Noise figure of differential signal

Hello, in my circuit i have input RF Vsin  signal and a differential signal from both sides of the capacitors as shown bellow. 

The noise simulation shown bellow demands a PORT input for the NF calculation, if i enter source input instead its just not running the simulation

but when i enter a PORT instead of the VSIN source then i get 200dB because there is no input signal (S/N)_in=0 coming from the port

NF=(S/N)_in/(S/N)_out=0/(S/N)_out=0 =>infinty dB

what could be done to simulate properly noise figure , taking Vsin as input ?

Thanks