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Specs on microwave power divider/combiners

I'm thinking that something like this:

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...is a multi-stage Wilkinson divider internally. I'm curious how they decide to specify its frequency range... anyone know? Based on this data sheet and others I've looked at, I'm thinking that the low-end (1.7GHz) is spec'd based on the isolation between the split/combined ports becoming "unreasonably" low (20dB, or thereabout), whereas the high-end (9GHz) is based on the insertoin loss becoming "unreasonably" high (~1dB over theoretical minimuum).

If you're just using a Wilkinson like this as a splitter and have a very good match on the output ports, presumably you can use it to much lower frequencies? At DC, for a 50-ohm 2-way Wilkinson, the input is looking at 25 ohms (=VSWR of 3:1=return loss of -9.5dB, still acceptable in some cases) and (since at this point it's just a resistive splitter, really) the overall insertion loss is also 9.5dB or 6.5dB over the minimum.

---Joel

Reply to
Joel Koltner
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Your logic seems reasonable to me.

I'll add that it's possible that with a specified maximum input power of 10 watts, it won't take much insertion loss to hit the specified

125 mw internal dissipation limit. Methinks something is fishy here as that's -0.06 dB maximum internal loss. Maybe they mean 125 mw over the specified 0.5dB insertion loss. However, 0.5dB loss with a 10 watt input, is 1.09 watts dissipated, which is quite a bit more than the specified 125 mw internal dissipation. Nice muddle here.

Some more clues can be found in the Power Splitter FAQ at: (Sept 8, 1999) Q. Can performance parameters be traded off when specifying power splitter/combiners?

A. Once frequency range has been designated, there is not too much leeway in tradeoffs between the various spec parameters. Usually all the performance parameters of a well designed power splitter simultaneously fall off as a function of frequency. However, near the band edge, isolation may be improved at the expense of VSWR by adjusting the value of the internal load resistor Zo.

There are other performance tradeoffs hinted further down the FAQ.

Not very specific, but enough to tell that MCL apparently specifies the frequency range first, and then tweaked the performance parameters to fit. Whether you consider 3:1 input VSWR and/or 5dB loss to be acceptable performance, is your problem.

I was hoping to find a test circuit and procedure, that might give a better answer, but I couldn't find anything.

--
Jeff Liebermann     jeffl@cruzio.com
150 Felker St #D    http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann     AE6KS    831-336-2558
Reply to
Jeff Liebermann

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FWIW, this is the inside of a MECA 802-4.2.5 power divider.

Reply to
miso

Thanks Jeff, that's a lot of good insight!

Reply to
Joel Koltner

Two stages -- nice!

Microwaves101 has a bunch of good information (and references) on actually desgining these things (and lots of other stuff -- it's an incredibly good web site):

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---Joel

Reply to
Joel Koltner

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