Annular slots for circularly polarized slotted substrate integrated waveguide array

A new type of circularly polarized slot radiator is presented. Good polarization performances are reached for both left-hand and right hand circular polarization (LHCP, RHCP). The slot configuration consists of an annular slot placed correctly on the upper wall of the waveguide. Several annular contours and positions have been tested and compared. The capability to achieve low Axial Ratio (AR) at low elevation in the plane perpendicular to the waveguide axis can be advantageously used to design 2D waveguide arrays in CP requiring beam scanning in this plane. The annular slot configuration is well adapted to the printed technology of substrate integrated waveguide (SIW).