Research On The Key Techniques For SDR Receiver

Software radio is one of the hotspots in radio communication and military communication research. It is a good solution to many existing problems, such as the interconnection of various communication architectures and radio standards, using up of radio spectrum, poor cooperative capability, overspending of military expenditure, and so on. In order to make a research on the software radio, this thesis focuses on key techniques for radio receiver including: DDC technology, the channelization model, modulation and demodulation algorithm. The DDC (Digital Down Conversion) technology performs down conversion, narrowband low pass filtering and decimation to produce a base-band signal, so that the signal can be processed by DSP in real-time. A software DDC algorithm proposed in virtual radios is studied in this dissertation. And in order to reduce the sampling rate and minimize the processing, a group of special cascade filters are studied in detailed in its character and realization method. For multi-channel signal, according to multi-rate signal processing theory, the poly-phase filtering technique can help reduce the workloads of DDC, 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 (the MSK modulation and demodulation algorithm is researched in this dissertation), if can use complex carrier orthogonal modulation, can be used in the system.