How to reduce the first sidelobe level of microstrip antenna array

[chenchangfu]

I designed a 2X2 microstrip antenna array but the first sidelobe level was very high and the gain of the array was just 6dB.The patch element has the good radiation pattern and the gain is 4.5dB.I do not know the reason why the array has the low gain and so high sidelobe level.Can anyone tell me the details which affect the gain and the sidelobe?

 

[tyassin]

Hello,

Sidelobe level is dependent on the distance between elements. To reduce sidelobes try reducing element spacing or do some amplitude tapering. lower amplitude to the elements in the perimeter.
The gain reduction could be mutual coupling between elements. I do not know how the elements are feed, with phase and amplitude this could also influence the gain and sidelobes.

Regards

 

[eagle5]

A gain of 6dB for a 4x4 array is too low. You are probably making some mistake either in the array design or the simulation.
Could you tell a bit more about design parameters (spacing, feed distribution...) and the simulation software?

 

[chenchangfu]

Sorry,the array is 2X2.The spacing between elements is almost equal to a wavelength.The feed distribution is T power devider,the software is HFSS.I can give you the model,you can have a look and tell me the reason.

 

[chenchangfu]

OK,I will have a try.I can give you the model,if you have time you can have a look.

 

[tyassin]

Hi

A spacing of one wavelength will give sidelobes for sure.

 

[eagle5]

If the separation is almost 1 wavelength, what you are seeing are not sidelobes but grating lobes. This is probably the reason of high lateral lobes and low gain.
I would recommend you to reduce the distance to 0.7 lambda.

If you have still strange results you can verify the simulation by simulating independently the feed network and the array.
1. You can test the array by feeding each element with a lumped port and check the pattern. Remember to "edit sources" in order to assign the excitation value to each element.
2. You can test the feed network by replacing the antennas by port and check the magnitude and phase of the S-parameters.

 

[chenchangfu]

I also attempted to change the spacing to 0.7 lambda but it still did not work well.

---------- Post added at 14:21 ---------- Previous post was at 14:19 ----------

OK I will have a try as you said.

 

[chenchangfu]

I still can not get the good gain,many distances have been attempted but the result was not good.Now I do not how to do with the array.

 

[eagle5]

You can upload your file and we can take a look at it.

 

[chenchangfu]

OK,the model is uploaded.You can have a look and trouble you to find the question of the model.Thanks!

 

[ffidham]

you could use the Electronic Band GAp structures,
that's for the sidelobe suppression and also the backlobe reducing.