Leaky-wave slit antenna incorporated with a frequency selective surface for terahertz application

Summary form only given. This paper presents the design of a leaky-wave slit antenna incorporated with a frequency selective surface (FSS) in a high-permittivity gallium arsenide (GaAs) substrate for terahertz applications at around 300 GHz. The narrow slit on the top side of the substrate is excited by a delta-gap voltage source at the center and acts as a perfect mirror, and the FSS with an array of circular holes printed on the bottom side of the substrate acts as a partially reflective mirror; thus it forms a Fabry-Perot resonator. The substrate thickness is essentially important to determine the resonance frequency, whereas the periodicity and the diameter of a hole influence the antenna gain and side lobe level of the far-field pattern. More importantly, the geometry of the FSS has to be designed in consideration of the mean effective permittivity of both inside and outside media of the cavity. For device realization, the substrate thickness of 350 μm was chosen from a commercially available GaAs wafer. The FSS was designed with an array of 9 × 9 holes and a periodicity of 330 μm for achieving maximum directivity and good radiation patterns. All results were calculated using the finite-integration timedomain simulator Microwave Studio by CST. The optimized antenna produced a maximum directivity of 18.1 dBi and a radiation efficiency of 61% at 318 GHz. Side lobe levels in two principal planes (E- and H-plane) were approximately -15.1 dB and -15.6 dB, respectively. The size of the antenna was 3.6 mm × 3.6mm × 0.35mm, approximately 3.8λ_o × 3.8λ_o × 0.37λ_o of a free-space wavelength at 318 GHz, which makes the proposed antenna compact, planar, and lightweight as compared with the substrate lens-coupled antenna design.