Directive Radiation Excited by Surface Wave with an Equiangular Spiral-shaped Dielectric

Surface waves radiation is popular in object tracking, speed detection. Conventionally, SW radiation is achieved by periodic structures generating -1 harmonic of the propagation constant for wave leakage. The leaky mechanism requires a large size to radiate enough energy and serially gradient structures to realize dispersion manipulation. In this paper, we present a new approach of expected radiation implemented by SW diffraction. The amplitude and phase of the SW diffraction can be controlled by the radius in cylindrical coordinate. An equiangular-spiral-shaped grounded dielectric is analyzed. The simulation and measurement results demonstrate that the manipulations of SW diffraction excited by centre monopole can achieve a broadside circularly polarized radiation.