Design And Implementation Of Controlled Signal Generator Using FPGA Based On DDS Technology

Signal generator is widely used in various fields,such as the generation of standardized signals or a system clock.T he main parameters of performance are frequency resolution,frequency switching speed,spurious degree and so on.Nowadays the demands for the signal generator from various fields are increasing.However,traditional designs had many shortcomings.For example,low resolutions,narrow bands and so on,which is difficult to meet the needs of application.DDS(direct digital synthesis)technology is an ideal option to solve these problems.The signal source of DDS has many advantages such as high frequency resolutions,low spurious,good stability and short frequency agility time which can achieve various digital and model modulations.Furthermore,its all-digital structure makes the integration improve rapidly,and gets rid of its shortcomings such as complicated frequency synthesis circuit,large volume and high cost.FPGA owns the characteristics like high integration,good versatility,cost-effectiveness,flexible design,convenient programming and achievement of the dynamic reconstruction of the chip which contribute to the fast accomplishm ent of complicated digital system.Since the method of analog phase modulation has poor productivity,debugging inconvenience,inaccurate modulation control and other shortcomings,the use of digital methods to achieve a variety of analog modulation is get ting more and more common.In this paper,we design a signal generator,which is based on AD9851,uses FPGA as its core and a MC8051 as the MCU,and has high integration,flexible design,high frequency resolutions,strong stability,low spurious and fast switching speeds.The output frequencies of this signal generator range from 0HZ to 60 MHZ and the output waveforms can be sine wave,square wave and so on.The frequency resolutions can reach 0.1HZ and the frequency switching speed can reach 5us.Our desig n includes several stages of work including overall design,hardware design,software design,fabrication,performance testing,system simulation,software achievement and model building.The final design of the signal generator has advantages like wide ou tput frequency range,short frequency switching time,pure signal spectrum,high stability and simple and convenient operation.The article focuses on the principle and characteristics of DDS,the achievement through MC80C51 and FPGA,and the description o f C51 controlled program.We focus on the FPGA implementation and experimental verification and make a detailed analysis,including the introduction of the design software Altium Designer,the setup of Quartus II project,the design of the frequency counte r module,the CORE,the control module,the filter module,the CLK module,the data storage module and the design of the top of the waveform generator.Also,the experimental verification and simulation of the module and the system are carried out.