The Design of Direct Digital Frequency Synthesis Based on ROM Lookup Table

The existing direct digital frequency synthesis (DDFS) only can generate one kind of waveform with one read-only memory lookup table (ROM LUT), which cannot provide inphase wave and quadrature wave for global position system(GPS) carrier tracking. A DDFS is designed based on ROM LUT. Using the symmetry of the sine wave and the property that cosine waveform is leading or lagging one fourth period compared with sine waveform , only one fourth of the storage table of sin waveform is needed to develop both the whole sin wave and cosine wave. The pipeline technique is utilized to improve the working speed of the system. Assisted by Quartus II software and very high speed integrated circuit hardware description language(VHDL), a simulation to the designed DDFS is finished with a good result. At last, an error analysis is made to the result of simulation.