High-Power RF Multiplexer

I would like to be able to switch one 25 Watt 50-Ohm RF source between two 50-Ohm loads, at up to about a 10 kHz switching rate, continuously. The RF will be at up to 2 GHz. I would like the switching between the loads to take about 3 to 5 us, but not more than about 10 us, and give at least 20 or 30 dB of attenuation toward the unselected load when fully switched. And the insertion loss between the source and the selected load should be as low as possible, and no more than 3 dB, but preferrably less than 1 dB.

Is it possible?

If it's possible, does anyone know of a commercially-available unit that already does that? Or, how difficult would it be to design and build one? I assume it's not going to be as simple as just a couple of MOSFET switching circuits. What types of devices might be used?

Also appreciated would be pointers to any datasheets or appnotes that might be relevant.

Thanks,

Tom

Reply to
Tom Gootee
Loading thread data ...

Without fries? Comin' right up, sir:

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Which diode to use depends on the lower end of spectrum you have to switch.

--
Regards, Joerg

http://www.analogconsultants.com/
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Reply to
Joerg

Lots of people, like mini-circuits, make packaged pin diode RF switches.

John

Reply to
John Larkin

On a sunny day (Sat, 05 Dec 2009 10:54:06 -0800) it happened Joerg wrote in :

Those guys do not allow you to use wget to get the pdf: wget

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--20:04:21--

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=> `UM9400_Series.pdf' Resolving
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208.19.99.70 Connecting to
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|208.19.99.70|:80... connected. HTTP request sent, awaiting response... 999 No Hacking

20:04:22 ERROR 999: No Hacking.

Had to use Opera webbrowser and that stupid adobe plugin to read it...

Hope their diodes were made by people with better brains then those who build teh website.

Reply to
Jan Panteltje

teh website.

That's the case with many vendors and the reason I still use the buggy Acrobat Reader.

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Regards, Joerg

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Reply to
Joerg

Sorry, Joerg. I didn't want to irritate people by under-specifying it.

h.

Thanks! I also found this:

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Reply to
Tom Gootee
[...]

That's a great place to start if you have never used PIN diodes before. Agilent also has good app notes (from the HP days).

Once you get the hang of it PIN diodes are really cool and cost-efficient RF switches. Just keep rectification effects in mind, especially at higher power levels. I'd try to find some with long carrier lifetimes in the microsecond range, but that depends on what your lowest frequency will be.

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Regards, Joerg

http://www.analogconsultants.com/
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Reply to
Joerg

Hi Jan, Use Opera to grab the file but change the file handler to "Save to Disk" now you can use what you like to read it.

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Best Regards:
                     Baron.
Reply to
Baron

uild teh website.

tried to set the user-agent in wget to something like ie or firefox?

-Lasse

Reply to
langwadt

On a sunny day (Sat, 05 Dec 2009 21:24:02 +0000) it happened Baron wrote in :

Yes that is a logical way to do it, but it does require people to start a browser. I saved the file from the pdf.

Reply to
Jan Panteltje

On a sunny day (Sat, 5 Dec 2009 13:33:15 -0800 (PST)) it happened " snipped-for-privacy@fonz.dk" wrote in :

Hey, great idea! wget --user-agent=opera

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works! Had forgetten that option. Thank you.

Reply to
Jan Panteltje

browser.

No, it doesn't. I routinely save PDF files from my Netscape 4.78 news reader program that I'm using to read this group . Right click and save link as. I've used it for over 10 years with no problems.

--
The movie \'Deliverance\' isn\'t a documentary!
Reply to
Michael A. Terrell

No ! The browser is started when click the link. You do have to close it afterwards, assuming you don't want to use it for something else.

Just direct Opera to put the pdf in a directory reserved for that purpose. If its useful then I keep it, if not...

Open SuSE 10.3 KDE 3.5.10

--
Best Regards:
                     Baron.
Reply to
Baron

Yes Michael, you're right ! I'm so used to just clicking the link I'd forgotten that works too. ;-)

--
Best Regards:
                     Baron.
Reply to
Baron

On a sunny day (Sun, 06 Dec 2009 17:29:08 +0000) it happened Baron wrote in :

Dunno, different newsreader I suppose.. I just cut and paste the link, although NewsFlex is able to get it by itself. Indeed, kust tried, I can just add it to the URL list, mark it, and select "get marked URls", and it actually works. Would you believe that? Programmed that 10 years ago, forgot all about it. My newsreader:

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Much better then anything else really. It can even download websites, but in the last 10 years so many new http things have appeared, that I think that no longer works reliably.

Reply to
Jan Panteltje

Opps, Should have said my news reader is Knode !

--
Best Regards:
                     Baron.
Reply to
Baron

I didn't see any at min-circuits' website that meet the specs.

Reply to
Tom Gootee

I don't think Mini-Circuits has switches for the power levels you mentioned. Got to roll your own. Solutions "in a can" would be quite expensive.

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Regards, Joerg

http://www.analogconsultants.com/
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Reply to
Joerg

h.

It looks like this should work:

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---------------------------------

Now, another QUESTION:

That switch requires +15Vdc at 80mA and +5Vdc at 40 mA; about 1.4 Watts total.

It would be very nice if I didn't have to run any power leads to the switch.

If I'm willing to sacrifice 2 to 3 Watts of the RF, does anyone see any problem with making a small RF-to-DC power supply?

If the RF is a 1-2 GHz sinusoid of 25 Watts in 50 Ohms, that should be about 35.36 V RMS, or 50.0 V Peak (100V P-P). What would be a good way to get that down to 15 VDC/80 mA and 5 VDC/40mA? The only two even-possibly-reasonable ways that I can think of, off the top of my head, are: 1) rectify, smooth, and regulate it to DC and then feed that to a switch-mode supply to produce the 15V and 5V, or, 2) use a step-down RF transformer to lower the peak voltage and then rectify, smooth, and regulate. Option 2 could involve two secondary windings, for both the 15V and 5V, or I could just do 15V and then also regulate it down to 5V, since it's only at 40mA.

I've never done a DC power supply design using an RF input frequency, and have just now started thinking about this. Would there be any/ many "gotchas"? What would be the best path to try to take, here?

IF the required RF step-down transformer would be small, and available off-the-shelf somewhere, then that way sounds simpler.

Now I'm suddenly wondering if there are even any suitable smoothing caps, for those frequencies and voltages. Maybe a motor-run polypropylene? Does anyone have any ideas? Or is there some entirely- different approach that I should look at?

Maybe I should have done some homework, before asking. But I thought that a quick reality check, first, might be very helpful. All ideas and opinions will be greatly appreciated!

Thanks,

Tom

Reply to
Tom Gootee

n
n
n
d
e

tch.

y-

Or, maybe, at GHz frequencies, the smoothing will be much, much easier than at 60 Hz? Maybe it could be done with simple LC (or RC) low-pass filters?

Reply to
Tom Gootee

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