A Design And Implementation Of Ultrashort Wave Digital IF Receiver

Software radio is currently one of the hottest research topic in the field of military and mobile communications, the fundamental ideal of this subject is to realize various functions of sampled RF according to loading different software on high speed DSP processing platform. Due to the limitation of the devices development, the way of digitalizing the analog signal at IF is usually adopted in the present software radio system, and all the process of digital signals are completed at baseband. The receiver which uses this structure is called digitalized IF receiver.The implement method of ultrashort wave Software radio digital IF receiving module is discussed in this thesis. The basic signal process theory of IF digitalization via ultrashort wave is given, including sampling theory, the digital orthogonal mixing transform, multispeed signal process, digital filter and FM demodulation. Then the receiver structure and mathematical model,signal collection chip and FPGA–main implementation device of digital down conversion are introduced. The application of FPGA to realize digital down conversion, instead of specified device, could change the receiver into a better software radio structure, with higher flexibility and expansibility.After introducing the structure of the digital down conversion, how to achieve digital down conversion using software in FPGA, including selection of sampling rate, generate of sampling clock, achieve of NCO, filter and FM demodulation are described.