Research On Sample Rate Conversion Technique Of All-digital Modem

In this paper,"Research on Sample rate Conversion Technique of All-digital Modem" is the sub-topic of laboratory "High Data-rate Receiver" project.With the advent of the information age,the amount of data being transmitted in military satellite communications,military satellites,reconnaissance satellites,resource detection satellites have been doubled,prompting the satellite high-speed digital transmission system develop towards higher bit rate,wider bandwidth,higher Spectrum utilization.Because there are many types of spacecraft,the speed,modulation style and coding method of high-speed data transmission are also different.Therefore,the development of satellite high-speed modulator/demodulator must have flexible real-time configuration function.Traditional analog modulation and demodulation system have complex structure,poor reliability,and are vulnerable to environmental impact,cannot be suitable for high-speed satellite data transmission.At the same time,with the develop of ADC sampling rate and digital device technology,common hardware platform that can demodulate multiple modulation signals have emerged,so the current high-speed digital transmission mainly adopts all-digital modulation and demodulation architecture which based on the idea of software radio.In view of the above background,the topic proposed a sample-rate-conversion technique to achieve a broadband rate variable multi-mode all-digital modulation system based on FPGA hardware platform,which act as the analog source and self-test equipment of the receiver.The background of the project and the state-of-art research situation are given in the first part of this paper.Then we describe the theoretical basis of sample-rateconversion technique and MPSK modulation.Next,we illustrate various method to implement sample-rate-conversion and investigate their performance.FPGA implementation of the algorithm,based on the previous theory and interpolation algorithm,elaborated parallel PN sequence generator,32 parallel-channel interpolation filter,data buffer,online configuration module and RTL diagram,Modelsim simulation result are given to verify function and performance of the system.The last part of the paper give the frequency spectrum and EVM for the evaluation of signals at different symbol rate,followed by conclusion.