tune out a wideband balun?

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.

Yes, the lumped LC baluns are narrow band.

How to get wideband balun then? I have heard transformers can give wider bandwidth then L match. How?

http://www.rfmd.com/CS/Documents/RF2...teSPACE2.0.pdf

A wideband balun can be only implemented by a transformer, either transmission line or conventional type.

The original question is however very vague, talking about "1 nH" balun (transformer with 1 nH inductance?) without telling a frequency range. 1 nH inductance will be too low even for GHz frequencies without a resonant circuit.

Hi vfone & FvM,
Thank you very much!
FvM: I basically want 180 phase shift between two points over frequency range 10MHz to 2.5GHz without active devices. I am planning to use a 1: 1 transformer. The 1nH thing is a model I was playing with. I appreciate any suggestions you might have.

"1 nH inductance will be too low even for GHz frequencies without a resonant circuit."
Is it too low because Zin will be very low?

10 MHz to 2.5 GHz is ambitious. Some Mini-Circuits transformers cover the range, e.g. TC1-1-13M as 1:1 balun. http://217.34.103.131/pdfs/TC1-1-13M+.pdf

Hi FvM,
I am taking about onchip transformer in a CMOS process. Is it possible to have one? Its also OK for me if I can simultaneously have narrowband (tuned out) matching in 10MHz and 2400MHz. Is it possible to design a tuned transformer which is tuned at two frequencies i.e. 10MHz and 2400MHz?

It's just impossible to make transformers for the low MHz range without a core, nor the inductor values required for a lumped balun. Simply forget about on-chip impedance matching or balun for the low MHz range. Active circuits are the only option.

Thank you FvM!