Radiation Pattern not symmetrical

[samruddhathakur]

Hi,
I have designed and simulated a microstrip Patch Antenna Array (4x4) in HFSS but the radiation pattern achieved is not symmetrical. Can any one tell me how to achieve symmetrical pattern.
The spacing between all the Patches is contant 0.8 times wavelength.. I am ataching the image

 

[samruddhathakur]

Can anyone tell me methods to reduce the sidelobes in the above image..

 

[RF_Jim]

Hi,
I have designed and simulated a microstrip Patch Antenna Array (4x4) in HFSS but the radiation pattern achieved is not symmetrical. Can any one tell me how to achieve symmetrical pattern.
The spacing between all the Patches is contant 0.8 times wavelength.. I am ataching the image

Since one must assume your 4x4 patch array is drawn all properly symmetric, it is a safe assumption that un-intended effects such as feedline/strip-line/micro-strip radiation is taking place to affect the radiation pattern.

This is where RF designers earn their pay: proper attention to layout and Z matching of lines so as to prevent 'standing waves' on the RF distribution and phasing lines which can contribute to additional radiated RF energy ... one might try some 'adjustments' (play some games) on the interconnecting RF lines and note the effect. This can be a somewhat time-consuming activity, but this is what real-life sometimes presents to actual designs and designers.

RF_Jim

 

[samruddhathakur]

Hello Jim, thanks for the reply. Do you think mitering a strip line at bends will reduce the sidelobes ?? If so, is their any specific formula for it i mean how much should i chamfer??

 

[chameleon]

I think your main problem is not the symmetry but the patterns having high sidelobes. Your sidelobes are most likely due to array factor. You should try a small spacing between your elements, say lambda/2 or slightly smaller.

 

[KRISz]

:shock::shock:

 

[samruddhathakur]

Hello Chameleon, thanks for reply.
I didnt realy understood what you said about the arrayfactor responsible for my sidelobes,can you plz elaborate..
My antenna structure is full planar so its difficult for me to reduce the distance between the patch as they come very close to the feed lines, so is their any other method to achieve it??

 

[chameleon]

In an antenna array, the overall pattern is the multiplication of the element pattern and array factor. Even if your single patch element does not have any sidelobes (which may be the case if it's a conventional patch) your array factor WILL have sidelobes if center to center spacing between your elements exceeds lambda/2. How do you feed your elements? I don't see why you cannot move elements closer because of the feed lines.

 

[samruddhathakur]

Hi, i really appreciate for your reply.
Here is a glance of my array . So if i move my patches closer they might couple with my Feed line. So is there any other way of reducing sidelobes without changing the distance between the Patch. I found out that amplitude tapering might solve this problem. Can you guide me..

 

[chameleon]

Just give it a shot, reduce your spacing a little. You'll (or you should) see those sidelobes moving outwards. For a while, I don't think coupling will be strong. If you find out that the coupling is strong, I advise you to change your feeding scheme.
For this case tapering will not help you that much. You'll lose aperture efficiency (your gain will drop), you may observe slight improvements in the sidelobes, but they won't go away.

 

[samruddhathakur]

Alright, i will give it a shot.
Thanks again..

 

[yogaramesh]

Hi Everyone ....
Now i am try to do this model attached in file. but i don't know how to specify the cone wide and long ... please help me regarding this