Center tapping in ADS

u can use the center tapped tranformer and ignore the other primary winding

what exactly u want to do with it ?

khouly

you can choose a 1:1 balun and connect two node together the you get an idea inductor with center tap

I read in a paper that using a "2-to-1" inductor tap will improve the Q of the varactor by a factor of 4. I just want to test it.