lower gain of patch antenna

hi all,
i referred to a paper for a 2.4GHz patch antenna. however when i followed the design exactly i was not able to get the same gain or the freq. i am using hfss can someone tell me why is that happening.

i followed this paper http://www.ijafrc.org/Volume2/issue1/1.pdf

try an ieee paper...if you still face the problem let me know. In your design air box is defined under fr4 substrate. your design is not converged so increase the number of passes from 10 to 20 . i believe your excitation technique is wrong.

so i made an antenna which has gain of 1.6db. now suppose if i want to see the impact of body on this antenna. so now what i have done is that i made one more substrate and kept that below my ground (1mm,3mm,5mm). but i am seeing almost same response as if placing that substrate has no impact. also i have kept my radiation boundary such that it covers only the top half of the antenna (patch side) not the ground side below which the substrate has been kept.
am i doing this correctly. or do i need to change something.

First of all 1.6 dBi gain is very low try to match the impedance of the antenna ....the reason why you are getting the same response is due to the ground plane. The ground plane will not allow EM wave to pass through it. you can clearly see that in the radiation pattern. the lower hemisphere is consists of minor lobe compare to major lobe in the upper hemisphere that means no radiation along -z axis. In order to understand impact of human body on this antenna you have to create stack of differemt dielectri layers for example skin layer, fat layer, fluid layer etc..

Hi Sandeep,
thanks a lot for replying. wellactually i dont want to make an antenna. i just want to know what happens when an antenna is placed near body. now as you said since the lower hemisphere doesn't allow the impact to effect the antenna because of the ground plane.

1. so can i keep the substrate in the top half? if yes then should it be such that it's completely inside radiation boundary? so i will change the separation between the patch and the substrate . or do i need to change the radiation box as well?
2. body has many different dielectric values (fat,muscle etc) now just for simplification(just for start) i will keep the substrate ~81(water, a lot of water in the body).

so can i start with the above two assumptions.

1.yes, it should be completely inside the radiation box. you can place the fluid layer a few mm above the patch that will be fine. But always create a human phantom model to check the accurate effect.