Difference between revisions of "NVGate CBT principle and settings"

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NVGate CBT principle and settings (view source)

Revision as of 14:21, 29 April 2020

1,318 bytes removed ,  14:21, 29 April 2020
→‎b/ Frequency bandwidth definition
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From the curve shown in Picture 3, it is to be seen that applying Hanning weighting window on a pure tone sine wave will result in energy spread between the 2 side spectral lines (-1 and <nowiki>+</nowiki>1 on Picture 3) of sine frequency. Energy on the next spectral lines (-2 and <nowiki>+</nowiki>2 on Picture 3) will be reduced to 0 amplitude.
From the curve shown in Picture 3, it is to be seen that applying Hanning weighting window on a pure tone sine wave will result in energy spread between the 2 side spectral lines (-1 and <nowiki>+</nowiki>1 on Picture 3) of sine frequency. Energy on the next spectral lines (-2 and <nowiki>+</nowiki>2 on Picture 3) will be reduced to 0 amplitude.


[[Image:CBT_03.gif|framed|none]]
 


Picture 3: Hanning weighting window
Picture 3: Hanning weighting window


In this case, if f is the spectral resolution of FFT, f<sub>0</sub> the frequency of a vibration phenomenon, minimum energy calculation for Constant Band tracking should be done at spectral lines:
[[Image:cbt formula.png|framed|none]]
 
<nowiki>[</nowiki>(f<sub>0</sub>-f) <nowiki>+</nowiki> f<sub>0</sub> <nowiki>+</nowiki> (f<sub>0</sub><nowiki>+</nowiki>f)<nowiki>]</nowiki>
 
that is to say a frequency bandwidth of
 
{|border="0" cellspacing="2" width="100%"
|colspan = "3"|CBT min band
|= (f<sub>0</sub><nowiki>+</nowiki>f)-(f<sub>0</sub>-f)
 
|-
|&nbsp;
|&nbsp;
|&nbsp;
|= 2*f
 
|}
 
NOTE: when f<sub>0</sub> is not matching exactly one spectral line (f<sub>0</sub> is not a multiple of f) leakage phenomenon may happen. In this case energy of vibration will be spread on next closest spectral lines (on the left and right). Energy picked up at spectral lines (f<sub>0</sub><nowiki>+</nowiki>f) or (f<sub>0</sub>-f) corresponds itself to the energy component measured on a frequency band of <nowiki>[</nowiki>f<sub>0</sub><nowiki>+</nowiki>f-; f<sub>0</sub><nowiki>+</nowiki>f<nowiki>+</nowiki><nowiki>]</nowiki> or <nowiki>[</nowiki>f<sub>0</sub>-f-; f<sub>0</sub>-f<nowiki>+</nowiki><nowiki>]</nowiki>, where  correspond to leakage bandwidth. In OROS OR2x,  was considered to be equivalent to f/2.


=====c/ Phase calculation in Constant Band Tracking=====
=====c/ Phase calculation in Constant Band Tracking=====
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