Decoupling cap SRF

Andrew Holme · 2011-02-23T20:55:34+00:00

I just tested some ceramic caps on an AIM 4170 impedance analyser:0603 10nF 50V X7RSRF=47.6 MHzZ @ 22.5 MHz: Xs=-0.557, Rs=0.0830603 10nF 25V COGSRF=37.7 MHzZ @ 22.5 MHz: Xs=-0.401, Rs=0.0350603 100nF 16V X7RSRF=8.7 MHzZ @ 22.5 MHz: Xs=+0.304, Rs=0.062I'm building a 22.5 MHz IF amplifier and can't decide what decouplers to use. The 100nF has the lowest impedance, so I suppose it would make the best decoupler; but its SRF is less than half the operating frequency! Which would you use?TIA

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Dave Platt 15 years ago

Thanks, I'll see if I can find one! The BAMA mirror has a 1S1 manual, which I have just sent to the printer... with luck it will have some of the similar theory sections.

Well, if you ever do, I can give it an alternate home!

The 7S series apparently came with some transparent templates you could place over the screen to give you a similar reading capability, but they weren't included with the used plugin I bought.

My thought was to capture (digitize) the X- and Y-scan output from the Tek mainframe, and use a laptop to do the calculations. Yet another oddball project I may never have time for, alas.

Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads!

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Phil Hobbs 15 years ago

Tektronix Concepts book on TDR measurements:

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Cheers

Phil Hobbs

Dr Philip C D Hobbs Principal ElectroOptical Innovations 55 Orchard Rd Briarcliff Manor NY 10510 845-480-2058 email: hobbs (atsign) electrooptical (period) net http://electrooptical.net

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Joel Koltner 15 years ago

Note that most decent VNAs from the past couple of decades can perform an FFT for you and display a time-domain trace as well. Most will then let you position a marker at a certain point in time and then re-compute the frequency domain response as if everything prior hadn't occurred, i.e., it's just another method of defining where you reference plane is (although probably not as accurate as building a proper calibration jig in the first place).

Too bad the 11802 can't do an FFT and display a frequency-domain response!

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Dave Platt 15 years ago

Oh, that's beautiful. On first glance it looks as if it's exactly the sort of thing I was hoping to find.

Thank you *very* much indeed!

Dave Platt AE6EO Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads!

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John - KD5YI 15 years ago

Wow! I agree with Dave.

Thanks, Dr. Phil.

Cheers, John

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John - KD5YI 15 years ago

Hey, Dave -

Beware! Page 73 is out of place. It is stuck between pages 75 and 76.

Cheers, John

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Dave Platt 15 years ago

Thanks! I'll stick a sticky-tab on the copy I printed to help me find my way to it :-)

-- Dave Platt AE6EO Friends of Jade Warrior home page:

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I do _not_ wish to receive unsolicited commercial email, and I will boycott any company which has the gall to send me such ads!

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Fred Bartoli 15 years ago

Joel Koltner a écrit :

You still can post process it...

Thanks, Fred.

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Joel Koltner 15 years ago

Good point. I suppose the reason it isn't a built-in option is due to the number of data points being relatively low, plus the fact that for TDR you often care about the various transitions between connectors/components/etc. whereas on a VNA you often specifically want to *ignore* those effects and just look at, e.g., a filter in the middle of it all or whatever.

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Decoupling cap SRF

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