According to literature it is said that by adding slot,notches or using fractal shapes we can obtain multibands. i have tried but none of them is working.
Yes slots, fractals,etc can be used to obtain multi-bands for a microstrip patch antenna. But the thing is that, they are to be positioned properly on the patch, depending upon which higher mode u want to excite. If this goes correct along with proper feeding, then u may achieve a proper result.