NVGate Formula Computation - Revision history

Lmagimel at 09:00, 26 November 2024

2024-11-26T09:00:11Z

← Older revision		Revision as of 11:00, 26 November 2024
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			[[category:WikiOros]]
	Description of NVGate Computation: This document describes the different computations that are done inside the analyzer.		Description of NVGate Computation: This document describes the different computations that are done inside the analyzer.

2022-01-14T07:19:58Z

Envelope spectrum

← Older revision		Revision as of 09:19, 14 January 2022
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	===Envelope spectrum===		===Envelope spectrum===

			The envelope signal is computed from the zoomed signal by taking the module of the complex signal multiplied by 2.

	~~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° ).		This corresponds to an Hilbert transform (signal multiplied by itself but out of phase by 90° ).

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	With : RZD (t) = real part of the zoomed signal after decimation		With : RZD (t) = real part of the zoomed signal after decimation

	IZD (t) = imaginary part of the zoomed signa after decimation		IZD (t) = imaginary part of the zoomed signa after decimation

2022-01-14T07:19:12Z

Envelope spectrum

← Older revision		Revision as of 09:19, 14 January 2022
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	Then The signals R (t) and I (t) are decimated (zoom factor: 2, 4, 8…).		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 (t) = 2 * sqrt (RZ (t) * RZ (t) + IZ (t) * IZ (t))~~		The envelope signal is equal to :

	~~With : RZ~~ (t) = ~~real part of the zoomed signal~~		Env (t) = 2 * sqrt (RZD (t) * RZD (t) + IZD (t) * IZD (t))

	IZ (t) = imaginary part of the zoomed ~~signal.~~		With : RZD (t) = real part of the zoomed signal after decimation
			IZD (t) = imaginary part of the zoomed signa after decimation

	===Measurement scalar Level===		===Measurement scalar Level===

	[[Image:formula_16.png\|framed\|none]]		[[Image:formula_16.png\|framed\|none]]

2022-01-13T15:06:56Z

Envelope spectrum

← Older revision		Revision as of 17:06, 13 January 2022
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	The envelope is compute from the zoomed spectrum signal by taking the module multiplied by 2.		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 ).		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:		Indeed to compute the zoom spectrum, it is necessary to compute 2 signals:

2022-01-13T15:03:59Z

Envelope spectrum

← Older revision		Revision as of 17:03, 13 January 2022
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	And the envelope signal is equal to :		And the envelope signal is equal to :

	Env (f) = 2 * sqrt (RZ (f) * RZ (f) + IZ (f) * IZ (f))		Env (t) = 2 * sqrt (RZ (t) * RZ (t) + IZ (t) * IZ (t))

	With : RZ (f) = real part of the zoomed ~~spectrum (at frequency f)~~		With : RZ (t) = real part of the zoomed signal

	IZ (f) = imaginary part of the zoomed ~~spectrum (at frequency f)~~		IZ (t) = imaginary part of the zoomed signal.

	===Measurement scalar Level===		===Measurement scalar Level===

	[[Image:formula_16.png\|framed\|none]]		[[Image:formula_16.png\|framed\|none]]

2022-01-13T14:59:14Z

Envelope spectrum

← Older revision		Revision as of 16:59, 13 January 2022
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	Indeed to compute the zoom spectrum, it is necessary to compute 2 signals:		Indeed to compute the zoom spectrum, it is necessary to compute 2 signals:

	R (t) = input (t) * cos (2 * PI * fc * t)		R (t) = input (t) * cos (2 * PI * fc * t)

	I (t) = input (t) * sin (2 * PI * fc * t)		I (t) = input (t) * sin (2 * PI * fc * t)

	With fc = Zoom center frequency ; input (t) = input signal.		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 The signals R (t) and I (t) are decimated (zoom factor: 2, 4, 8…).

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	With : RZ (f) = real part of the zoomed spectrum (at frequency f)		With : RZ (f) = real part of the zoomed spectrum (at frequency f)

	IZ (f) = imaginary part of the zoomed spectrum (at frequency f)		IZ (f) = imaginary part of the zoomed spectrum (at frequency f)

2022-01-13T14:58:44Z

Envelope spectrum

← Older revision		Revision as of 16:58, 13 January 2022
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	I (t) = input (t) * sin (2 * PI * fc * t)		I (t) = input (t) * sin (2 * PI * fc * t)
	With fc = Zoom center frequency ; input (t) = input signal.		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 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.		Then We compute the zoom signal complex spectrum of the zoomed signal.
	And the envelope signal is equal to :		And the envelope signal is equal to :

	Env (f) = 2 * sqrt (RZ (f) * RZ (f) + IZ (f) * IZ (f))		Env (f) = 2 * sqrt (RZ (f) * RZ (f) + IZ (f) * IZ (f))

	With : RZ (f) = real part of the zoomed spectrum (at frequency f)		With : RZ (f) = real part of the zoomed spectrum (at frequency f)
	IZ (f) = imaginary 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]]

2022-01-13T14:58:29Z

Cepstrum

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 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.
 ===Measurement scalar Level===
 [[Image:formula_16.png|framed|none]]

2020-12-29T14:56:50Z

Computation of overall Level

← Older revision		Revision as of 16:56, 29 December 2020
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	You will find it on [[NVGate_Weighting_Windows_appendix\|weighting windows page]]. To sum up:		You will find it on [[NVGate_Weighting_Windows_appendix\|weighting windows page]]. To sum up:

	ENBW rectangular windows = 1		ENBW rectangular windows = 1<br>
	ENBW hanning windows = 1.5
	ENBW hamming windows = 1.36		ENBW hanning windows = 1.5<br>
	ENBW kaiser bessel windows = 1.8
	ENBW Flat Top windows = 3.77		ENBW hamming windows = 1.36<br>

			ENBW kaiser bessel windows = 1.8<br>

			ENBW Flat Top windows = 3.77<br>

	-----		-----

2020-06-29T07:57:14Z

Computation of overall Level

← Older revision		Revision as of 09:57, 29 June 2020
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	===Computation of overall Level===		===Computation of overall Level===
	'''Frequently asked question :~~''' '''~~Why the overall RMS level of my Spectrum mismatches with the sum of spectrum lines ?'''		''Frequently asked question : Why the overall RMS level of my Spectrum mismatches with the sum of spectrum lines ?''

	ENBW is the key... :)		ENBW is the key... :)