can my passive mixer add a buffer?

I am designing a passive mixer for a heterodyne receiver. It is a broadband mixer.
And after mixing, it is IF=200MHz.

And I want to connect a filter behind the mixer. The filter needs 50 Ohm source and 50 Ohm load.

In order to provide 50 Ohm resistor for filter, I add a source follower. The follower has gm=20mS.

Question:
When I connect 50 Ohm resistor directly at the mixer out, the mixer has 11dB noise figure.
However，when I add a buffer and a 50 Ohm resisitor like the upload file ，its NF becomes 15dB.

15dB noise is too large，because conversion gain is negative.

How can I reduce NF？

I think your gate connection of PMOS current load for PMOS source follower is wrong.