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njit-etd2003-081 - New Jersey Institute of Technology

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CHAPTER 3<br />

ENGINEERING BACKGROUND<br />

The transformation <strong>of</strong> the electrocardiogram, blood pressure and respiration signals into<br />

heart rate variability, blood pressure variability and respiration spectra requires many<br />

intermediate steps such as peak detection, interpolation, resampling and spectral<br />

analysis. To date, there are no standardized ways to process this data to study heart rate<br />

variability, blood pressure variability, and respiration. This leads to varying<br />

experimental results and difficulties in the comparison <strong>of</strong> the experimental results from<br />

one research facility to another.<br />

The purpose <strong>of</strong> this chapter is to introduce a brief background <strong>of</strong> various signalprocessing<br />

methods used in this dissertation. First, a brief introduction to timefrequency<br />

distributions is presented. The uncertainty principle, the concepts <strong>of</strong> analytic<br />

signal, instantaneous frequency and the desired properties <strong>of</strong> the time-frequency<br />

distribution are discussed. The importance <strong>of</strong> covariance and invariance notion <strong>of</strong> the<br />

density function as an operator in the time-frequency distribution is mentioned. A brief<br />

theoretical background comparison <strong>of</strong> the short time Fourier transform, Wigner,<br />

windowed Wigner, Choi-Williams distributions and wavelets are discussed. Other<br />

methods <strong>of</strong> analysis including spectral analyses <strong>of</strong> HRV and BPV are also presented.<br />

The concepts <strong>of</strong> the cross-spectral analysis (coherence, weighted coherence, and partial<br />

coherence) and system identification are covered. Finally, the classification technique<br />

using principal component analysis and cluster analysis are also presented in detail.<br />

42

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