Wideband Circularly Polarized mm-Wave Array Antenna Using H-Shaped Low-Axial-Ratio Apertures

An H-shaped all-metal radiating element comprising an active and a coupled slot has been proposed to design wideband high-efficiency circularly polarized antenna arrays. The proper excitation of several modes on the coupled slot enables a wide axial ratio (AR) bandwidth with high circular polarization (CP) purity. To feed an array of such radiating elements, a simple and scalable two-layer corporate network, implemented in groove gap waveguide (GGW) technology, is conceived. Those good frequency properties have been confirmed by the fabrication of a prototype, whose experimental results report a 1-dB AR bandwidth of 22%. In addition, a peak radiation efficiency of 97% with good pattern stability and an impedance bandwidth of 21% with high return loss have been measured. The high CP purity demonstrated by these wideband apertures makes them particularly suitable for Ka-band satellite communications’ antennas.