Research Of Software Radio Digital Down Converter Technology And Implement Based On FPGA

Software radio is a bran-new design which defines band, modulation and signal waveforms by software. Its core idea is to make the broadband A/D converter as close to the RF antenna enough. But the DSP device can not process high-speed data which come from A/D converter directly. In this paper, aiming at the key issue for software radio, a digital down converter system is designed which can reduce the rate of data flow and make A/D converter and DSP support each other. Owing to the Field Programmable Gate Array FPGA is based on the look up table which can achieve parallel computing, that provides the favorable conditions for digital down converter system that needs a large number of fast computing. At the same time, FPGA integrates a considerable of digital signal processing IP core which significantly can reduce the development cycle.In this paper, single-channel programmable digital down converter software radio system were designed based on FPGA. This system completed the down conversion, extraction and filter, then it reduced the data rate.Firstly, studied the basic theory of software radio in-depth by creating a model in matlab,which include,①Naquist low-pass and band-pass sampling theorem;②established a digital down converter architecture③Reseached the signal processing theory of software radio which included digital signal orthogonal transform theory and multi-rate signal processing theory.Secondly, establishd the digital down converter overall design scheme. Carried out the performance analysis of the CIC filter module, half-band filter module and FIR filter module in MATLAB. Improved their algorithm performance, such as Hogenauer decimation filter, Semi-parallel architecture half-band filter and distributed algorithm FIR filter. Finally, the paper comparied with the algorithm performance which is based on FPGA. Used VerilogHDL language and IP core to achieve the optimum design of various module. Given out the RTL-level diagram and external interface of each module. System was simulated and tested through the Modelsim simulation tool, at same time, was integrated and the verified through calling each module. Paper analyzed the test results of digital down converter system.