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Nano satellite technologies have been recognized as potential candidates for new satellite applications. We have developed a X-band downlink system for nano satellite employing Consultative Committee for Space Data Systems (CCSDS) 131.2-B-1 signaling formats with a modulation symbol rate of 100 Msps. Since nano satellites with a mass of less than 50 kg have more constraints than typical large satellites, the received signals of nano satellites tend to suffer much more distortion due to the system and channel constraints. To compensate for the distortion, several techniques have been developed to provide higher data rate than 100 Mbps for nano satellites. At the transmitter, a look-up table (LUT) based digital predistorter for memoryless AM/AM and AM/PM nonlinearities is designed to mitigate nonlinearity of power amplifier (PA) and IQ-imbalance of quadrature modulator. At receiver side, a soft interference canceller (SIC) turbo equalization combined with SCCC turbo decoder has developed to overcome nonlinear/linear distortion using iterative techniques. For 16-QAM modulation, a nonlinear compensation technique based on centroid estimation at the receiver is also developed to correct constellation points of received signals. The techniques are modeled and verified via computer simulation; therefore, the obtained results apply to the downlink system designs of the nano satellite, "Hodoyoshi 4".

SCCC Turbo Equalizer/Decoder for X-band Nano Satellite High-Speed Downlink System