Research On Digital Pre-distortion Technique In OFDM Signals

OFDM technology in its high spectrum efficiency, the advantages of anti-interference ability and has been more and more widely. This article summed up the first systematic analysis of the basic principles of OFDM, characteristics, and from the perspective of the signal that constitutes the OFDM signal sensitive to the reasons for non-linear power amplifier, power amplifier through the commonly used model for analysis of the nonlinear amplifier.The focus of this paper is a digital pre-distortion technology, pre-distortion on the basic principles of technology, the detailed discussion based on the look-up table(LUT) and polynomial based pre-distortion technology. One look-up table based pre-distortion technique described in detail in the form look-up table, address look-up table index, and the methods used often, in the polynomial pre-distortion techniques are given in polynomial pre-distortion of the schematic diagram and a detailed description of its principle. Next on the OFDM system polynomial pre-distortion algorithm is focused on, first of all through the Volterra series model of the power amplifier to improve the model for the purpose of computing have come up with a simplified model of the amplifier, through the power amplifier model polynomial pre-distortion device to draw the model, and then through to the minimum mean square error of the polynomial algorithm and recursive least-squares analysis of the polynomial algorithm of comparison, the last of the recursive least-squares polynomial simulation algorithm and the memory of different depths in different order under the non-linear simulation results are compared and analyzed. Amplifier to verify its effectiveness of non-linear compensation, the effective elimination of the non-linear power amplifier caused by the transmission signal of the amplitude and phase distortion, adjacent channel signal to reduce interference and improve the system bandwidth efficiency.In order to improve the OFDM digital pre-distortion performance of the system, the paper proposed to improve the system a dual-power digital pre-distortion system, and through computer simulation to verify a dual-power digital pre-distortion system can effectively improve system performance, so that the output signal of a more a big gain.