1. A wide-band array antenna comprising: N×M antenna elements, and multipliers connected to each said antenna element, each having a real-valued coefficient, wherein assuming that said elements are placed at distances of d 1 and d 2 in the directions of N and M, respectively, the coefficient of each multiplier is C nm, and by defining two variables as v&equals;&ohgr;d 1 sin &thgr;/c, and u&equals;&ohgr;d 2 cos &thgr;/c, the response of said array antenna can be given as: 19 H &af; ( u, υ ) = &Sum; n = 1 N &it; &Sum; m = 1 M &it; C nm &it; &ee; j &af; ( n - 1 ) &it; υ &it; &ee; - j &af; ( m - 1 ) &it; u ( 5 ) by appropriately selecting points (u 0l, v 0l ) on the u-v plane according to a predetermined angle of beam pattern and the center frequency of a predetermined frequency band, the elements b, of an auxiliary vector B&equals;&lsqb;b 1, b 2,..., b L &rsqb;(L<<N×M) can be calculated and the coefficient C nm of each said multiplier corresponding to each antenna element can be calculated as follows 20 C nm = &Sum; l = 1 L &it; G a - 1 &it; b l &it; &ee; - j &af; ( n - 1 ) &it; υ 0 l &it; &ee; j &af; ( m - 1 ) &it; u 0 l ( 17 )