Pencil-Beam Single-point-fed Dirac Leaky-Wave Antenna on a   Transmission-Line Grid
  Leaky-wave antennas (LWAs) are widely used as single-point-fed linear antenna arrays. The extension of LWAs to 2D implies that they can be used as single-point-fed 2D antenna arrays without requiring a complex feeding network. However, generating a pencil beam from 2D LWAs is not straightforward and due care has to be taken for the design of the LWA. On the other hand, transmission-line (TL) grids have demonstrated interesting behaviors, such as an effective negative refractive index and growing of evanescent waves. In this paper, a singlepoint-fed TL-grid 2D Dirac leaky-wave antenna (DLWA) design is proposed that generates a pencil beam at both broadside and slightly tilted angles. The TL-grid unit cell is analytically treated in light of its scattering and impedance matrices. The optimized TL-grid unit cell is shown to exhibit a closed bandgap in the dispersion relation which is also linearly varying with frequency (hence it is a DLWA). The proposed 2D DLWA design is fabricated and the experimental results are presented. 
Ayman H. Dorrah and George V. Eleftheriades
physics.class-ph