Merged Carrier and Timing Recovery Loops QPSK Demodulator based on Iterative Learning Control

This paper presents a new architecture of QPSK demodulator with merged Carrier and Timing Recovery. It is based on Iterative Learning Control (ILC) and statistic approach for the selection of the optimum sampling time. The approach allows to obtain an improvement in terms of robustness and performance, if compared to a classic demodulator composed of a Costas Loop and an Early-Late. The timing recovery block which is merged with the Costas Loop, and is programmed to minimize the Intersymbol interference (ISI) sampling only one sample per symbol. Due to interaction between the carrier and timing recovery, experimental results show that the proposed system is characterized by a fast lock time and high robustness to the noise, if compared with traditional systems composed of separated symbol and frequency recovery. We also evaluated our architecture in terms of Modulation Error Rate (MER) obtaining a better result than the Early-Late.

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