query regarding gain and bandwidth of a Patch Antenna

[abhiinics]

Hello.
I am new to forum and hoping to get lots of help.
My question is that in many papers I have seen that by cutting slots in the patch you can enhance the gain but what is the mechanism behind that.? What happens to the antenna that it gives you enhance gain after cutting the slot.?
My same is for Bandwidth. In many paper the most common technique to get high bandwidth is to partial removal of ground plane so someone please throw some light on the reason of enhanced Bandwidth after partial removal of ground plane.
Thanks in Advance.

 

[vfone]

In fact as you cut the slot, the radiating patch area becomes lower, which reduces the antenna gain, bandwidth, and the return loss.
The position of the slot might change the patch polarization, and/or (due to breaking the surface current paths) to give multiple antenna resonances.

 

[abhiinics]

but I have seen in many papers that inserting the slot in patch increases the gain so I would like to know the reason behind that.

 

[vfone]

Is no reason behind that. Almost any change in the patch area (making smaller) and change in the surface currents paths, would decrease the bandwidth.
There is a possibility, to cut a slot and make a second resonance very close to the initial one, and in this way to make the total bandwidth larger. But this is an indirect way to increase the bandwidth.

 

[volker@muehlhaus]

but I have seen in many papers that inserting the slot in patch increases the gain

Can you give an example which paper says so?