Design And Realization Of Virtual Signal Generator Based On USB2.0

This thesis originates from the project titled "System Research of Virtual Instruments Based on USB"supported by Xi'an Municipal Science and Technology Commission. Virtual instrument is a user self-defined test and measurement scheme based on PC, which shows a good performance and a powerful expansibility, allows a relative short development period, and exhibits an excellent integration capacity. By combining USB, virtual instrument, and DDS effectively, the thesis design and realize virtual instrument signal generator based on USB2.0. The main contents consist of hardware and software design, timing design and DDS analysis, and are outlined as follows.The thesis systematically analyzes the principle of USB2.0 and the fundamental theory of DDS, and presents the theory instructions for design and realization of virtual signal generator. Upon the analysis of signal generator, a new type of signal generator scheme by combing USB, virtual instruments, and DDS technology is then proposed. Next, the design of virtual signal generator is presented from both the soft and hardware implementation aspects, and the driver for the peripheral equipments of USB and the application programs are realized. Furthermore, the DDS algorithm and the Frequency Segmentation Method (FSM) are analyzed, and the DDS and the FSM function modules are designed and realized in an FPGA chip. The timing simulation of DDS module is conducted with Quartus II 4.1 which shows that the design satisfies the system requirements. Finally, the analysis of the flaws of the virtual signal generator and the performance of actual waves are made and some corresponding improvements are suggested. The virtual signal generator can generate various kinds of waves, such as the square wave, the sine wave, the white noise, the modulated wave, and so on. The frequency resolution reaches as high as 10^-3Hz. The proposed waveform generator features in low distortion, a wide frequency range, and a high frequency resolution, a quick frequency conversion speed, continuous phase during frequency conversion, easy for expansion, and whole digitization advantageous for integration.