Circularly polarized antenna and communication system

A communication system comprising a circularly polarized antenna, wherein the circularly polarized antenna comprises an antenna unit and a feeding unit, and the antenna unit and the feeding unit are stacked up and down;

• the antenna unit is arranged on a first substrate, and the antenna unit comprises:
• a first antenna subunit comprising a metal patch in a cross shape, wherein the first antenna subunit is arranged on a top layer of the first substrate;
• a parasitic element comprising four metal strips forming a square with four unconnected sides, wherein the parasitic element is arranged in a middle layer of the first substrate;
• a second antenna subunit, wherein the second antenna subunit comprises a square metal patch, and the second antenna subunit is arranged on a bottom layer of the first substrate;
• the feeding unit is arranged on a second substrate, and the feeding unit comprises:
• a coupling slot group, arranged on a top layer of the second substrate;
• a matching microstrip line group, arranged on a middle layer of the second substrate;
• a feeding line group arranged on a bottom layer of the second substrate;
• a branch line coupler arranged on the bottom layer of the second substrate, wherein the matching microstrip line group is electrically connected between the feeding line group and the branch line coupler through a hole group.