I need a new pach antenna with 12 GHz bandwith

think abt uwb antennas

the simple answer is to go way up in frequency. Patches typically are narrow band, 10 to 20 percent.

Just design a patch at 120 GHz and you will have the 12 GHz bandwidth.

Getting wider bandwidths at lower frequencies is where thisngs get hard.

My real thought is that you need to provide a more complete description of your application to get meaningful suggestions.