The Design Of Intermediate Frequency Digital Receiver In Vector Measuring Direction System

This thesis introduces the design process of intermediate frequency (IF) digital receiver used in space spectrum radio supervising and measuring system. The IF digital receiver based on software radio technology adopts the structure of FPGA plus DSP, which is more powerful than other systems in signal processing, and is able to complete IQ demodulation accurately and acquire characteristic of the signal. The following four aspects is included:.Firstly, the theory basis of IF digital receiver is introduced, which includes over-sampling digital mixing receiving scheme and mathematic model with which the scheme is proved correctly.Secondly, the Numerically Controlled Oscillator (NCO) is designed and realized. First, the theory, the merit and noise analyzing is expatiated on, and then the hardware realizing process of IF digital receiver is introduced concretely.Thirdly, the FIR decimating filter under over-sampling is designed and realized. the working theory, the design principle and design process is expatiated on, and the hardware realizing process of the FIR decimating filter is concretely introduced.Fourthly, the system is controlled by DSP. The all-control process of DSP to the system is shown in four aspects including the preprocessing of DSP signal, the read-write realizing to memory units, the filtering result data transport from FPGA to DSP and the software design of IF digital receiver.Finally, several considerations are given to solve the problems and later development.