On-Chip balun alternative

Hi -
I work on a UWB application, where I have only 1 input port availabe, but all internal blocks work fully differential.
As I do have only ASITIC available for inductor/balun/transformer modelling, and no propper handbook exists, how to come to a appropriate model now my question:

What alternative exists to come from single to differential structure without using a balun?

Thx in advance,
Tom

It maybe varied by the internal circuits of the diff ports. Say HMC610, attached is diff config and singlle config, one with balun and the other without. The attached comes from the datasheet of the HMC610.

sorry - forgot to mention - I am talking about on-chip balun. I have just 1 input pad available und all other internal on-chip blocks are differential, expecting a differential signal.
so far, the circuit can life without LNA.. thus a single to differential ended LNA is due to the high current of the LNA a no-go.

Tom