how to design the PAD in a MMIC?

Hello my friends,

I am wondering how to reduce the impact from PADs in a MMIC design.

I find when I complete all layouts without Pads, I can achieve very good VSWR. However, after I add the pads, the response deteriorates and the central frequency move several GHz. I have tried many sizes of PADs and have no good results.

Is there any trick in these pads design?