Lookup table based digital predistortion algorithm and system simulation
|Course||Communication and Information System|
|Keywords||Linearization Digital predistortion Look-up table (LUT) LMS algorithm M-QAM modulation OFDM|
In Europe, the third generation mobile communication (3G) has been slowly integrated into people's lives, China's third-generation 3G mobile communications has also just around the corner. The third generation mobile communication system needs to support a large variety of business types, allowing users to any place, any time communicate to any person, which requires network transmission must possess excellent structure and a larger amount of data transfer. As a result, the new broadband transmission technology (such as OFDM, WCDMA, etc.) and high spectral efficiency modulation methods (such as QPSK, M-QAM, etc.) are gaining more and more widely used. But these based on non-constant envelope modulation multi-carrier and multi-channel digital transmission technology for RF power amplifiers with high linearity requirements, through nonlinear RF system will generate a large number of intermodulation distortion components, the formation of adjacent channel interference . To solve this problem, we usually use linearization method for correcting the distortion signal. Digital pre-distortion technology because of its high precision, adaptability, implementation is relatively simple, as all the best cost linearization technique a linearization techniques. This paper focuses on non-linear power amplifier predistortion algorithm is studied and proposed a new improved method and an improved algorithm for system simulation. Its main tasks are: (1) the nonlinear system is analyzed, for the commonly used linear methods are analyzed and compared, describes the main technical indicators amplifier. Analysis of several common amplifier mathematical model, and an intuitive way gives a framework for drawing various models. Starting from the algorithm for adaptive digital predistortion scheme for analysis. Major technical and lookup table for the polynomial method adaptive digital predistortion algorithm analysis. Focuses on the LMS, RLS and discrete algorithms such as Newton iteration method to solve the resulting nonlinear amplifier amplitude and phase distortion. (2) the use of the proposed improvements ADS lookup table predistortion system simulation, the tube is used in Motorola's MRF21125, the amplifier's operating frequency is 2.14Ghz. (3) use of matlab software lookup table proposed improved methods for 16-QAM ,64-QAM modulated signal pre-distortion simulation, and on this basis, and QAM modulation for a WCDMA signal pre-distortion processing and simulation, and and do not use pre-distortion and other relevant after using pre-distortion efficiency compared to the simulation. (4) the use of matlab software lookup table in the proposed method is based on the number of carriers is 128, the SNR is 20dB, FFT length 128 of the OFDM system simulation. And other pre-distortion method of simulation results were compared to verify the feasibility of this design scheme to obtain the desired results.