Fpga Implementation Of Mimo-ofdm System Transmitter Key Technologies

Due to its high spectral efficiency and robustness against frequency selective fading, Orthogonal Frequency Division Multiplexing (OFDM) has become a key technique in future wireless communication. The basic principle of OFDM is to divide a wideband frequency channel into several overlapping subchannels and every sub-carrier transmits data in every subchanel. Due to sub-carrier modulation of OFDM based upon calculation of signal constellations and OFDM modulation needing numerous calculations, OFDM transmitter must have a strong capability of calculation and the idea that we use FPGA for completing the task has become a trend.The OFDM modulated signal usually owns high PAPR, which demands a relevant wide linear range for the high power amplifier. Meanwhile, Broadband Characteristics of OFDM signal causes the HPA to generate nonlinear distortion with memory and increases Intersymbol Interference (ISI), so digital predistortion which can reduce the linearity requirement of HPA has become a popular technology in OFDM system transmitter.This thesis derives from some OFDM-MIMO pre-research communication system which adopts the design conception of Software Defined Radio (SDR) and uses the hardware architecture of FPGA plus DSP.This thesis investigates the FPGA implementation of OFDM system transmitter. The main contents include the OFDM symbol modulation, system signal Framing, Digital Up Converter and peripheral interface in FPGA implementation. Finally, the design has passed hardware experimental verification in the environment of Intermediate Frequency direct Interconnection.In the topic of digital predistortor design, this thesis study the indirect learning predistortion algorithm based on Volterra Series and has completed the FPGA design implemention of this kind of predistortor. According to the feature of algorithm in the practical design of circuits, we simplified the design structure of circuits, reduced the data computational complexity and resource consumption greatly in FPGA. In order to verify the design, we construct specific parameters wiener model of High Power Amplifier (HPA). The results of test demostrate that the predistortor can reduce the Intermodulation Distortion (IMD) up to 18dB and prove correctness of designing methods.