Reference sideband setting in SpectreRF

Hi all, I simulated a noise figure of mixer by spectreRF, but I met a problem
in the setting of pnoise. By the user's manual of Cadence, it told me if the
mixer is down converter, I have to set reference side band for -1, and set it for +1 if the mixer is up converter. But, I got a converse result in simulation, I think
it's correct to set the reference sideband as +1 if the mixer is donw converter.

Anything I wrong? Did you guys meet the same problem as mine?
Thanks,