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njit-etd2003-081 - New Jersey Institute of Technology

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Figure 5.5 Test signal with 3 sine waves at 0.3, 0.1 and 0.5 Hz (top) and its power spectrum<br />

(bottom).<br />

The Morlet wavelet, as well as the Meyer, Daubechies 4, Mexican Hat and Haar<br />

wavelet used, clearly shows the more defined pictures <strong>of</strong> the 3 sine waves representation<br />

with little interference (or cross-terms) when compared side-by-side with the STFT,<br />

PWVD, CWD and BJCD <strong>of</strong> the time-frequency representations. The Morlet wavelet may<br />

still not be the best wavelet type used in analyzing the low frequency range (below 2 Hz)<br />

<strong>of</strong> HRV but still is better than the other time-frequency representations presented here.<br />

The results obtained from the test signal indicate that the linear time-frequency<br />

representations (CWD and wavelets) are the preferred time frequency distributions and<br />

the Morlet wavelet analysis is the better method to use for HRV.

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