The Research Of Important Characters Of High Frequency Digital Communication Platform Based On The Software Defined Radio Theory

Software Defined Radio (SDR), first proposed in 90's in last century, is a kind of technology which has great future in communication application. It can satisfy the demand of the 3G mobile communication such as the software realization of the system functions and the modularization of the hardware, and make it easy to update the system with less cost.Digital Down/Up Converter(DDC/DUC), modulation and demodulation are discussed in the dissertation as some essencial parts of SDR platform. To utilize the advantages of DSP chips, the system should be computing sources economical. According to digital signal processing theory, the poly-phase FIR can help reduce the workloads of the DDC/DUC. Therefore, adding the complex carrier mixers, the channelization system (a method of using a single wideband facility to transmit many relatively narrow-bandwidth signals.by subdividing the frequency spectrum used in the wideband channel) can be formed utilizing the characters of FFT. As the parts of SDR, such system should also be extensible. Any modulation types, if can use complex carrier orthogonal modulation, such as AM, ASK, MSK, QAM, etc, can be used in the system.