de-embedding device leads from measured s-parameters of the device

I am designing an amplifier at 12 GHz,using infineon
Cfy25 device.

Vendor supplied s-param were extracted in following
Manner,using FR4 board.

Note: reference plane position at device lead end,
Leads are 1.1mm long

Since I am using another substrate,Alumina,I need
S-param ,at the package end ,as shown below

I simulated the device leads separately and used ADS
De-embbeding boxes as shown below and extract DUT s-param
Experts please look into this and give your valuable suggestions,to solve this issue.

Because I do not know how ADS deals with s-param
De-embedding,whether it transforms to T parameters
And

But this method did not work, the resulting s-param
Were totally changed,not usable as leads should change little phase and magnitude of s-param,not the entire frequency response itself.

For de-embedding we use following matrix relation
Using transmission parametets

Maybe you have seen this already, but still:
http://www.microwaves101.com/encyclo...ference-planes

Thanks terminator,
Its fantastic example,to understand de-embedding.

Hard to believe that Infineon extracted S-parameters at 12GHz using FR4.