A　circularly　polarized　phased　array　is　proposed　and　analyzed　at　28　and　38　GHz　for　5G　communications.　Radiations　of　the　antenna　element　in　the　two　bands　are　realized　by　four　annular　slots　and　four　rectangular　slots　etched　on　a　substrate　integrated　waveguide　(SIW)　cavity.　Broadside　radiation　patterns　in　two　frequency　bands　are　investigated　by　characteristic　mode　analysis　(CMA),　and　the　circular　polarization　is　realized　by　exciting　a　pair　of　orthogonal　modes　with　a　phase　difference　of　90°　and　an　identical　amplitude.　The　simulation　results　show　that　the　-10dB　impedance　bandwidths　of　the　antenna　element　are　26.1-29.4　and　36.2-39.1　GHz.　Then　an　array　configuration　of　2×2　elements　is　designed　to　realize　the　beam　scanning　capability　under　excitations　with　different　phase　shifts.　In　the　simulation,　the　broadside　realized　gains　of　the　right-handed　circular　polarization　are　10.4　and　12.5　dBi　in　the　low　and　high　bands,　respectively.　The　maximum　scanning　angles　of　the　2×2　phased　array　are　±30°　and　±25°　in　the　low　and　high　bands,　respectively.　©　2022　IEEE.