This communication presents an effective approach to design the dual-band dual-mode (DBDM) patch antenna with flexible frequency ratio, wide achievable range, and compact configuration. Initially, the TM00 and TM10 modes of such an antenna are theoretically studied based on the transmission-line model. It is revealed that the lower resonant frequency of the TM00 mode could be effectively reallocated by properly introducing the inductance at its center. Meanwhile, the upper resonant frequency of TM10 mode remains unaffected during this process. This theoretical analysis provides a physical insight into its working mechanism. Then, a set of shorting pins is symmetrically loaded in the center of the patch radiator to make use of their equivalent inductance for flexible control of its operating frequency. After parametric analysis is extensively executed, a unified design procedure is summarized. With these arrangements, a wide frequency ratio of two operating bands could be flexibly realized in a range from 1.38 to 3.36. Finally, two DBDM antennas with the same patch contour but distinct frequency ratio, i.e., 1.38 and 3.36, are designed, fabricated, and tested. The simulated and measured results are found in good agreement with each other, thereby certifying the validity of the proposed method. All these results indicate that the proposed design approach with flexible frequency ratio, wide achievable range, concise procedure, and compact configuration could be widely applied to the modern communication systems.