Design Of Data Processor Of 4GSPS Arbitrary Waveform Generator

As a kind of measurement instrument,arbitrary waveform generator(AWG),which provides complex stimulation signal,plays an important role in electronic measurement field.Direct digital synthesizer(DDS)is the core of AWG,which consists of data processor and data generator.Data processor in DDS is used to convert the waveform data fed by data generator to analog version,and it is also used to formate the waveform data to satisfy the requirement of digital-to-analog converter.This thesis is based on the data processor of arbitrary waveform generator waveform,analysis of waveform synthesis theory.According to the features of devices and interfaces in circuit,the data processor is designed to realize no-distorted waveform signal convertion from digital to analog version and some specified functions.The main contents of the thesis are as follows:1.The design of data processor scheme.The architecture and output data format of data generator were analyzed to get the requirement of data processor.According to the requirement,data processor was divided into interface unit,data process unit and digital to analog convertion unit.The interface unit,which lied between the data look-up table and the data process unit,was used to buffer the data fed by the data generator and adjust the data rate.The data process unit dealed with the data fed by the interface unit and output the data that met the format requirements of DAC.The digital to analog convertion unit converted the digital waveform version to analog waveform version.2.The design of data interface unit.To solve the problem that the output of data generator is not uniform,an asynchronous FIFO is used as a buffer to realize uniform output of waveform data.According to the problem that the output data rate does not match with the required data rate of digital to analog convertion unit,FIFO capacity monitoring signal for data generator is designed to ensure that FIFO is not overflowed.3.The design of data processor unit.Aimed at the problem that the system can not generate sampling rate at 10 MSPS due to the limitation of low speed of devices,the method,which reduces the read speed of waveform data and broadens the width of waveform data,is used to realize equivalent sampling rate.According to the variable offset index of waveform,postponing the FIFO output enable signal combined with a shift register is used to realize large range and high resolution offset of waveform data.Through the parallel to string conversion techique and data mapping technique,the access of data is realized from data interface unit to digital to analog convertion unit with order adjustment and the width transform from the 512 bit to 64 bit.4.The design of digital to analog convertion unit.According to the requirements of index,the MAX19693 high speed Digital Analog Converter(DAC)produced by MAXIM company is used to meet the highest sampling rate of 4GSPS digital to analog conversion requirement,alonging with the clock circuit,output interface circuit.The variable reference voltage circuit is designed to meet the requirement of precision adjustment of output signal amplitude.And the reference resistance is adjusted according to the purity of output signal waveform.The relationship between full output current of DAC and purity of sinusoidal waveform is studied,and an appropriate reference current is chosen to meet the harmonic and non harmonic distortion requirements of output.After debugging with data generator,the results shown that the design of data processor module can convert the waveform data fed by data generator to analog output wanted.The data processor has sampling rate of 10MSPS-4GSPS,output frequency range of 10 k Hz-1.5GHz,waveform offset resolution of 8points.It can be used to provide high performence for complex waveform,and the technique has reached a advantageous domestic level.