The Design Of The Hardware Moduleof Standard Distortion Signal Generator

The standard distortion signal generator is a device that can be used for the Verification of the distortion tester.It can generate the point frequency signal or the distortion signal required in the Verification.It plays an important role in the development,production,Verification and maintenance of modern communication equipment.The role.The standard distortion signal generator developed in this project can generate standard point frequency signals and distortion signals,has extremely low background distortion,and has the advantages of wide frequency coverage,high frequency accuracy and high resolution compared with traditional products.This article focuses on the above characteristics,and has made an in-depth study on the waveform synthesis scheme,analog channel scheme and hardware implementation structure.The main research contents of this article include:1.Design of waveform synthesis circuit.By comparing and analyzing the characteristics of Various waveform synthesis schemes,combined with project indicators,the waveform synthesis technology with DDS technology as the project was determined,and the waveform synthesis was realized with "FPGA+DAC" as the main structure.In order to meet the-110 dB background distortion index requirements,ADI's 20-bit DAC AD5791 was selected as the project's waveform DAC.At the same time,in order to reduce the impact of environmental noise on the system,an isolation circuit is designed between the FPGA and the DAC.2.Design of analog channel circuit.According to the characteristics of the DDS output spectrum,it is determined to filter the image frequency in a piecewise filtering manner.During the design,by comparing the noise characteristics of different amplifiers in different frequency bands,a low-noise operational amplifier is selected;"coarse adjustment + fine adjustment" is used The structure of the amplitude adjustment circuit has been completed,the output amplitude range reaches 0.316mV?1V,and the amplitude resolution reaches 0.001mV;according to the power supply Voltage requirements of each module,the linear regulator is the main device,and each chip should be noted when designing The decoupling of the power supply end completes the design of the power supply module.3.FPGA logic design.Through the decoding module,complete the communication between the FPGA and the host computer,and convert and decode the waveform sample data and control signals;by calling the IP core,the waveform lookup table and phase accumulator functions are realized,and finally completed by the finite state machine The final output of waveform data and control signals.4.Testing and Verification.Built a hardware test platform for testing the design,and tested the main functions and indicators,including the background distortion of the output waveform,distortion resolution,distortion accuracy,frequency resolution,output level step To wait.The analysis of the test results Verifies the rationality and feasibility of the hardware circuit design of the distorted signal generator in this paper.In the end,this paper implements the hardware circuit module for the "standard distortion signal generator",and realizes the generation function of the distortion signal with low background distortion and the standard point frequency signal,covering the frequency range of 5Hz ?200 kHz,the frequency resolution is 1Hz,and the frequency is accurate The degree is ±0.01%,the distortion degree setting range is-100dB?0dB,the background distortion degree is better than-110dB(5Hz?20kHz bandwidth),with program control function,which can meet the Verification requirements of the distortion tester.