High Frequency Function Signal Generator Based On DDS

Signal generator is first of the signal chain.It plays a important role when develop or test a communication system.Testing a communication system is impossible without high quality signal generators.Thus,the study of signal generator is practically significant.Direct digital synthesis technology(DDS)is the current synthesis method for the majority of signal generator on the market.DDS is the main program for the signal generators.With the continuous progress of semiconductor technology,many DDS integrated chip performance has been greatly improved and has been more feature-rich,which provides a possibility to simplify the system,improve the integration degree and improve the performance.Also,it reduces the cost of production.Firstly,this design introduces the research background and significance of the subject.Then we summarize the development status of signal generator and integrated DDS chip at home and abroad.On this basis,the design of the existing function signal generator is compared to determine the realization of the function signal generator designed in this project.The design of the function signal generator select ADI's integrated DDS chip-AD9910,which is the main chip of the signal generator,and then use the ST's 32-bit microprocessor-STM32F103RCT6 as a control unit to control the DDS chip and people Machine interface.STM32 collect user's data through the virtual keyboard on the TFTLCD screen and send user's data to display on the TFTLCD screen.At the same time the user's data is sent to the relate registers of the AD9910 chip through the SPI serial communication interface so that we can output the corresponding waveform.As the amplitude of the direct output signal of the AD9910 chip is small and more spurs,so that we process the signal at the output and add a high frequency amplifier and a Chebyshev low-pass filter.The amplitude of the signal is enlarged by a high-frequency amplifier,and the spurious is filtered out through the Chebyshev low-pass filter.At the same time,in order to reduce system noise further and electromagnetic interference(EMI),we separate the digital part with the analog part of the system in the PCB design process,so we ensure the integrity of the system signal effectively.Finally,we assemble and test the system.Through testing,the signal generator conforms to the system design requirements,achieving the design goals of the system,reducing the system cost effectively,improving system performance and working stability.