Instrumentation & Measurement Magazine 26-2 - 35

the distribution rules of freFig.
4. The waveforms of s1(t), s2
(t) and s3
(t) in the time-domain.
The information points in Fig. 5a are numerous and scattered
in the whole spectrogram, so it is difficult to directly
extract the time-frequency characteristics of the signal. While
the information points in Fig. 5b are concentrated in the interval
of 3.0~14.0 ms and 10~17 kHz, the information point
distribution law is more intuitive. Observing the pink boxed
areas, the information points in Fig. 5b and Fig. 5c are more
prominent and are concentrated between 2.5~8.5 ms and
10~17 kHz. Fig. 5d shows that the key information points of
the smoothed HHT spectrum in 2.5~8.5 ms are more than the
original HHT spectrum. It proves that smoothed HHT makes
quency components more
obvious. Moreover, according
to the data in the
pink boxed areas of Fig. 5d,
there are more key information
points and a more
balanced distribution in
Fig. 5b in 2.5~7.5 ms, while
there are few key information
points in Fig. 5c
and more filtered information
points after 3.5 ms. It
means that the smoothed
spectrum obtained by using
different smoothing
vectors will have different
performances. Therefore,
the selection of the smoothing
vector should be considered in the practical application of
the algorithm.
Representation of Optimization Time-frequency
Spectrum After Self-feedback
By the performance of different smoothing vectors, illustrated
in Fig. 5, K1
is selected as the smoothing vector to process signals.
The optimized HHT time-frequency spectrums after
primary and secondary self-feedback are obtained, as shown
in Fig. 6. Areas with relative intensity> 0.3 are outlined by pink
boxes. To better observe the distribution and intensity changes
Fig. 5. (a) HHT time-frequency spectrum of s1
frequency spectrum of s1(t) with K2
April 2023
(t); (b) Smoothed HHT time-frequency spectrum of s1
(t) with K1
as the smoothing vector; (c) Smoothed HHT timeas
the smoothing vector; (d) Statistical diagram of effective information points with relative intensity > 0.5.
IEEE Instrumentation & Measurement Magazine
35

Instrumentation & Measurement Magazine 26-2

Table of Contents for the Digital Edition of Instrumentation & Measurement Magazine 26-2

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