Abstract: A multi-band, shared-aperture, circularly polarized phased array antenna relating to the field of antenna technology is disclosed. Specifically, two multi-band, shared-aperture, circularly polarized phased array antenna designs are disclosed. By integrating multiple circularly polarized endfire antennas with different operation bands into one aperture, a shared-aperture antenna array is achieved. The bandwidth and crossband port isolation of this antenna are enhanced, and the antenna also has the properties of miniaturization, feasibility, and ease of connection with circuits.