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Spoof surface plasmon polaritons (SSPPs) are highly confined surface electromagnetic waves, which can be supported by subwavelength periodic metal structure. According to the theory of sinusoidally modulated reactance surface (SMRS), SSPPs could be transformed into directional leaky-wave radiation through wavenumber modulation. In this paper, we propose a method to suppress the sidelobe level of the plasmonic leaky-wave antenna by designing a non-uniform sinusoidally modulated plasmonic waveguide composed of double edge corrugated metallic strip. A low sidelobe plasmonic leaky-wave antenna has been designed by controlling the amplitude of SSPPs to be a taper distribution on the aperture of plasmonic waveguide. Furthermore, an unsymmetrical SSPPs waveguide is designed by staggering corrugated grooves on two sides with μ/4 offset to increase the radiation efficiency at broadside. Both numerical simulations and experimental results have good agreements, which show that this method is effective to reduce the sidelobe of leaky-wave radiation by using non-uniform sinusoidally modulation of the plasmonic waveguide.

The plasmonic waveguide made of uniform corrugated metallic strip can support and guide spoof surface plasmon polaritons (SSPPs) with high confinements. Here, we propose periodically-modulated plasmonic waveguide composed of non-uniform corrugated metallic strip to convert SSPPs to radiating waves, in which the main beam of radiations can steer continuously as the frequency changes. To increase the radiation efficiency of the periodically-modulated plasmonic waveguide at the broadside, an asymmetrical plasmonic waveguide is further presented to reduce the reflections and realize continuous leaky-wave scanning. Both numerical simulations and experimental results show that the radiation efficiency can be improved greatly and the main beam of leaky-wave radiations can steer from the backward quadrant to the forward quadrant, passing through the broadside direction, which generally is difficult to be realized by the common leaky-wave antennas.