In this paper, we report the design, fabrication, and experimental measurement of a compact co-designed circularly polarized (CP) filtering antenna with a wide operational bandwidth. In the filtering antenna module, the radiator serves simultaneously as the last resonator of the filter which was realized by coupled stripline open-loop resonators. A proof-of-concept design is presented with both its S11 <-14 dB and axial ratio < 3 dB bandwidths covering 12.5%, ranging from 3.75 to 4.25 GHz. A prototype was fabricated and characterized, showing strong agreement between simulated and measured results. The gain response exhibits a profile similar to the transmission of a bandpass filter. The integrated filtering and radiating modules with a compact form factor and improved performance metric are expected to find potential applications in a variety of wireless communication systems.