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USB signal generator

I (still) need to test an amplifier for THD in the 1 to 10 MHz range, so I need a very good sine wave to go in.

I was figuring that I could start with a mediocre sine wave and run that through a passive LC bandpass filter at each test frequency, to clean out the residual harmonics. I could put a DDS chip on a board, which would need a uP to program it. Or I could buy some little USB sig gen box to give me the basic sine wave.

A DDS chip might give me -70 dB harmonics, which I could easily filter down to -100. Boxed signal generators probably aren't that good.

Any recommendations for a good little USB signal gen? Joerg?

It would be handy if it was easy to program from Python in Linux, and not need some dedicated app.

A little USB signal generator might be fun to have around anyhow.

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John Larkin         Highland Technology, Inc 
picosecond timing   precision measurement  

jlarkin att highlandtechnology dott com 
http://www.highlandtechnology.com
Reply to
John Larkin
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Why not a bench Sig gen? My Rigol is OK... I've used it on some ~100kHz to 1 MHz signals, where the second harmonic could just be seen*.... I'm not sure how much, and did not look for third.

George H.

  • this was a weak 'two-photon' signal and any second harmonic would show up as big 'one photon' signal.
Reply to
George Herold

standard approach to get better than -70 dBc is

lpf in the generator hpf in the analyzer

you'll need both

m
Reply to
makolber

Or bandpass+notch filters.

I need a maybe 1 volt RMS into the 50 ohm DUT impedance, and then it has a 3 volt differential output. At some point, things like inductors and transformers start having their own distortion, which the vendors seldom mention.

--

John Larkin         Highland Technology, Inc 

lunatic fringe electronics
Reply to
John Larkin

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