The Design Of The Software Radio DDC Technology Based On FPGA

Software Radio (SDR, Software Defined Radio) as a highly configurable hardware platform, by way of Software to realize various functions, is the current communication field research hot spot.Under the Digital frequency conversion technology (DDC, Digital Down Converter) as one of the core of the software radio technology, make the A/D sampling of intermediate frequency signal is moved to the baseband, ultimate goal is to complete the signal extraction, the pros and cons of its performance will determine the performance of the software radio system.Based on software radio digital frequency conversion technology research, this article main research includes the following aspects of content:1. Software radio are summarized under the digital frequency conversion technology research background, technical features and research status at home and abroad. Analyzes the digital frequency conversion of the digital signal processing theory, the theory of multi-rate signal processing.2. Under the master digital frequency conversion, on the basis of basic principle, analyzed the Numbers under the method of frequency conversion technology of the key modules, including digital control oscillator (NCO, numerically controlled oscillator) and integral Comb (CIC, Cascaded Integrator Comb) filter and Half Band filter (HB, Half Band), and the Finite length unit Impulse Response (FIR, Finite Impulse moisturiser Response) filter filter consisting of a group.3.1. The use of FPGA completed under the digital frequency conversion module design, through the design concept of modeling in Altera company in DSP builder system level design tools for digital downconverter module has carried on the detailed design, first of all, based on the idea of CORDIC algorithm to design a digital oscillator, simple is realized by using Altera company provides IP CORE, high frequency resolution at the same time.On chip multiplier to play the role of a mixer, actually on the hardware implementation is simple.By adopting FDAtool Matlab toolbox and IP core call in digital filter design, digital sampling filter with CIC filter and half band filter cascade form, by adopting the distributed algorithm to implement FIR shaping filter.Finally, the various modules in the system level simulation test, the test show that each module can work normally, meet the design requirements.By using FPGA to realize the key technologies of software radio, digital frequency conversion, based on the modeling of the design concept, can be realized according to the requirements of different systems to implement the digital frequency conversion function, under the double increase development efficiency and reduce the development difficulty.Therefore use FPGA to realize digital down-conversion has practical significance and research value.