Linear antenna array problem about spacing between elements

Hi guys, I am new to antenna design and currently enrolled at antenna course.
From my professor, I get this problem to solve.

Find spacing between elements of linear antenna array with binomial current distribution in order to achieve max possible gain with sidelobe level lesser then 30 dB.
Array must consist of 10 dipoles which longitude (L) is λ/10 and diameter of wire is r=L/30. Operating freq is 1 GHz.

So far I have searched through few books and i haven't found any equation for side lobe level of linear antenna array with binomial current distribution.
I am aware that this type of arrays do not have side lobes for spacing equal or less than λ/2, so spacing must be greater.

Does someone know where i can find equation(s) needed to solve this problem?

Thanks,
Dejan

Hello ND

i have spent a little bit of time looking for an answer to your question.sidelobelesser than 30dB=~ no sidelobe level

equation for directivity for a binomial array D=1.77*sqrt(N)=1.77*sqrt(10)=7.48dB

sidelobe's will be seen between a spacing of lambda/2 and 3 quarter of lambda.when the spacing increases beyond 3quarters of awavelength,sidelobe levels are actually higher than the desired lobe.




Regards
Chachito.

---------- Post added at 15:17 ---------- Previous post was at 15:00 ----------

i have a matlab file,where you could actually look up the sidelobelevels for various interelement spacing? would you be interested?

Regards
Chachito.

Hi Chachito,

I am aware of equation you wrote. (Balanis's book around 330th page).
On next page there is graph from which is possible to anticipate that spacing must be between λ/2 and 3λ/4.

Anyway, thank you for your time.

Best regards,
Dejan

for the matlab file, the value for d is in what unit? is it m, cm or mm?