"Blind spots" is a well known phenomena occuring in the operation of the phased array "blind spots" means total reflection of input power Either of two conditions leads to total reflection

null of the radiation resistance or infinity of the admittance. This paper is to investigate these conditions. Through detail mathematical analysis

it is concluded that the null of the radiation is the only reason to cause total reflection i.e. ’’blind spots" . Besides

approximate conditions for existence of the null of the radiation resistance are give. We have also obtained some results different from those published in foreign literatures.