  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.
