Circular antenna array design is one of the most important electromagnetic optimization problems of current interest. The problem of designing a large multiple concentric planar thinned circular ring arrays of uniformly excited isotropic antennas is considered inthis paper. This antenna must generate a pencil beam pattern in the vertical plane along with minimized side lobe level (SLL). In this paper, we present an optimization method based on an improved variant of one of the most powerful real parameter optimizers of current interest, called Differential Evolution (DE). Two sets of different cases have been studied here. First set deals with thinned array design with the goal to achieve number of switched off elements equal to 220 or more.The other set contains design of array while maintaining side lobe level (SLL) below a fixed value. Both set contains two types of design, one with uniform inter-element spacing fixed at 0.5λ and the other withoptimum uniform inter-element spacing. The half-power beam width of the synthesized pattern is attempted to maintain fixed at the value equal to that of a fully populated array with uniform spacing of 0.5λ. Simulation results of the designed thinned arrays are compared with a fully populated array for all the cases to illustrate the effectiveness of our proposed method..