SinX/X on MDO3014 AFG

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ambios
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Joined: June 30th, 2014, 9:37 am

SinX/X on MDO3014 AFG

Post by ambios » June 30th, 2014, 9:44 am

Hello,

Can someone tell me how & why one would use the SinX/X input from the AFG on the MDO3014? In particular, I'm trying to measure the frequency response of an amplifier that I designed, and I'm thinking the SinX/X function may be useful for this purpose. Alternatively, I can use the broadband noise input along with the spectrum analyzer. Thoughts on the SinX/X?

Thanks

David N
Tektronix Applications
Tektronix Applications
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Joined: July 31st, 2008, 8:26 am

Re: SinX/X on MDO3014 AFG

Post by David N » July 3rd, 2014, 12:07 pm

Sin x/x interpolation is a mathematical process in which points are calculated to fill in the time between the real samples. This function smooths out the transistions between the sample points the AFG is using to create its ouput waveform. You can read more about Sin X/X in the Tektronix XYZ's of Oscillscopes.

You can download a copy at: http://info.tek.com/XYZs-of-Oscilloscopes-LP.html

ambios
Posts: 2
Joined: June 30th, 2014, 9:37 am

Re: SinX/X on MDO3014 AFG

Post by ambios » July 4th, 2014, 1:17 pm

Thanks for the help.

Much appreciated.

Carl M
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Tektronix Applications
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Joined: July 30th, 2008, 4:45 pm

Re: SinX/X on MDO3014 AFG

Post by Carl M » July 7th, 2014, 5:15 pm

with respect to digital oscilloscopes, sinx/x is interpolation used it improve the display of the waveform and increase the automated measurements accuracy. Hiker already responded with additional information regarding sinx/x interpolation.

With respect to function generation, SinX/X (aka sinc) is a function for output. Sinc is the Fourier transform of a rectangular function. this is really easy to demonstrate and experiment with; have sinx/x function output (the 100 kHz default is fine) from AFG into CH1 of scope. Adjust the scope settings so only one pulse and all of its ringing is on screen (1000 sample record, high res sample mode, 1 us/div). Turn on FFT for CH1 and you should see a rectangle of low frequencies. You can adjust the AFG SinX/X repetition frequency and watch the low frequency cut-off change position. The Pulse-Sinc transform relationship (a pulse in one domain is a Sinc in the other) is a fundamental principle of DSP and spectral analysis.

in theory, hitting your amplifier with a sinc pulse would cause your amplifier to shape the resulting FFT with the frequency response. The trick is getting a fast enough sinc to exercise the frequency band of interest and the right oscilloscope time acquisition to make a good FFT.
Tektronix Application Engineer

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