A radial line slot antenna (RLSA) is a slotted waveguide planar array proposed for DBS subscriber antennas. Predicted conductor loss of RLSA is almost negligible. A single-layered RLSA (SL-RLSA) has the simplest structure. It utilizes non-uniform slots which cancel the tapered aperture illumination associated with a radially outward traveling wave excitation. The efficiency of 70-87% has been realized for SL-RLSAs with the diameters of 0.2m-0.6m. SL-RLSAs were released for commercial use in Japan.
Input power is fed by a coaxial cable at the center and coupled to rotational symmetrical outward traveling wave. A unique feature of RLSA is the use of a radially traveling wave as an excitation of slots. While propagating outward, part of power is radiated from slots. To suppress the grating lobes from the array, the waveguide is filled with the dielectric material. Slots on the top plate consisting of many pairs, each one of which is a unit radiator of circular polarization, are arrayed along a design spiral.
This antenna is a jointly study with Tokyo Institute of Technology.