Study On Digital Filter In Software Defined Radio Based On Down-conversion Technology

Software radio is one of the hot spots in the research domain of the current military and mobile communication. as a result of the processing speed limit of A/D/A and the DSP chip, the present software radio system mostly uses the compromised plan. That is to increase the frequency changer or the running numeral frequent converted algorithm which is under special-purpose numeral, and to change the sampling frequency of intermediate frequency or radio-frequency signal, so that we can guarantee to carry on the real-time signal processing by the general DSP chip. The main goal of the frequent conversion under the numeral is to move intermediate frequent signal which is outputted by the A/D transformation by mixing numeral frequency, and through extraction, completes the task of the channel extraction by filter.The research goal of this article is studying the software radio basic theory thoroughly, comprehending the essential idea of software radio, with the basic of understanding the software radio center in the essential technology foundation, grasping the present developmental situation and the applicable prospect of software radio.The article introduced center signal multi speed rate signal processing theory in the software radio, center highly effective digital filter theory in the software radio and the signal orthogonal transformation theory firstly. It completed the single stage integral multiple extraction, the multi stage integral multiple extraction and the simulative analysis of multi stage two times extraction; It has established the mathematical model of software radio receiver and has completed the corresponding simulative analysis using MATLAB; It completed the design of related digital filter which is suitable for the software radio using the VHDL language.