Some Curious Results of Array Investigation L. Kogan National Radio AstronomyObservatory Socorro, NM USA

I. Level of Negative Side Lobes at PSF does not depend on the array configuration and is determined completely by the number of the array antennas N!!! 22 July 2011 Moscow

22 July 2011 Moscow

II.Tapering may not reduce sidelobes. The dish antenna theory: Tapering of the current distribution at the apperture leads to the side lobes decrease. This statement may not be true at the case of the arrays. Tapering is multiplication of the UV coverage with the tapering function. So at the image plane, it leads to the convolution of the untapered beam pattern with the Fourier transform of the tapering function. The convolution leads to the broadening of the main beam as well of the sidelobes. But the level of sidelobes may not be reduced, if the distance between the sidelobes is bigger than the width of the Fourier transform of the tapering function 22 July 2011 Moscow

22 July 2011 Moscow

22 July 2011 Moscow

III. If we want to change the value of the PSF at the given direction, then all antennas of the array should be moved toward the same direction! lelss 22 July 2011 Moscow

22 July 2011 Moscow

IV. The shape of the phased array beam pattern is identical for any phased direction, if the direction cosine coordinates are used ! 22 July 2011 Moscow

22 July 2011 Moscow

22 July 2011 Moscow