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Author Topic: ASCII transfer export- spreadsheet editing  (Read 2012 times)

Hayden J. Nebus

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ASCII transfer export- spreadsheet editing
« on: May 09, 2015, 05:34:29 pm »

I'd like to overlay a pair (DUT and Target)  of imported ASCII Transfer measurements in rePhase. This isn't supported yet by the program.

It occurred to me this can be simulated for the phase responses by replacing the magnitude data in the DUT measurement with linearly-scaled phase data from the target measurement.

If I load both ASCII measurements into excel it should be fairly straightforward. Presuming a wrapped phase scale of +/-180 and an arbitrary linear magnitude scale of 0dB to -90dB,

For each data point in the measurement the magnitude column would equal -45dB+(target phase value/4) 

Where -45dB correlates to zero phase on the shared bode plot, and one degree of phase=0.25dB. If my reasoning is sound, this would result in a pair of validly displayed overlaid phase responses from two measurements.

Any reasons this wouldn't work as intended? Both measurements are identical FFT length and magnitude scaling in the app is linear.

P.S.I'm also presuming there's 3 significant digits of magnitude throughout, which if there's only 2, could result in some minor rounding issues.
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David Sturzenbecher

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Re: ASCII transfer export- spreadsheet editing
« Reply #1 on: May 09, 2015, 09:03:52 pm »

I'd like to overlay a pair (DUT and Target)  of imported ASCII Transfer measurements in rePhase. This isn't supported yet by the program.

It occurred to me this can be simulated for the phase responses by replacing the magnitude data in the DUT measurement with linearly-scaled phase data from the target measurement.

If I load both ASCII measurements into excel it should be fairly straightforward. Presuming a wrapped phase scale of +/-180 and an arbitrary linear magnitude scale of 0dB to -90dB,

For each data point in the measurement the magnitude column would equal -45dB+(target phase value/4) 

Where -45dB correlates to zero phase on the shared bode plot, and one degree of phase=0.25dB. If my reasoning is sound, this would result in a pair of validly displayed overlaid phase responses from two measurements.

Any reasons this wouldn't work as intended? Both measurements are identical FFT length and magnitude scaling in the app is linear.

P.S.I'm also presuming there's 3 significant digits of magnitude throughout, which if there's only 2, could result in some minor rounding issues.

Logically, your method sounds solid.  The only question I would ask is...what good is matching the DUT to the target, if your don't match phase as well?
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Hayden J. Nebus

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Re: ASCII transfer export- spreadsheet editing
« Reply #2 on: May 09, 2015, 10:52:21 pm »

Logically, your method sounds solid.  The only question I would ask is...what good is matching the DUT to the target, if your don't match phase as well?

That's the point, But I assume you meant magnitude? There's already some fairly minimal IIR EQ in line that works fine. I could reinvent it with linear phase filters, but that would take 2 iterations of filter design& measure, vs. 1

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Hayden J. Nebus

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Re: ASCII transfer export- spreadsheet editing
« Reply #3 on: May 09, 2015, 11:26:45 pm »

This rePhase software is incredible. Democracy has come to FIR filters.

Its freeware and in V0.9.9. ..I saved 2 copies, before someone realizes it should cost 2 grand!
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David Sturzenbecher

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Re: ASCII transfer export- spreadsheet editing
« Reply #4 on: May 10, 2015, 09:15:51 am »

That's the point, But I assume you meant magnitude? There's already some fairly minimal IIR EQ in line that works fine. I could reinvent it with linear phase filters, but that would take 2 iterations of filter design& measure, vs. 1

When I wrote the message, I definitely meant phase...but after re-reading your initial post, you are correct. I have played around quite extensively with re-phase about 6 to 9 months ago. Planning on peeling back a few more onion layers here again soon.
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Tim McCulloch

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Re: ASCII transfer export- spreadsheet editing
« Reply #5 on: May 12, 2015, 08:17:53 pm »

This rePhase software is incredible. Democracy has come to FIR filters.

Its freeware and in V0.9.9. ..I saved 2 copies, before someone realizes it should cost 2 grand!

Thanks for the heads up on rePhase.  I gots some learnin' to do. :)
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David Sturzenbecher

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Re: ASCII transfer export- spreadsheet editing
« Reply #6 on: May 12, 2015, 08:36:16 pm »

Thanks for the heads up on rePhase.  I gots some learnin' to do. :)

Tim,
Silas taught me a trick on how to directly import FIR coefficients into ITHD's.  PM me if your interested.
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