hilbert antenna..is airbox ok?how can i make it more broadband?...

MrHfss · Feb 6, 2013

can someone please help me?...

1)check if airbox size is ok

2)i am changing the size of some parts (for example A2m from 16mm to 20mm)and i am trying to archieve s11<10db and gain >0db for 2.4GHz(wifi) and 1.92-2.17GHz(umts) (and 1.71-1.88(gsm 1800)if it is possible)

how can i make my antenna more broadband to archieve this?

thank you for your time....

(i am using hfss v.12 and you can unzip the file ,open hfss and then tools->run script)

jeeudr · Feb 9, 2013

I tried running your script in HFSS 14.0 (running on windows 7) and it crashed.

I can attempt to answer your first question for the airbox size. as a rule of thumb, keep your airbox boundary at least lambda/4 away from the radiating structure. for a broadband antenna, this lambda would correspond to your lowest operating frequency.

MrHfss · Feb 9, 2013

my lowest operating frequency is 1.7Ghz so lambda/4 =44.117mm

44.117mm from patch (B) or 44.117 from ground (A)?

also i have to expand the airbox 44.117 to left and to the right etc?

i uploaded again hilbert antenna.hfss ....you can run it if you want with double click...i hope it will work to your computer...(maybe it is locked for some reason)...

thank you for your response...

jeeudr · Feb 9, 2013

I meant the distance from the top of the patch (B) to the top face of the airbox.

Also, I normally increase the X and Y size of the airbox to the same distance as well.

MrHfss · Feb 9, 2013

if i dont increase the X and Y size of the airbox to the same distance as well it is a mistake?

because when i try it i think the results is not so logical...

can you please try to do that for me....maybe i am doing something wrong...

thank you again...

jeeudr · Feb 9, 2013

I tried the script a couple of times, and have not been able to get it to work for me.

If you upload a .hfss file, I can check it out.

MrHfss · Feb 9, 2013

hilbert antenna.hfss

i hope it will work to your computer...(maybe it is locked for some reason)...

jeeudr · Feb 9, 2013

your most recent attachment also only has the .vbs script file. I tried it again and it does not work with HFSS v14.0 .

MrHfss · Feb 9, 2013

sorry my mistake...i think now is 1.hfss

jeeudr · Feb 9, 2013

i found quite a few concerns in the setup that you have made.

1. you can use a teflon material for the gap between the inner and outer of the coax
2. you should have the pin extension of the coax only within the substrate and not outside
3. i do not see the purpose of an extra PEC box1 and the vaccuum box2 between box1 and substrate. do you want it as a reflector to your patch antenna ? (there is very little backward radiation from a patch)
4. if you fractal pattern is on the top of the substrate, then is the bottom face of the substrate is usually a ground plane and connected to outer of coax
5. you can use a planar sheet for the fractal pattern, the accuracy is usually still good.

(there maybe a few more that I might have missed)

I have copied your fractal pattern and placed it into one of my own setups for patch antennas. the file is attached. You should try simulating it.

MrHfss · Feb 9, 2013

''1. you can use a teflon material for the gap between the inner and outer of the coax''

οk

''2. you should have the pin extension of the coax only within the substrate and not outside''

this change my results?

''3. i do not see the purpose of an extra PEC box1 and the vaccuum box2 between box1 and substrate. do you want it as a reflector to your patch antenna ? (there is very little backward radiation from a patch)''

so i will keep the infinite ground as ground...i will remove pec box 1...vaccuum box2 is to increase bandwidth
if i use pec box 1 for ground and remove infinte ground the results will be more close to reality?

''4. if you fractal pattern is on the top of the substrate, then is the bottom face of the substrate is usually a ground plane and connected to outer of coax''

''5. you can use a planar sheet for the fractal pattern, the accuracy is usually still good.''
ok

thank you sooo much for your time and knowledge!!
i am using hfss v12.1...i cant open you file because you are using v14...can you save it with a diferrent way so i can open it...

jeeudr · Feb 9, 2013

- current travels in the inner conductor of the coax and return path is along the outer braid/shield. if you just extend the inner alone (without any connection for the outer), then it will not be that effective. (there are some exceptions to this, but not applicable for this patch antenna)

- I would advise to remove box1. to be closer to reality, do not use infinite ground. rather just draw a rectangular sheet on the bottom face of the substrate and assign it a Perfect E boundary condition. also remember to subtract this face and the coax connections.

I am sorry, but there is no option for me to save a backward compatible version of the file. however, you can try to import the 3D model that I have exported. create a new project -> insert design. then modeler->import->Ansoft 3D modeler file (.sm3 file) v.21

I have also attached 2 screenshots which might be helpful.

MrHfss · Feb 9, 2013

1)i should subtract bottom face(ground) with outer face of coax (outer braid/shield)(what material i should put to outer face of coax?pec?or just a cylinder with perfect E) ?

2)also how long should be the coax outside the patch ?

3)i will try to find hfssv14 to see your file

4)if a use a planar sheet for the fractal patter (instead of copper) i have to choose perfect E or finite conductivity for this?

again thank you veeery much!you helped me very much!!!

jeeudr · Feb 9, 2013

1)i should subtract bottom face(ground) with outer face of coax (outer braid/shield)(what material i should put to outer face of coax?pec?or just a cylinder with perfect E) ?

i. Draw a large cylinder of Teflon to represent the entire coax
ii. Draw a smaller concentric cylinder of PEC to represent the inner core
iii. clone & subtract ii from i
iv. apply Perf E boundary to outer surface of i
thats all

2)also how long should be the coax outside the patch ?

any length should be fine. it should not affect the results of your simulation. a wave port is treated as coming from an infinitely long waveguide (that is why either a PEC endcap is used (or) it is usually placed at the edge of the model).

3)i will try to find hfssv14 to see your file

4)if a use a planar sheet for the fractal patter (instead of copper) i have to choose perfect E or finite conductivity for this?

Perfect E will simulate faster than finite conductivity. both results should be very close to each other.

MrHfss · Feb 9, 2013

''iv. apply Perf E boundary to outer surface of i''

to apply PErf E to outer surface of i, i choose teflon and assign boundary->perfect E

or is another way to apply perfect E only to outer surface of teflon?

jeeudr · Feb 10, 2013

MrHfss said:
''iv. apply Perf E boundary to outer surface of i''

to apply PErf E to outer surface of i, i choose teflon and assign boundary->perfect E

or is another way to apply perfect E only to outer surface of teflon?

Edit -> Select -> Faces -> Left-click on outer surface of the outer (Teflon) cylinder to make selection . Then you can apply the Perfect E boundary condition only to this selection.

MrHfss · Feb 10, 2013

thank you!!!

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