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Design >> RF Design >> tune out a wideband balun?
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Message started by mixed_signal on Mar 1^st, 2014, 10:23pm

Title: tune out a wideband balun?
Post by mixed_signal on Mar 1^st, 2014, 10:23pm

Hi,
I am trying to implement a wideband balun as an intermediate stage in a CMOS receiver.

I want to have Real(Zin)=Rload where Zin is input impedance looking to primary when secondary has a load Rload in 1:1 balun with l1=l2=1nH and k=1 . (ideal)

Is it necessary to tune out the inductors of the balun? I yes then it becomes a narrowband system.

If I dont tune then Zin, Real (Zin) becomes inductive and has very low real part.

Title: Re: tune out a wideband balun?
Post by aaron_do on Mar 9^th, 2014, 8:44pm

Hi mixed_signal,

you do need to resonate the balun in order to minimize loss. However, as I remember it, the balun will give you a wider bandwidth than if you had used an LC. Also, for high impedance ratios, baluns are also less lossy. I wish I had my previous references with me so I could give more information, but it would be quite a chore finding them since I changed jobs.

There are papers on power amplifier design which do a lot of analysis on baluns if you are interested. If I remember correctly, look for an author named Ichiro Aoki formerly from Axiom...

regards,
Aaron