We discuss all possible responses of a linearly polarized light passing through two linear retarders. Based on this theory, a complete polarization state generator (PSG) composed of a fixed polarizer and two rotating retarders is proposed. The restriction on the phase retardances of the two retarders is given, and the procedures to determine the orientations of the two retarders to generate any pre-specified elliptical polarization state are presented. Compared with the traditional PSG, our design has the advantage that the working wavelength can be selected in a rather broad range. At the same time, our system only requires two normal linear retarders, and is thus cheaper than the PSG composed of achromatic or variable retarders. In addition, by selecting the retardance values of the two retarders, our complete PSG can also be designed to show a good broadband property, such as generating a specific polarization for an extended range of wavelengths under white light illumination. Finally, the comprehensive analysis of a linearly polarized light passing through two linear retarders presented in our paper is also inspiring for the design of other related systems.