u slot patch antennas

May I know what are other antennas beside u slot patch antennas are small in size compared to a patch? I am looking into antenna miniaturisation and would like to hear some opinions and pointers in this area.

for which frequency range should the antenna be? I had once a project about small microwave patch antennas.

hye i also work on microstrip patch antenna using U-slot but i dont know how to calculate the feed. do you have any ideal to help me