In this paper, a simulation-based optimization method for the design of antenna pattern applied for mobile broadcasting and the 802.11a WLAN is presented. Based on genetic algorithm (GA), numerical simulation, and unified optimization framework, the optimization methodology is proposed for the antenna design automation. A Z-shaped antenna is optimized with respect to the return loss by our method. Inspired by the scenario of GA for optical proximity correction in our earlier work, we firstly partition the edges of the antenna into segments, and then adjust the movements of each segment to construct the geometry of new antenna. The external simulator is then called to simulate and evaluate the performance of the new antenna. If the simulated results meet the specific constraints, we output the optimized antenna. Otherwise, the evolutionary algorithms will enable us to search solution again. Our preliminary results confirm the robustness and efficiency of the proposed simulation-based optimization method.