Virtual Arbitrary Waveform Generator Based On Dds Technology

Waveform generator is a kind of electronic instrument, which is commonly used in measurements. The traditional waveform generators are made up of discrete components or analog integrated circuits, so it is hard to debug and control. What is more serious is that the traditional waveform generators only can generate some regular waveforms. In the fields such as modern electronic measurements and automatic controls, it is required that waveform generators can generate more complicated, even arbitrary waveforms in order to satisfy the requirements of various tests and experiments. And then the arbitrary waveform generators emerge as the times require.In order to solve many shortcomings and enhance the flexibility of the traditional waveform generators, this dissertation presents the software and hardware design scheme of the virtual arbitrary waveform generator, which is based on the analysis of direct digital frequency synthesis (DDS) and virtual instrument technology. The whole instrument is partitioned into three parts: Field Programmable Gate Array (FPGA) device, peripheral hardware circuits and upper computer software.The fundamental principle and output spectrum properties of DDS is analyzed, and the spurious distributing rules are given. Based on the spectrum analysis of DDS, this paper introduces some spur reduction methods. A deep study of the spectrum characteristics of spurs brought by phase truncation is discussed by using Fourier transform, and then simulations are performed to validate the results using Matlab.With the significant advantages such as fine frequency resolution, fast frequency switching and good spectral purity of DDS, The desired waveforms are synthesized by DDS technology in this thesis. The realization of DDS depends on high speed and high performance digital devices, so the combination of FPGA device and DDS technology is adopted. The design scheme of FPGA is described in detail, and the optimized design of the key technology is specified. Consequently the digital circuits of this system are accomplished. In addition, the peripheral hardware circuits such as amplitude controller, digital-to-analog converter and low-pass filters are designed for obtaining the analog signals. Eventually the hardware platform is established.The upper computer software is developed under Visual C++6.0. According to program flow diagram, the virtual panel and driver has been designed to help control the hardware circuits at real time. In the software design, the virtual panel is very important, because it can not only generate data and display the waveforms, but also implement a communication between computer and the hardware circuits.Some experiments are performed to test the functions of virtual arbitrary waveform generator. The results of these tests show that the scheme presented meets the anticipative performance requirements.