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World class computing and information science research at Strathclyde...

The Strathprints institutional repository is a digital archive of University of Strathclyde's Open Access research outputs. Strathprints provides access to thousands of Open Access research papers by University of Strathclyde researchers, including by researchers from the Department of Computer & Information Sciences involved in mathematically structured programming, similarity and metric search, computer security, software systems, combinatronics and digital health.

The Department also includes the iSchool Research Group, which performs leading research into socio-technical phenomena and topics such as information retrieval and information seeking behaviour.

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Nyquist - overcoming the limitations

McLean, R.F. and Alsop, S. and Fleming, J.S. (2005) Nyquist - overcoming the limitations. Journal of Sound and Vibration, 280 (1-2). pp. 1-20. ISSN 0022-460X

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Abstract

In digital signal analysis it is not possible by normal methods to retrieve components of frequency in excess of half the sampling frequency, generally referred to as the Nyquist frequency. Any frequency components that exist in excess of this value will give errors in their frequency determination because they will appear as false or 'aliased' signals. A new technique has been developed to unambiguously retrieve signals many thousands times greater than this hitherto stated limitation. A feature of the system is its ability to sample at low frequency and, without further sampling, be capable of unambiguously determining frequency components far in excess of the initial low-frequency sampling rates. Although the approach has its origins in the area of machinery condition monitoring it has applications in numerous other fields, such as lowering the bandwidth of frequency spectra within communication systems. The technique can also be used in reverse to synthesis high-frequency signals from transmitted lower frequencies.