parameters required for patch antenna for 100MHz

hi everybody i am doing work on patch antenna for 100MHz using shorting wall and U slot to reduce the size of patch but keeping the radiation box lambda/4 i get very low radiated power so gain and efficiency are also low, here i am attachming my design , please any one look at this and help me out for improving my antenna parameters...my email id is engineermohsinali@gmail.com
thanks

I had a quick look. your radiation box only extends upwards. your antenna should be in the centre. I believe the radiation box is seen as a perfect conductor. this is probably why it doesn't work.

thanks man , if put antenna in the middle then it gives error of port refinement and i have assigned the air box as radiation , can you please tell me more about this

---------- Post added at 08:47 ---------- Previous post was at 07:46 ----------

this error comes when i put antenna in middle


HFSSDesign1 (DrivenModal)
[warning] Boundary 'PerfE1' is an infinite ground but does not touch a radiation surface. (12:50:24 PM Apr 19, 2012)
[error] Port refinement, process hf3d error: Port port1 is assigned to an internal face. Only allowed with lumped ports.. (12:50:30 PM Apr 19, 2012)
[error] Simulation completed with execution error on server: Local Machine. (12:50:30 PM Apr 19, 2012)

for the first warning: either extend the ground plane or define is as a finite perfect conductor rather than an infinite gnd.

I think you are using a wave port needs to be backed by a conductor. You can solve this by putting a cap on the back of the port or using a lumped port if the port needs to be embedded in dielectric.
Look at some examples that come with HFSS or the manual. the antenna design kit (which is free) will also help you see how things need to be set up.

yes this problem is now fixed but still i am not getting the correct results. can you please check my design weather it is correct or not ? i am very much worried for this why my results are not coming.....thanks

can you upload the new project file?

thanks man, infact i am using radiation boundary lambda/4 on either side except downward , i tried many other examples for ISM band (2.45 GHz) there i get fine results but when extend my design and shift my frequency on 100 MHz all the results become wrong , u please do some favour for me just do something with the design and bring gain and directivity more than one and efficiency greater than 50% , it will be enough for me , as i tried many thing on this but i could not get right results , please i will be very thankful for you and also i am uploading my changed project file please in which i have made the ground plane finite conductor , check it please.....

mkonca please apply your skills of HFSS and help me ,

i have also tried this kind of design using lump port but here still i am getting correct results, in this design i am not using shorting wall

So far, I had a look at the first file. there are some mistakes.

-First of all, you needed to extend the radiation boundary down. you didn't.
-The sweep setup was inappropriate. you cannot sweep from 1Mhz using fast sweep. the simulation will take a very long time. This is equivalent to simulating an antenna that works at 100 Ghz from 1 GHz.
-You did not place a cap at the back of your wave port.
-there is no need to use a box for the shorting plane. it will take more time and give the same result as a 2d rectangle.
-outer side of the coax needed to be a conductor.
-take my advice and download the antenna design kit for hfss. its free. you can see how the feeds are made there.

I simulated after some modifications and it resonates at 100 mhz but the S11 is too high(-3.5 dB). I dont have the time to improve it further. I am attaching the file. Try to move the feed point or change other parameters to get a better match and it should work.

thanks a lot man for your kind cooperation , following are the errors come when i simulate the project you have uploaded

HFSSDesign1 (DrivenModal)
[error] Out of memory (11:43:26 AM Apr 25, 2012)
[error] Simulation completed with execution error on server: Local Machine. (11:43:26 AM Apr 25, 2012)
please help me whats the reason as i also reduce the sweep ranges from 80MHz to 120MHz but still these errors come

---------- Post added at 07:45 ---------- Previous post was at 07:44 ----------

i am using the full system memory for HFSS

this means you don't have enough RAM to run the simulation.

if this happens before the adaptive run converges it will be hard to fix.
if you get this error when the fast sweep starts, try to use interpolation or discrete sweep (most ram efficient)

it comes before adaptive run converges but i have assigned 2.5Gb of RAM out out of 3Gb to HFSS then why it shows this error? adaptive run goes to 37 passes and then it shows this error

dear mkonca sorry as i am taking your too much time but infact very much worried about my project i have simulated my design under the changes you have made in the design uploaded by you. my S11 are very perfect i.e. -21dB for the reference i am attaching S11 graph and antenna parameters snap shot to discuss you i am getting incident power 99% that means matching is perfect but why the radiated power is too low, please check this and also tell me that how can i improve bandwidth as i used several bandwidth enhancement techniques but the bandwidth remains the same very small almost 2% of central frequency also i am uploading the changed design

I think you forgot to define the integration line on the port. I was simulating but I have to go now. so try it. I will let you know about my result tomorrow.

---------- Post added at 17:47 ---------- Previous post was at 17:45 ----------

also try. setup-options-enable iterative solver. it required less ram with this option for me.

---------- Post added at 17:50 ---------- Previous post was at 17:47 ----------

I can confirm that the radiation efficiency went up. the integration line was the problem. I can't believe it even worked without it. :)

now i have also define integration line on the port but still not enough radiated power and radiation efficiency although accepted power is 99% , whats the problem there i can't understand this, can u please?

sorry man I was in a hurry and checked the parameters in another open project. it doesn't work for some reason. may be there is something wrong in the setup that we are missing. make an antenna using the antenna design kit and let it create the model for you in hfss. then you can change the top layer with your design. this way you will know that your setup is right.

design kit will make an antenna for 100MHz in original dimensions but i need reduced size antenna for 100MHz

yes of course. you can modify it. it will be easy to copy some parts from your design into the new project. just try to keep the port setup but you can move things where you want.