US Patent 7439913 Microstrip reflectarray antenna

A microstrip reflectarray antenna with a low cross polarization level is disclosed. The microstrip reflectarray antenna of the present invention comprises: a ground plate; a reflecting plate with an upper surface, and a plurality of microstrip antenna units locating on the upper surface; each of the microstrip antenna units consisting of an inner ring and an outer ring; a plurality of supporting units for supporting the reflecting plate above the ground plate; and a signal transmitting unit locating above the reflecting plate for transmitting and receiving the high frequency signal. Besides, the size of the outer ring corresponds to its location on the upper surface of the reflecting plate, and there is a predetermined ratio between the diameter of the outer ring and the diameter of the inner ring, and both of the outer ring and the inner ring respectively have at least one slot.