Reconfigurable slot antenna design

Hi all,

Currently I'm designing reconfigurable slot antenna, from what I've read, slot antenna could produce omnidirectional radiation pattern, but from my design, the radiation pattern is directional. How can I get omnidirectional pattern? Does changing the slot design affect the radiation pattern?
I've design the feed by using microstrip transmission line at the back of the ground plane positioned at the centre. Also, may I know if there is any formula that I could calculate for the length of the transmission line? As I only found the formula for the width which is for 50 ohm impedance.
I hope someone can help me in this matter. Thanks in advance :)

hi
slot antenna usually applied for directional antenna and i thick if u seen for omnidirectional that work at lower frequency