cst patch antenna

Hi All,
Dear freinds, i'm working on the paper alraedy published on MOTL on March 2006: "Integrated Antenna For Multiband Multi-National Wireless Combined With GSM1800/ PCS1900/IMT2000 _ EXTENSION".
I simulate this antenna by using CST Microwave Studio (Version 5), but i dont obtain the same graph of S11 parameter figured on the paper.
Please can you help me to resolve this problem (i dont know if this difference is due to the boundary or excitation ...).
Attached to this message you'll receive my CST project of the proposed antenna, and the related article.
Please, can any one retry this simulation by CST Version 5.
thank you very much.
bast regards.

Hi Simotic,

I made some small changes in your design:

1. The middle branch size was wrong: it would be 73 mm (you used 75 mm)
2. change metal thickness to 35um (not important though)
3. Dielectric loss tangent should be 0.02 (go to substrate properties and change it)
4. Use open (add space) to all directions
5. Use a bigger waveport (size can be: 4h x 5w where h is the height of the substrate and w is the thickness). Z_min of waveport starts from the ground metal: for 35um metal it starts from -1.555mm for your case.

changing above parameters and simulated in CST2008, following return loss is found (see picture). This is more or less the expected result.

Regards,
shameemkabir

ok dear shameemkabir,
i try it again by using your suggestions, i dont have the same graph as the article, bu the obtained S11 parameter are more accurate with respect to the measurement.
thank you very much for your help.
best regards.

sorry for asking this kind of quest.. but i'm a student and still new to antenna design.. i'd like to know whether Lg and Wg which is the width and length of the ground plane can be change in order to optimize the design or not.. what about the size of the patch that we had calculated before.. can we change the size .. in order to get the best result or we can just change the feed? plz help me..

Dear wanie84,
for antenna design, you can well change all dimensions of your antenna, but this affect the frequency of resonance of your antenna.
for the width of the feed line, you must to be careful in order to have Input impedance equal to 50 Ohms wich is compatible with much popular connectors.

tq for the answer.. really appreciate that..

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