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Rato, RT, Ortigueira MD, Batista AG.  2008.  The Empirical Mode Decomposition: A Useful Tool for Signal Analysis. New Signal Processing Research. , New York: Nova Science Publishers Abstract
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Rato, RT, Ortigueira M, Batista A.  2008.  The EMD and its use to identify system modes. International Workshop on New Trends in Science and Technology (NTST2008). Abstract
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Rato, RT, Ortigueira MD, Batista AG.  2008.  On the HHT, its problems, and some solutions. Mechanical Systems and Signal Processing. :1374–1394. Abstract
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Rato, R, Ortigueira MD, Batista AG.  2009.  The Empirical Mode Decomposition an Useful Tool for Signal Analysis. New Signal Processing Research. :455–475.: Nova Science Publishers, Inc., Abstract
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Rato, L, Silva RN, Lemos JM, Coito F.  1997.  Multirate MUSMAR cascade control of a distributed solar field. Proc. of the European Control Conference ECC97. Brussels, Belgium. Abstract

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Rato, RT, Ortigueira MD, Batista AG.  2008.  The EMD and its Use to Identify System Modes. Proceedings of the International Workshop on New Trends in Science and Technology. Abstract
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Rato, R, Ortigueira M.  2005.  A Modified EMD Algorithm for Application in Biomedical Signal Processing, July. International Conference on Computational Intelligence in Medicine and Healthcare, CIMED 2005. Abstract
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Rato, RT, Ortigueira M, Batista A.  2008.  On the HHT, its problems, and some solutions, August. Mechanical Systems and Signal Processing. 22:1374–1394., Number 6: Elsevier AbstractWebsite

The empirical mode decomposition (EMD) is reviewed and some questions related to its effective performance are discussed. Its interpretation in terms of AM?FM modulation is done. Solutions for its drawbacks are proposed. Numerical simulations are carried out to empirically evaluate the proposed modified EMD.

Ricardo, CN, Gerald JA, Ortigueira M.  2005.  Analysis of New Quasi-Orthogonal BCH-Derived Sequences for CDMA Applications. XX Conference on Design of Circuits and Integrated Systems (DCIS'05). Abstract
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Ricardo, CN, Inácio JA, Gerald JA, Ortigueira MD.  2003.  New BCH-Derived Sequences for CDMA Systems. 46th IEEE - Midwest Symposium on Circuits and Systems. :1255–1258. Abstract

New BCH-derived PN-EB (pseudo-noise even balanced) sequences suitable to be used in CDMA systems are presented in this paper. It is assumed a new definition for processing gain, which better accounts for the system performance regarding the narrow band noise rejection, and it is shown how to obtain high processing gain values, namely, by using zero mean spreading signals in channels with selective noise. The new sequences have low autocorrelation levels, exist in large numbers and can provide higher processing gain with selective noise.

Ricardo, CNE, Ortigueira MD, Gerald JAB.  2007.  New quasi-orthogonal BCH-derived sequences for CDMA applications. European Transactions on Telecommunications. 18:803–810., Number 7: John Wiley & Sons, Ltd. AbstractWebsite

Based on two methods recently proposed - the Ranging Criterion (RC) and the Generators Ranging Criterion (GRC) - new (quasi-orthogonal) even BCH-derived sequences are generated which are very attractive for synchronous or quasi-synchronous Code Division Multiple-Access (CDMA) systems. Numerical results show that the new family of BCH-derived sequences can contain a higher number of quasi-orthogonal sequences with lower correlation values and higher processing gains (PGs) than the spreading sequences typically used in the third generation of mobile communications system, UMTS or in the recent large area synchronised CDMA (LAS-CDMA) technology. It is shown that the even BCH-derived sequences are easily generated by a linear shift register generator, allowing the construction of systems with receiver structures of low complexity as compared with those of quasi-synchronous systems using low correlation zone sequences, as for instance the LAS-CDMA system.