A Ka-band low-profile beam steering slot antenna using a CRLH substrate integrated waveguide

A low-profile beam steering slot antenna using a composite right/left-handed (CRLH) waveguide implemented in a substrate integrated waveguide (SIW) configuration is designed aiming for millimeter-wave radar applications. The antenna consists of a cut-off waveguide and a periodic array of capacitive stubs yielding negative permittivity and negative permeability, respectively. The antenna operates with the balanced CRLH condition and has a wide-range backward to forward beam steering operation including the broadside radiation by frequency scanning. In order to obtain a wide range beam steering in a limited bandwidth, an additional inductive stub is introduced in the unit cell. The antenna is designed and implemented at 35 GHz band in an SIW substrate with the total thickness of 0.3 mm. Controllability of the bandwidth control by the inductive stub is numerically confirmed. Radiation characteristics of the designed antenna are also calculated by full-wave simulation, and numerical simulations reveal a wide range beam steering performance within plusmn30 deg with a frequency sweep from 34.8 GHz to 35.22 GHz.