SLL problems in a large phased array antenna

Hi!

I have designed a phased array antenna using Matlab's Phased array tool box and I have few doubts regarding the same.

1) While simulating an 8X8 array with uniform distrubition, the values obtained for SLL and Power were matching to that of theoritical calculations (say -13dB SLL etc.,).

But, when i make the array larger (say roughly 5000+ elements), my SLL is going down to '-18dB' with the same uniform excitation. Is it a limitation of Toolbox (or) that is the closest value to practical observation? Please explain.

2) I have tried applying Taylor tapering(windowing) to my larger array discussed in the previous problem. Here, I couldn't notice any difference in the max power obtained at the boresight with changing order(nbar) of the taylor window. But, there should be a slight variation as per the theory. Could someone please explain?

Thanks & Regards, Sricharan, Deputy Engineer, Bharat Electronics Limited, Email:[e-mail]

Answer 1

[Honglei Chen]

Hi Sricharan,

Could you share a bit more info how you determine the SLL, is it by looking the beam pattern plotted in the figure. If so, you may need to use a finer grid when plotting, otherwise, for a 5000+ element array, the default one degree grid is too loose to accurately represent the beam pattern.

HTH

[Sricharan Chadram]

Hi Chen,

Thanks for your comment. Actually, I am using the 'pattern' object of phased array toolbox to plot the beam pattern & I couldn't find any option to specify the grid settings for the plot. So, I have chosen default settings only. Could you please assist me in how to choose finer grid for this case? Currently. I am adding a custom data tip with mouse positioned at -3dB value for calculating the beamwidth. Kindly refer to lines 9 to 12 of the attached script 'Large_Array.m'

Thanks & Regards, Sricharan Ch, Dy Engineer, D&E-R&FCS/NS, Bharat Electronics Limited.

[Honglei Chen]

Hi Sricharan,

For example, in your call to plot pattern, you did

pattern(hura,freq,-45:45,[-45:45],'PropagationSpeed',c,... 'CoordinateSystem','rectangular',... 'Type','powerdb',... 'Normalize',false)

The first -45:45 is azimuth grid and the second -45:45 is elevation grid. Therefore, if you want a finer grid, you can try things like -45:0.1:45. However, if you want to measure beamwidth, it might be easier to plot in cuts. For example, if you want the azimuth cut, you can do

pattern(hura,freq,-45:0.1:45,0,'PropagationSpeed',c,... 'CoordinateSystem','rectangular',... 'Type','powerdb',... 'Normalize',false)

HTH