The Hardware Circuit Design Of Low Spurious Arbitrary Waveform Generator

Arbitrary Waveform Generator(AWG),as a type of signal generation equipment,can generate a variety of standard waveform signals and user-defined waveform signals.It also has the characteristics of fast frequency switching and large bandwidth,so in the signal source Plays a very important role.Compared with the RF signal source,the AWG output signal has a smaller Spurious Free Dynamic Range(SFDR)index,which has become a key factor restricting the further application of the arbitrary waveform generator.This master thesis investigates six SFDR indicators with with a sampling rate of less than 2.5GSPS,and finds that the indicators are all less than 40 d Bc in a 500 MHz bandwidth.Therefore,this paper designs a low-spurious AWG with a 2GSPS sampling rate,and the harmonic SFDR index is greater than 50 d Bc in the 500 MHz output bandwidth.The specific work content is as follows:1.Spurious signal analysis.By analyzing the ideal DDS(Direct Digital Synthesis,DDS)output signal spectrum,it is concluded that the digital to analog converter(DAC)retention characteristic will add the image frequency signal to the output signal spectrum;the device used to realize the DDS structure through analysis The gap between the parameters and the ideal DDS structure parameters,the relationship between the phase truncation error and the amplitude quantization error introduced in the DDS technology and the output signal SFDR index is derived;based on the integrated operational amplifier simulation model,it is obtained that when the AWG output signal frequency is greater than 10 MHz,the amplifier Harmonic distortion caused by nonlinearity is a key factor affecting SFDR indicators.2.Low spurious AWG hardware circuit design.By analyzing the influence of the above four factors on the SFDR index of the low-spurious AWG output signal,it is determined that the phase truncation error and the amplitude quantization error have caused the spurious signal amplitude to be too small and can be ignored.The SFDR index is filtered by a low-pass filter circuit The method of outputting the image frequency signal and harmonic frequency signal in the spectrum is realized,and the SFDR index of the output signal meets the target requirements through MATLAB software simulation and hardware circuit testing;based on the "FPGA+DAC+memory" structure,through the analysis of the low spurious AWG function Indicators and performance indicators,complete the hardware circuit design of the instrument;.3.FPGA logic engineering design.Based on the PCIe bus to realize the communication function between the host computer and the PCB board;based on the data transmission module to solve the conversion from non-uniform memory transmission to uniform transmission;based on the data transmission interface module to achieve the maximum transmission of 32 Gbits of waveform data to the DAC chip;based on AXI4-Lite bus,realizes functions such as clock chip configuration,signal conditioning circuit control and instrument status information readback.The test results show that the output signal capability of the low-spurious AWG is not weaker than the ES1654,Dingyang Technology SDG6052 X and Keysight M9336 A instruments,and the output signal SFDR index is better than the above three instruments,specifically the output signal frequency is within 300 MHz When,the SFDR of the instrument is greater than 65 d Bc;when in the range of 300 MHz to 500 MHz,the SFDR of the instrument is greater than 50 d Bc.The AWG with low spurious output capability can not only apply to more test scenarios,but also improve the overall performance of the system containing AWG equipment.