Shorted-Post circular microstrip antenna

时间：03-31 整理：3721RD 点击：

Hi Guys,

I'm designing Shorted-Post circular microstrip antenna at fr=2.45 GHz with Er=3.55 FR4 and h=1.5mm.The metal is gold with thickness t= 0.018 mm. The position of short post is in the center of microstrip and the feed is shifted from the center by 4.4mm. I'm using Sonnet suite v12.56 to design and simulate this antenna. After simulating, I have found high return loss and I don't know the problem. I need your help to find out the error in the design of this antenna.

I have attached the sonnet file of the designed antenna.

Thanks in advance

Hello,

I wonder if your model is missing an air layer below the substrate?

Best regards
Volker

I have already added an air layer below the substrate but I found the results more worse than now.....
Concerning to the short pin, Is it the same via structure in sonnet software? I'm asking about that because I have seen that the via structure is a tube i.e it is not solid! So is it right to represent the via in the sonnet software as short pin?

Ok, I think I know what is wrong
There is a misunderstand with the way how the via port works.

I assume that the circular shape on the GND layer should be the back side metalization for the antenna? If yes, then the via port must be drawn between these two circular shapes, and you must remove the cutout on the bottom shape. The via port must be between the metals.

I have made this change and results look correct now.
Attached is a *.ZON packed project with results. Import in the Sonnet editor with File > Import > packed Project
Please check if this is the layout that you wanted to simulate.

Best regards
Volker

Dear Raid,

the cell size is determined by the smallest geometry detail ("geometry sampling"), this is not critical for your antenna.

The box size was an educated guess, I wanted to push the metal side walls a little bit away from the antenna. Your box seemed a little bit close, and this could change the currents on the antenna -> input impedance and radiation patterns.

The total height of air layer above and below should be less than lambda/2 at the highest analysis frequency. This is to avoid box modes in the analysis box.

Best regards

Volker

Added after 1 hours 1 minutes:

Hello again Raid,

I have attached a screenshot of the antenna model, the current density at resonance (2.48GHz) and the antenna gain.

Best regards
Volker