Under The Digital Intermediate Frequency Digital Frequency Converter Based On Fpga Design And Implementation

The DDC(Digital Down Converter) in Software Radio system can reduce the rate of the flow,and send the low speed data to the DSP devices which can process those data fluently,DDC is the bridge between the ADC and DSP devices,its performance will have great effect on the stability of Software Radio system. The dedieated DDC chips have many advantages, such as the stable performance and the higher proportion of extraetion, but the high price and the weak flexibility can not fully reflect the features of the Software Radio. Field Programmable Gate Array has high throughputshort development cycle and online remodeling,because of these advantages, makes the FPGA in software radio research and development is playing a more and more important role.This paper has design and implement DDC based on FPGA, using a top-down modules design method and setting DDC as the basic unit, realizing the function module and composing module libray. In the specific application, optimize the allocation of various modules to meet the specific requirements of the wireless communication system performance.Compare to the traditional ASIC digital down converter it has better programmability and flexibility, which make it to meet the different needs of the engineering design.This paper first introduces the principle and design of numeric down-transducer including the whole system structure and each module design.Then use the Simulink completion to completed the system design and simulation and verify the correctness of the design in Matlab, then use the Verilog hardware description language to design NCO, extraction filters and other key modules in Quartus II development environment. Finally, we do the simulation and test the whole system, and have the correct results.