Design And Implementation Of DDC System Based On Realtime MIMO Platform

What this thesis discussed is the design and implementation of DDC system which serving in MIMO real-time platform, and this system is realized through adopting wide IF signal bandpass sampling technology based on Software radio.MIMO is the major technique in the new generation mobile communications system. The MIMO experiment platform system provides a real physical environment for multiple input multiple output mobile communications system. Through this platform, signal can be transmitted in a real wireless channel, so that researchers can test performance of MIMO communication algorithms and their design well and truly.Digital down converting system is a major part in MIMO platform, and also a key technique in Software Defined Radio.The function of a Digital Down Converter is to convert an intermediate frequency bandpass signal after ADC into a baseband signal through mixing the input signal with the digital orthogonal sin/cos sequence produced by NCO, to decimate the output signal using multi-rate signal processing technology to transform the high data rate to a lower sampling rate which is suitable for baseband DSP processor, and to filter the signal with cascade lowpass filters to improve the performance of the processed signal.In this thesis, we introduce the significance of establishing MIMO platform, technology of Software Defined Radio, model of IF receiver based on the SDR and the current research of DDC. Followed we detailedly introduce the key theories and technologies of DDC-sampling, digital orthogonal mixing, NCO, efficient digital decimation filtering.Then design the intermediate frequency, sampling rate, mixing and decimation scheme of the system, and give the modeling of DDC system based on the MIMO platform adopting wide IF signal bandpass sampling technology. The structure of one channel DDC and the design and simulation of the NCO module, digital mixer, CIC decimation filters, FIR lowpass filters consisted in DDC are discussed detailedly.We use Xilinx system modeling tool-System Generator to realize the FPGA design of DDC. Through downloading the design based on MIMO platform to Xilinx Virtex-II Pro FPGA board, implement software simulation and hardware software co-simulation. The simulation results verify the feasibility of the DDC system. In the end, analysis the resource consumption and timing performance of DDC system.