CC112x LNA Balun Extra component

[veryevil]

Hi, I'm looking into matching a CC1125 to a Skyworks  SKY65366-21 (or 11) at 459MHz and I'm trying to understand the LNA Balun from all of the TI Reference designs.

In the attached picture I don't understand the purpose of L191.

I understand the 4 component balun but not why there is an inductor between the positive and negative inputs on the balanced side?

The pic is from the 420-470MHz ref design.

Thanks

[veryevil]

Apparently its to provide the LNA transistors with a DC Ground path.

No idea how its calculated an d it surely must effect the balun values.

[BigBoss]

A kind of matching has been used in order to compansate the reactive part of the internal LNA.
Noise matching is another possibility..