This communication presents a novel design of a compact microstrip antenna practical for both the global positioning system (GPS) and digital communication system (DCS). The proposed antenna consists of two parts: a fundamental mode truncated square patch antenna and a higher-order mode annular ring patch antenna. The truncated square patch operated in right-hand circular polarization at 1575 MHz with 8-MHz CP bandwidth, making the design suitable for the GPS. Further, four slots were embedded into a ground plane to meander the current path of the annular ring patch at the TM21 mode, which considerably lowered the resonant frequency and effectively increased the impedance bandwidth. These features reduce the antenna size and make the design appropriate for DCS. Both radiators are placed in a common space but operate independently. The experimental results show that this design is ideally suited for GPS/DCS dual-band mobile communications.