Design of a Fully Digital BPSK Demodulator Integrated into a TT&C Satellite Transponder

One challenge in satellite development concerns to the performance of the communication link and the adopted technology. In this paper, we present the design of a fully-digital BPSK demodulator that is part of a satellite on-board telemetry, tracking and command transponder. The calculations for the determination of several project parameters, the block diagrams and equations of all the functional modules compounding the demodulator are described. The architecture of the demodulator and of some functional modules differs from similar solutions found in the literature. The performance of the proposed demodulator was evaluated by mathematical analysis and computational simulation. Some of such analyzes are original as well as some statistical characterizations of the signals that were done via simulation. In addition, we evaluated the system bit error rate, under various operating conditions, and the variance of the parameters estimated by the carrier and the symbol synchronizers. The results demonstrated that the proposed solution complies with the requirements of the project. In the worst case of operation, the system performance is only 0.3 dB below the theoretical limit, for the condition when the bit error rate is equal to 10^-5.