Problems with the gain of my array

Hi everybody!

I'm new here, I'm finishing my studies, so I have to do a final project.

In one of my stages I have to built a array of microstrip patch antennas fed by coaxial wire (fed probe).

But after the design and simulation of the antennas in HFSS I realized that I have a problem.

The problem is that the total gain of my array is more or less the same of a single antenna of the same type.

To know how to simulate a fed probe patch antenna I installed the HFSS- antenna Design Kit to build the antenna in a HFSS environment and I also follow this tutorial:

-http://pt.scribd.com/doc/17748492/Hfss-Full-Book.

I also read that the array space between the antenna elements must be less than a half wavelength, but this wavelength is in a free space or in the microstrip?

I will put here my projecto to someone could see if I did anything wrong in the implementation of the array!

Please try to help me beacuse I don´t have to much time to end it.

Best regards,

Rodolfo

If you post your files compressed with zip, gzip, bz2, p7z or any other compression algorithm which is public, I will look at your files. But I refuse to open rar files unless I really have to, since the compression algorithm is not public. (It's just one of my policies!)

When the antennas are close, you will get coupling between them, so their characteristics will change. I would attempt to simulate it as as two individual antennas, ignoring any power splitter you may have. Then add that later.

I believe the sepparation can be smaller than the free space value due to the dielectric, but I must admit, I am not sure about this. I thought that was so, but then my next point about capture area makes me wonder if this is true.

I don't believe the spacing needs to be less than lambda/2. If it is too close, you wont get any gain. You want the capture areas of the two antennas to just touch. Theoretically, at least in free space, the array factor will tell you the gain. But in practice, if the antennas are close, their presence will effect each other, whereas the array factor is derried by assuming the antennas are isotropic radiators.

Sorry I can't be more help. I'm no expert, but I try to help. If I'm wrong on anything, I'm sure someone will correct me, and we will both learn.

Deborah

Sorry I didn´t know that, I will try to post again with other compression algorithm. Yes, I know that there is a relation between the mutual coupling effect and the grating lobes. I already tried to increase the distance between antennas, but the the total gain doesn´t increase , my doubt is if I´m simulating in a proper way.

Regards,

Rodolfo

I looked at your HFSS file and can see that you have an excitation of 1 V on coax_pin_T1, but 0 V on all other ports. Needless to say, if you don't excite the other ports, the antenna gain will not change much - only mutual coupling effects will come into play.

On the HFSS menus, click "HFSS", then "Fields" and finally "Edit sources". There you can enter a different excitation. Set them all equal to 1 V at an angle of 0 degrees, and you are effectively feeding them all in phase. When I set them all to 1.0, the gain jumps from 5.9 dBi to 12.2 dBi. Note these are post-processing changes, so there's no need to rerun the simulation.

I've attached a revised version, which allows you to adjust the values of the voltages from the optimetrics by tuning. So you can see the changes in real time, as you move the sliders up or down. Note this has been edited with HFSS 14.0, so it may or may not be read ok by HFSS 13. But I don't think it makes use of anything new to HFSS 14, so you should be ok.

I'm not sure if you will need an Optimetrics license to use the tuning - hopefully not, but it might do. Anyway, the main point is you needed to edit the sources so all 4 of your antennas were excited, not just one of them.

I hope that's helpful to you.



Deborah

Thank you very much Debora Harry! I have already solved my problem because of you!

Regards,

Rodolfo