Eight different nonlinear systems are considered in order to overcome the main drawback of existing vibration generator, the narrow bandwidth problem. Based on the static and dynamic analysis of these systems, the typical nonlinear softening and hardening Duffing oscillator systems have been selected for further consideration. The limitations of the selected systems are presented here. The softening system becomes unstable when the forcing amplitude exceeds the critical value, and the response amplitudes of the hardening system will be reduced by the extra stiffness introduced by the nonlinear term. Therefore, a mechanical system, which exhibits the dynamic characteristics of the softening system at the low force level while showing as the hardening with the increasing forcing, is proposed. With the assistance of the numerical method, it can be observed that the frequency response curves (FRCs) of the system will lean to left hand side of the linear resonance frequency when the forcing amplitude is comparatively low, and lean to the right when the input force can burst the energy barrier. More dynamic behaviors are discussed. According to the analysis, the proposed nonlinear system can be the solution to the narrow bandwidth problem.© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.