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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Digital frequency demodulation for a laser vibrometer

Cronin, Christopher Joseph 10 November 2009 (has links)
This thesis presents the design and simulation of a digital frequency demodulator applied to a Michelson interferometer-based scanning laser vibrometer. The laser vibrometer is a velocity transducer that produces frequency-modulated signals that have traditionally been optically or electronically frequency shifted from baseband to an intermediate frequency. This shifting produces a narrow band modulation that may be demodulated with standard analog frequency demodulators. This thesis proposes replacing these traditional optics or electronic circuits with a digital frequency demodulator. The optics of a laser vibrometer can be constructed such that a near-perfect baseband quadrature representation is available for the frequency modulation. It will be seen that this representation is well suited for use by a digital frequency demodulator. This thesis applies the arctangent-type digital frequency demodulator to a laser vibrometer and demonstrates its superiority over other digital demodulation techniques. In addition some specialized signal processing to handle the special case of sine-dwell vibration tests is presented. / Master of Science

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