In MIMO, angle of arrival is important to align all the received signals before detection or demodulation.

Dear Ahmad,

Far distant located planes are not always at zero shifts due to uncontrollable modus operandi conditions for long duration.

Best wishes 

Dear Mr, AR Reddy,

Yes of course it is. But what about calibration issues ?

Dear Mr. Dwivedi,

I have never heard of uncontrollable modus operandi, could you share a simple document here ?

Thank you very much

Dear Mr. Chi,

Yes this is why we calibrate, i.e. align all phases together so that relative phases between sensors are zero. But my question is what are the reasons of phase misalignments between antennas other than errors in displacement of antennas and ambient noise ?

Thank you very much

Dear Ahmad! Errors in estimation of bearing arise because of differences between amplitudes and phase characteristics of the input circuits of receivers and multipath processed signals. Errors in the antenna positions, their mutual influence and the imperfection of their radiation patterns affect the bearing accuracy. If You have other suggestions, please share these assumptions with us. All the best.