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Ideal Balun ADS - RF Cafe Forums

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Post subject: Ideal Balun ADS Posted: Thu Dec 29, 2005 5:11 pm

Hello guys:

What's the component for IDEAL balun in ADS...there are a few and i'm not sure which one to use. I need to convert both ways....single to diff. and diff. to single. The components I found are:

Balun1 found under Passive-RF Circuit palette

Balun2 found under Passive-RF Circuit palette

Balun3 found under System-Passive palette

Balun4 found under System-Passive palette

Balun1 and Balun2 don't seem ideal because they involve transmission line parameters and frequency parameter. Balun1 and Balun2 seem to be for diff. to single conversion but again they don't seem ideal.

Balun3 seems like single to differential but Balun4 has differential ports on both sides. I can use Balun3 for single to diff. conversion but what about diff. to single conversion? Do you use Balun4 for that but it has diff. ports on both sides....should i just connect my diff. signal on one side and take out the unbalanced signal from the other side leaving one port 'open'??? Is there any other balun component in ADS??



Post subject: Posted: Thu Dec 29, 2005 6:55 pm

Any response?? I thought I might try Balun3. Is it ok if I use Balun3 component in ADS like the image below. also, should this setup give me matched condition to 50 Ohm. I ran the simulation and didn't get exact match to 50 Ohms so I was wondering if something is wrong here with the balun setup. also does any one know how to use zin() function within the schematic in ADS. thanx



Post subject: Posted: Sat Dec 31, 2005 2:15 am

I believe the 2 outputs should be 25ohms.




Post subject: Posted: Tue Jan 03, 2006 7:26 am

No, I think your setup is correct...you specify an impedance for the ideal balun: i.e. Zo=50 and this will set each port to 50 ohms. since one port is grounded on the single ended side, you will terminate the other port to 50 ohms....that's what i think




Post subject: Posted: Wed Jan 04, 2006 3:21 am

Well, I think you're wrong. For the same reason a power splitter requires a 2:1 tranformer at it's intput.

If the BALUN was being used with a balanced output it would require a single 50ohm resistor from output+ to output-. That's because it's a 1:1 balun.

ohhh SNAP!



Post subject: Posted: Thu Jan 05, 2006 2:35 am

What's the matter? Is that all you got?

You're lucky there's a Moderator here!



Post subject: Posted: Sat Jan 07, 2006 11:52 am

Hi Rod,

No need to fight here although. DisAgree and you're on the wrong page.

This setup will not match as it is given (and will match if 25 Ohms each is on the differential side) but I think the guy wanted to know about ideal Balun in general and I think his setup would not correctly tell what the Balun is doing because he's grounding the differential side impedances. Isn't that right? If there was an actual balanced output and each side of the balanced output was matched to 50 Ohms and then an ideal balun was used to convert the balanced to single ended then I think you will terminate it in 50 Ohms and not 100 Ohms.

So, the setup shown by the guy, yes it's wrong and will not match unless impedance on the differential side sums up to 50 but I think the guy was asking what would actually happen if one tries to convert a balanced output that has its each side matched to 50 Ohms to single ended. In that case you do terminate in 50 Ohms. Rod your thoughts welcomed!!



Post subject: Posted: Mon Jan 09, 2006 1:08 pm

I'm sorry, I'm just extremely sensistive. I am also right!



Post subject: Posted: Mon Jan 09, 2006 2:16 pm

Hi guys. I have an opinion, but shan't present it here because level heads do not prevail. Here's a simple empirical solution to determine who is correct:

Connect a 50 ohm source to TERM2 and look at the VSWR with 50 ohms on each of the differential ports, and then with 25 ohms on each differential port. Whichever setup results in a 1:1 VSWR wins.



Post subject: Posted: Mon Jan 09, 2006 2:34 pm

Yeah, you can do that if you want to burn precious calories.

Mike already mentioned in his second post he was not seeing a good match.

You guys need to lighten up and just admit..YOU GOT SERVED!

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