Multiple lumped component to achieve wideband LNA from 400MHZ to 1GHz

Hi all,
I've been doing a project which is design a wideband lna from 400MHz to 1GHz using normal transistor ( Model: BFG 198 )

I've added few L network into the circuit, and i get desire result, which is >12dB from 400MHz to 1GHz. and sufficient input and output loss (< -10dB).
BUT i need the explanation behind this theory.

Thanks~~