8,877
edits
Difference between revisions of "NVGate Formula Computation"
Jump to navigation
Jump to search
NVGate Formula Computation (view source)
Revision as of 15:58, 13 January 2022
, 15:58, 13 January 2022→Cepstrum
| Line 152: | Line 152: | ||
A high "quefrency" represents rapid fluctuations in the spectrum (small frequency spacings) and a low "quefrency" represents slow changes with quefrency (large frequency spacings). Note that the quefrency does not give information on the absolute frequency but only about frequency spacings. | A high "quefrency" represents rapid fluctuations in the spectrum (small frequency spacings) and a low "quefrency" represents slow changes with quefrency (large frequency spacings). Note that the quefrency does not give information on the absolute frequency but only about frequency spacings. | ||
===Envelope spectrum=== | |||
The envelope is compute from the zoomed spectrum signal by taking the module multiplied by 2. | |||
This corresponds to an Hilbert transform (signal multiplied by itself but out of phase by 90 ). | |||
Indeed to compute the zoom spectrum, it is necessary to compute 2 signals: | |||
R (t) = input (t) * cos (2 * PI * fc * t) | |||
I (t) = input (t) * sin (2 * PI * fc * t) | |||
With fc = Zoom center frequency ; input (t) = input signal. | |||
Then The signals R (t) and I (t) are decimated (zoom factor: 2, 4, 8…). | |||
Then We compute the zoom signal complex spectrum of the zoomed signal. | |||
And the envelope signal is equal to : | |||
Env (f) = 2 * sqrt (RZ (f) * RZ (f) + IZ (f) * IZ (f)) | |||
With : RZ (f) = real part of the zoomed spectrum (at frequency f) | |||
IZ (f) = imaginary part of the zoomed spectrum (at frequency f) | |||
===Measurement scalar Level=== | ===Measurement scalar Level=== | ||
[[Image:formula_16.png|framed|none]] | [[Image:formula_16.png|framed|none]] | ||