Design And Realization Of The Arbitrary Waveform Generator Based On DDS

By combining direct frequency synthesis(DDS), universal serial bus(USB) and virtual instrument effectively, a low cost, portable and extensible arbitrary waveform generator(AWG) based on DDS which supports the plug and play function has been realized. FPGA provides the hardware foundation for the design of AWG and the main contents consist of hardware design, logic design and software design.Firstly, the thesis analyzes the basic principle of DDS and the spectrum characteristics of its output, and then presents the methods of improving the spectrum purity of synthesized signal by increasing available capacity of waveform memory, adjusting frequency control word and introducing jittering technique. Secondly, design of hardware system based on the Cyclone II FPGA chip EP2C5Q208C8 is accomplished. Considering the spectrum characteristics of DDS's output, the dissertation designs two kinds of filters to filter signals unwanted. Besides, the design and simulation of address decoder, shift register, phase accumulator and waveform memory are realized with Quartus II. Finally, the firmware code is designed in the Keil uVision2 environment, and WDM driver for USB device is developed. Moreover, user application program of AWG is realized with LabWindows/CVI. On the operation panel of application program, user can choose conventional waves such as sine wave, square wave, triangle wave, sawtooth wave, white noise ect., or draw waves by hand, and set wave parameters to control AWG generate corresponding waveform automatically, which is much convenient.According to the result of experimentation, the frequency resolution of this AWG can be as low as 47mHz, the highest frequency can reach as high as 50MHz, and the frequency accuracy is better than±0.1%. In addition, the output signal maintains good when 50? load resistance is applied across the ends of AWG, which proves that this AWG has attained the desire of design.