results show that: the key indicators ACLR is improvement up to 25dB under the conditions of TD-SCDMA signal which input after the PAPR is 6.5dB by CFR. The efficiency of Doherty power amplifier is up to 42% with digital pre-distortion. The indicators are meet the design requirements.These results validate the effectiveness and necessity of the technology of digital predistortion in efficiency RF power amplifier, which has important reference value to base station RRU design.