Question about the change of Directivity in Phased Arrays

[Lupin]

Array Antenna Question

Dear RF people,
I want to ask a question about Phased Arrays:
A linear array configuration of equispaced uniformly excited isotropic elements is given. The Directivity is D1 dB.
If I replace the isotropic elements with antennas (e.g. patch antennas) whose radiaton pattern is cos(Teta) for -90°< Teta <90°, 0 elsewhere, (for every fi-cut) how much is the Directivity D2 of the new array?

D1>D2?
D1<D2?

Best regards
Lupin

 

[tapa]

Re: Array Antenna Question

If the radiation patter of an antenna is cos(Teta) normaly it means that the directivity is >1, so use tu be A*cos(Teta) with A>1...

All non omnidirectional antena has a directibity > 1

So D1<D2.

 

[Lupin]

Re: Array Antenna Question

OK,
so it means that, starting from an isotropic element, if I reduce the Field for Teta > +60 (e.g.) and Teta < -60° the overall array configuration Gain will decrease....

I want to know deeper another topic. In first approxination, Array Directivity in Squint conditions (e.g. +30°) is equal to Directivity in Broadside condition - 10 * log10 (cos(30))... so Dir(Broadside) - 0.62 dB
isn't it?

Regards
Lupin