1. A wide-band array antenna comprising: N×M antenna elements arranged for receiving and transmitting signals according to the wide band code division multiple access (WCDMA) communication system, and a plurality of multipliers, one multiplier connected to each said antenna element, and each multiplier having a real-valued coefficient, wherein when said antenna elements are placed at distances of d 1 and d 2 in directions of N and M, respectively, the real-valued coefficient of each multiplier is C nm , and by defining two variables as v=ωd 1 sin θ/c, and u=ωd 2 cos θ/c, the response of said wide-band array antenna can be given as: H ⁡ ( u , v ) = ∑ n = 1 N ⁢ ∑ m = 1 M ⁢ C nm ⁢ ⅇ j ⁡ ( n - 1 ) ⁢ v ⁢ ⅇ - j ⁡ ( m - 1 ) ⁢ u ( 5 ) by selecting points (u 0l , v 0l ) on a u-v plane according to a predetermined angle of beam pattern and a center frequency of a predetermined frequency band for use in the WCDMA communication system, elements b l of an auxiliary vector B=(L<<N×M) are calculated and the coefficient C nm of each said multiplier corresponding to each antenna element is calculated as C ⁡ ( n , m ) = ∑ l = 1 L ⁢ G a - 1 ⁢ b l ⁢ ⅇ - j ⁡ ( n - 1 ) ⁢ v 0 ⁢ l ⁢ ⅇ j ⁡ ( m - 1 ) ⁢ u 0 ⁢ l ( 17 )