Dual-circularly polarized (CP) antenna planar cavity- backed antenna is proposed for broadband applications. The antenna is realized by exploiting a stacked structure of two-layer dielectric substrates, where the top layer comprises substrate integrated waveguide (SIW) planar cavity and radiating square shaped patch. To realize dual-CP, the patch is excited by pins, which are symmetrically placed at an offset to the diagonal axis of the patch. Furthermore, these pins are excited individually by two 50 ñ printed microstrip line feeds at the back side of the second layer of the substrate. Thus, right-handed circular polarization/left-handed circular polarization (RHCP/LHCP) can be realized by a one feeding line at a time. Moreover, this feeding topology is found useful for bandwidth enhancement. These pins introduce strong loading effect in the cavity and generate additional resonance in the vicinity of the patch resonant that help to achieve a broadband frequency response. The simulated results show that an antenna is operating for an impedance bandwidth of nearly 8.59 to 11.43 GHz and an axial-ratio bandwidth of early 500 MHz under the mandatory criterion of less than 3-dB for CP. © 2017 IEEE.