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 two dimensions (2-D) implies that they can be used as single-point-fed 2-D antenna arrays without requiring a complex feeding network. However, generating a pencil beam from 2-D 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 letter, a single-point-fed TL-grid 2-D 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 that is also linearly varying with frequency (hence, it is a DLWA). The proposed 2-D DLWA design is fabricated, and the experimental results are presented.