Spectrum analyzer blind spots

FFTs,

tes

ant

So you aren't talking about splicing them together then. You're talking about simply taking overlapping blocks from the data stream. That's so simple (in concept at least) that I don't think you'll find much literature devoted specifically to how to do it. You'll find mention of it in various ap notes for at least the box-type dynamic signal analyzers, and in the help text. It comes down to using overlap when you can: if your data stream is 100Ms/s and you are doing 1M point FFTs, you need quite a bit of processing power to keep up. "Keeping up" is commonly called "real-time processing" or something similar. So the bandwidth that supports real-time for some particular length FFT could be an important feature when you go to buy an instrument. Just how much overlap you'd like to have depends on how much you want to be sure that you don't miss anything, and what window function you're using. So again, since all of this is tied up so intimately with the whole concept of an FFT-based analyzer, I'd suggest an ap note about the fundamentals of such analyzers: sections

8 and 9 of Agilent ap note 243
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might be a good place to start.

Cheers, Tom

Reply to
Tom Bruhns
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Hi Tom,

Yeah, this is precisely the part I was hoping someone had written something up about. :-)

Thanks for the link...

---Joel

Reply to
Joel Koltner

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Er, Agilent is basically HP. HP is instrumentation. I ignore that computer and printer company.

The radio I spoke of had varactors and switches capacitors. Something like a capacitor "DAC" if you will, to quickly adjust the tuned circuit. Trust me, you would want one. The item I saw came from a destruct order that...well....and a bargain at $1k cash about 15 years ago.

Reply to
miso

FFTs,

tes

ant

You are speaking of periodograms. It is covered well in Openheim/ Schafer. It is probably too complex for ap notes, but as I said, well documented in text books.

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:-) Well, you're entitled to your opinion, but Agilent isn't even like HP used to be, let alone what HP _is_ now. That's not necessarily a bad thing, it just is. Heck, Agilent today is a lot different than Agilent of seven years ago.

Do you suppose that front end you're mentioning has an antenna- referred third order intercept for out-of-band signals in excess of

+60dBm? Considering some of the front-end problems I've worked on, I seriously doubt I'd have any interest at all in something with varactors in it.

Cheers, Tom

Reply to
Tom Bruhns

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