Digital Down Convert Designed Based On FPGA

Nowadays, in the field of wireless communication, because of limit by sample speedof A/D and processing speed of DSP (digital signal processor), RF signal is transferred tointermeditaed frequency signal, including mixer, decimation, filter and the processed afterdigital down conversion, high-speed signal is switched to low-speed signal, and thenprocessed by DSP. And so Digital Down Conversion play an important role in the software radio system.The artilce on the knowledge of software radio and digital signal processing theory,analysis of the DDC based on the FPGA, and separate the DDC system into parting ofmodules. The algorithms which are applied in the design are compared with each others tomake sure the efficient methods. Using MATLAB and FPGA, the main critieal modulesincluding NCO, CIC Filter, HB Filter and FIR Filter have been implemented, synthesizedand simulated. The article mainly includes these aspects:Making a detailed exposition of the basic theory of software defined radio, includingthe sampling theory, digital filter theory;The article argues deeply the main algorithms used in Digital Down Conberter design,such as: CORDIC algorithm, the CIC filter, the Half-Band filter, Frequency responsemasking technique;This paper separate the DDC system into parts of modules by the function, and make adeeply discussed about the digital down conversion algorithms;Simulation analysis and design on the main modules of the Digital Down Convertusing MATLAB and FPGA;Using FPGA device (EP2C70F672I8) to complete each module of DDC system,realized the narrow-band signal which the extraction obtains from the input wide bandhigh speed signal, make it down to the digital zero intermediate frequency signal, andreduction the data speed, realize the function of DDC and take the simulation and resultanalysis.