Impact of switch width on mixer output.

Hello,

I am currently occupied with a passive single-balanced mixer as
shown in Fig.1 . ../imgqa/eboard/Antenna/rf-oiegn2btjkc.jpg
After running PAC simulation at Cadence,according
to this paper :

"Analysis and Optimization of Current-Driven Passive Mixers in Narrowband Direct-Conversion Receivers",

the output or baseband voltage should not be affected by the size of the switches.

However,by changing the width of the switch transistors,for example from
5um to 50um I get these results :

../imgqa/eboard/Antenna/rf-vgvvhc5lolb.jpeg

Can anyone tell me why they are different and how the width of the switch transistors
affect the output voltage?FYI,the output load is a RC 10MHz filter.
../imgqa/eboard/Antenna/rf-mmcimhvklso.jpg

Thank you in advance,
Vasilis