Double ridged horn antenna

Hi, i've in mind to make by my self a double ridged horn antennna (for 2GHz an above), anyone know some open project with dimension or similar?
This kind of antenna is much expancive for me because it is patented?

thanks any suggestion will be much apreciated.
matteo

I find the patents (US20050078044) it's very exaustive, with dimension and more but sfortunatly it is dated april 2005 so it is still valid!

Thanks to everyone!