Design And Research On The DDS System Based On FPGA

The technology of Frequency Synthesis, which consist of Direct Synthesis, Phase-locked Synthesis and Direct Digital Synthesis is widely used in theory of communication, aeronautics and instrument, etc. By using the DDS system, we can obtain signals with high definition infrequency and with sequential phase.The system realized this time which is achieved by FPGA is a DDS system that has the function of digitized frequency modulation of analog signals.DDS is a method that can transform the digitized signals into analog signals by means of DAC. With the help of the high-speed ROM which is used as a look-up-table, the sin-waveforms or other waveforms can be obtained by using the high-speed DAC. The common DDS is composed of three part. The Phase Adder, which accomplish the accumulation of the phase; The Phase Code-Amplitude Code Transformer, which is realized by ROM; The DAC, which transforms the digital signals into analogy signals.According to the design parameters, the paper has undergone the DDS system analysis and designs, including the design of DDS system block-diagram, the design of phase-controlling word and frequency-controlling word, and the design of software and hardware. The keystone rests with improving the design, including the design of the controlling system(frequency-controllor and original phase-contrllor),addressing system(phase accumulator and data memorizer) and conversion system(D/A converter and filter), presents the VHDL fountainhead program of Direct Digital Synthesizer, using the EPF10K20TC144-4 chip of the FPGA chip which belongs to the ALTERA corporation's FLEX10K series.