Acceptable value for sidelobe levels in antenna arrays

[Henry797]

Hi Everyone,
Just wanted to ask experienced antenna engineers, what is the expected sidelobe level, as i've designed a 4-patch antenna array with 10.5dB realised gain, but sidelobe levels of 2.5dB. Do you think this is acceptable at 12-13 GHz frequency? If not, can you suggest some ways to reduce the sidelobe level in arrays?
Many Thanks
Henry797

 

[edf]

Hi Everyone,
Just wanted to ask experienced antenna engineers, what is the expected sidelobe level, as i've designed a 4-patch antenna array with 10.5dB realised gain, but sidelobe levels of 2.5dB. Do you think this is acceptable at 12-13 GHz frequency? If not, can you suggest some ways to reduce the sidelobe level in arrays?
Many Thanks
Henry797

With uniform (equal) power split for each patch, you should get sidelobes down 13dB. Make sure your patch input Zs all look alike.

 

[Henry797]

Hi edf,
Thanks for the reply. My antenna is well impedance matched, and both sides of my working plane look same, but its just the side lobes that I'm worried about. Since its a 4-patch microstrip antenna, is it normal that the antenna will have sidelobes that are high in magnitude. I mean my sidelobes ar 8dB down from the main lobe. But is that unacceptable, given that I wanted it to design for satellite application?

 

[edf]

Hi edf,
Thanks for the reply. My antenna is well impedance matched, and both sides of my working plane look same, but its just the side lobes that I'm worried about. Since its a 4-patch microstrip antenna, is it normal that the antenna will have sidelobes that are high in magnitude. I mean my sidelobes ar 8dB down from the main lobe. But is that unacceptable, given that I wanted it to design for satellite application?

If there are other satellite signal sources that might interfere with the desired one, your sidelobe level can definitely cause problems.

 

[Henry797]

Hi edf,
Do you have any suggestions on how to reduce the side lobe levels. I mean i'm not an expert in array antennas, but i'm assuming there must be a way to reduce the side lobes, ways like increasing the wide or length of the ground or substrate? Or may be the loss tangent of the substrate?
Regards
Henry797

 

[edf]

Hi edf,
Do you have any suggestions on how to reduce the side lobe levels. I mean i'm not an expert in array antennas, but i'm assuming there must be a way to reduce the side lobes, ways like increasing the wide or length of the ground or substrate? Or may be the loss tangent of the substrate?
Regards
Henry797

Typically your array element-to-element spacing should be less than 0.7 wavelengths and reducing the power to elements as you move away from the center will reduce sidelobes. With only 4 elements in your array, you're not going to reduce sidelobes significantly without losing most of your gain. What are the dimensions of your patches in wavelengths?

 

[Henry797]

The dimensions of my patches are L=0.2lamda; W=0.3lamda and I kept the spacing between elements at 0.5lamda. Should I try reducing the spacing further just to check?

 

[edf]

The dimensions of my patches are L=0.2lamda; W=0.3lamda and I kept the spacing between elements at 0.5lamda. Should I try reducing the spacing further just to check?

No, 0.5 is okay. For uniform power split, I calculate your sidelobes should be down 11dB. What is the overall size of your ground plane? Did you use a reference antenna to determine your gain?