Fundamental properties of broadside radiation from uniform leaky-wave antennas

In this work, radiation at broadside is studied for a general class of one- and two-dimensional uniform leaky-wave antennas. The analysis, based on a simple transverse equivalent network model of the antenna, reveals that a fundamental condition for optimum antenna operation at broadside is the equality between the phase and attenuation constants of the leaky mode responsible for radiation. This corresponds to having the maximum level of radiation at broadside and the beam being on the verge of splitting into two distinct peaks off broadside. Simple design formulas based on the optimized conditions are provided for both lossless and lossy structures. In addition, the antenna bandwidth for operation at broadside is studied and a useful approximate expression for the fractional bandwidth is given in terms of the physical parameters of the antenna.