EBG structures and number of cells

[shahid78]

in EBG structures we have periodic arrangement of some particular shape . for example in mushroom type EBG we have periodic arrangement of square patches with vias. and each mushroom with via form one cell of EBG structure
my question is how many such repeated mushrooms (cells) do we need for any practical antenna design?
and how the number of mushrooms effect the performance parameters of antenna?


regards

 

[Mustafa_Engineer]

I will answer your question.

first you start with one raw for instance....and check your results...the put another raw and check it again...and so on.



Mustafa

 

[prafuldeo]

hello shahid..
as a thumb of rule always make the total size of your EBG ground plane greater than 1.1 lambda. As we determine the reflection phase of EBG unit cell considering it as infinite, more the number of cells, closer it will give results to simulated one. I've tried to go below 1.1 lambda but results then started changing. So keep the EBG ground plane > 1.1 lambda.. Hope it helps..

Regards
Praful

 

[shahid78]

hi Praful

thanks for your answer. but still some doubts .
you mentioned that EBG ground plane size should be at least 1.1* lambda. which lambda yuor are talking about ? free space wavelength or guided wavelength?

also i think this 1.1* lambda ground size is too large for EBG because one advantage of using EBG is to decrease the ground plane size.

the rule of thumb which you mentioned is valid for PEC ground plane


regards
shahid

 

[prafuldeo]

hello shahid..
lambda is free space wavelength. if you want to have smaller ground plane then you have to do check it by changing parameters. it is very difficult to perdict the nature of EBG if the ground plane is smaller than lambda....

Regards
Praful

 

[prafuldeo]

hello sahid.. i was just wondering have you found any means to reduce the size of EBG ground plane. I am also looking for some thing which help to reduce the size. The problem is as soon as we reduce the EBG ground size, return loss messed up. let me know if you find out something.. cheers

 

[prafuldeo]

hello shahid,
Have you been successful in finding the solution to reduce the size of EBG ground plane? Once we reduce the size, S11 is affected too as well as sidelobes gets more pronounced..

 

[shahid78]

hi prafuldeo

well i am also still doing some simulations to reach to any conclusion.
but i agree with you as you decrease the size of the ground plane , it will affect the return loss and side lobes, however the size required for EBG ground plane should be less than the PEC ground plane for the same performance

i hope to find some valid conclusions regarding this issue in future or may be someone else may post their comments to resolve this problem

regards