Research On Enbedded Progrmmable Swept Signal Generator Module

With the global commercial era of 5G and the large-scale application of embedded technology,electronic measuring instruments are moving toward the direction of intelligence,miniaturization and modularization.As the most basic electronic instrument,signal generators play an important role in the fields of production,research,measurement and control,communications,etc.In order to effectively test the operating conditions of the embedded system,it is required to design a swept signal generator in the system.However,the existing swept signal generators can not meet the requirement.Therefore,a communication protocol based on Modbus standard is proposed,an embedded programmable swept signal generator module with standard communication interface is developed.Moreover,saving time and costs,and reducing the requirements for developers.The main research contents are as follows:(1)Spectrum distribution characteristics of Direct Digital Synthesizer(DDS)output signal are studied,and the index requirements of embedded programmable swept signal generator module are defined.Meanwhile,DDS signal synthesizer model is established,and its method for the modeling is analyzed.The impact that the filter has on output signal is analyzed,which lays the foundation for the selection of the filter.(2)A standard communication protocol is developed,so the embedded system has a great extensibility and flexibility.According to the expected performance index of the system,the communication protocol for this research is developed,and it combines with Modbus communication protocol and system parameter setting requirements.(3)Setting up parameters by the touch screen is achieved.Based on the user's habits and EMWIN graphical interface libraries,human-machine interaction interface is designed.Furthermore,users can choose swept signal generator mode and set up parameters on the touch screen.(4)The technical index and performance of the designed embedded programmable swept signal generator module are tested.According to the experimental results,the above module is easily installed in the embedded system with the developed communication protocol and standard communication interfaces.The module is featured by five modes,including Single tone,Ramped FSK,FSK,BPSK and Chirp.The module outputs sine signal with maximum frequency of 105MHz and maximum amplitude of 500m V.Meanwhile,it outputs square signal with maximum of frequency of 10MHz and amplitude of 3.6V.Moreover,the phase noise is-103.78d Bc/Hz,the stray is-54.19d Bc,and the frequency stability is up to10^-4.Consequently,the experimental test shows that the swept signal generator reaches the expected index with stable performance,which meets the system's technical requirements.