Design And Realization Of Digital Predistortion Based On Novel LUT

With the rapid development of communication technology, we tend to need more and more information by wireless communication. However, how to make use of the limited spectrum resource to transfer a large amount of information while ensuring high quality is one of the scientific researchers' focus. To achieve an improved spectral efficiency, some advanced complex modulation schemes(QAM, OFDM) have been developed. But if we want to ensure the quality of signal transmission, we must pay more attention to the whole system's hardware. Power amplifier(PA) is one of the most important parts of communication system, its nonlinearity affect the quality of the whole system badly. Nowadays the methods to improve its linearity are at the cost of sacrificing its own efficiency. So how to improve PA's linearity and maintain its high efficiency is what we are concerned and this paper will utilize digital predistortion(DPD) technology to solve the problem.In this paper, we introduce the sources and measure indexes of PA nonlinearity first. Then we illustrate several ways of modeling PA's behavior model, the principle of predistortion and the most commonly used structures of predistortion. After that, we design our digital predistortion. We select direct lookup-table(LUT)-based learning architecture and we use MP modeling to model the PA. In the process of extracting the PA's parameter, RLS adaptive algorithm and cross correlation time delay algorithm is chosen, the results show the accuracy of our attempt. In the design of novel LUT, we introduce the concept of weighting-factor to make the LUT piecewise-uniformed instead of dividing the whole LUT uniformly. This makes the distribution of LUT more reasonable. What's more, we combine linear interpolation technique with it to reduce the number of LUT greatly. The simulation results show the feasibility of our proposed novel LUT digital predistortion. At last, in order to evaluate our proposed DPD, some measurement are realized on a test branch based on instrument test platform. The test results show the effectiveness of our proposed DPD, the upper and lower bands' ACPR of the main channel can achieve an improvement of 15.54 dB and 18.89 dB, respectively. The novel LUT-based DPD have an excellent performance.