Fpga-based Programmable Function Signal Generator Design

Function Generator is a common signal source which is widely used in electronic measurement and scientific experiment. With the development of modern surveying and modern communication technology, the high stability and high purity signal source is in urgent need. However, the raise of DDS (Direct Digital Frequency Synthesizer) and the development of large-scale programmable logic devices have provided the theoretical basis and technical support for the design and implement of new generational function generator.Firstly, this paper introduced the principle and structure of direct digital frequency synthesis and analyzed the source and suppression methods of frequency noise. Through comparing the scheme which realized this technology, the Altera Corporation's CycloneⅡseries chip EP2C35F672C8 was selected as the core chip. A function generator which can generate sine, triangle, ramp and square waveforms was designed which using hardware described language-VHDL as development language. This paper described the main module of function generator in detail, which including the core module direct digital frequency synthesizer and the external circuit, such as human-computer interaction and D/A conversion module. The corresponding simulation results were also presented.At last the test results of the whole system were presented. Experiments showed that this scheme is practical which using DDS combines with programmable device. The result showed that the designed function generator is of high frequency stability, small size, low power consumption and low cost, etc. It will be the future direct of function generator to adopt this technology.