An IF Digital Down-Converter for Software Radio DVB-S2 Receivers

The second generation of DVB specs, DVB-S2, was developed for satisfying the today´s needs for reliable and effective broadband satellite communication services even under `hostile´ conditions. This is achieved by exploiting the new advances in the fields of coding and modulation. Software defined radio (SDR) proves to be an enabling technology for future multimode and reconfigurable satellite receivers. This work presents the design and implementation of a new digital down-converter overter (DDC) architecture that can be integrated into the next generation software radio DVB-S2 receivers. The presented DDC module is based on two cascaded stages of frequency conversion, operating on samples fed by an A/D converter of moderate sampling frequency. The DDC contains also a sample rate conversion subunit which performs decimation on the resulting in-phase and quadrature (I/Q) samples for proper interfacing with demodulator logic at lower rates. The presented DDC has been implemented and tested using field programmable gate arrays (FPGA), while its performance has been evaluated under additive white Gaussian noise and for various DVB-S2 modulation schemes.