LNA

[Malluvalasa veeramani]

Hi,

We have designed limiter+lna combination in 8-12GHZ frequency range.

Input return loss is poor, it is only 6dB.

Please suggest me how can I improve input return loss?

Can I try with capacitors tuning? If so, please suggest me how to do tuning.

 

[AMS012]

While more detail always helps to get the best of the members here, I would suggest you to go through IEEE papers. You should be able to get enough information on LNA matching as it is a well known and most common problem one would encounter.

 

[BigBoss]

Hi,

We have designed limiter+lna combination in 8-12GHZ frequency range.

Input return loss is poor, it is only 6dB.

Please suggest me how can I improve input return loss?

Can I try with capacitors tuning? If so, please suggest me how to do tuning.

-6dB is not too bad for that band but should be improved if it's possible.
-In order to improve the Return Loss, you have to know Input Impedance along that band. So s-parameters must be very well known. But there is a constraint at this point: The Bandwidth
Either you can use cascaded Impedance Matching Circuit that have different Matching Sub-Bands or
You can also apply a feedback to improve the Input return Loss by sacrificing a bit of Power Gain.
There are also some particular techniques but two major are these applicable techniques.
-Using variable capacitor is useless at that band. Forget about it.
-Last but the most important one : Use a physically measured components' models in your simulations.
You should knock the door of Modelithics.( Modelling Company )
-Limiter will also tickle the LNA, take this caution into account. Consider the system has many parameters to play around.

 

[vfone]

You are using a limiter+LNA combination. That means the limiter is first in place, and actually you are measuring the return loss of the limiter, which is a different story.
Show your schematic and we may give you some ideas.