Research And Design On Digital Predistortion Technology For Power Amplifier

Power Amplifier is a key components of wireless communication equipment such as BaseStation and Repeater. Because its nonlinear characteristics will directly affect the system’s performance. Before we use constant envelope modulation and narrow-band signal, this kind of nonlinear is not very obvious. But as the wireless communication technology’s development, OFDM and QAM is used because of their high spectrum capacityfactor and high efficiency.As a matter of fact, make the signal with high PAPR .And thus signal may be larger than the saturation zone of the Power Amplifier. caused a result of nonlinear amplification. On the other hand,3G communication systems such as WCDMA CDMA2000 and so on, are putting into use ,making the signals with greater bandwidth ,causing memory effects to the Power Amplifier. Also causing an output terminal with nonlinear amplification.The Power Amplifier’s nonlinear will bring about the deteriorate of the system performance. Therefore, we must take linearization technique to solve this problem.Generally,we use linearization technique such as feedforward, digital predistortion and so on. The digital Predistortion method is better than the others in power consumption , degression and reliability.At the same time, as the rapid development of digital technology, the large amount of calculation brought about by the real-time problems be solved. Therefore, this article focuses on digital predistortion technology principle and realization method.This paper mainly studies the memory of the power amplifier nonlinear characteristics, put forward different amplifier mathematical model, contrast several different behavior model and analysis. According the studying the principle of adaptive filter study out linearization algorithm for power amplifier. And simulation all kinds of adaptive algorithm such as LMS algorithm, improved LMS algorithm , RLS algorithm and QRD-RLS algorithm at the same environment using MATLAB. Through comparative analysis, finally we select QRD - RLS algorithm to realize in hardware implementation for its easy to achieve and better performance.Considering the WCDMA signal with high PAPR,we reduce the factor before predistortion .