Transmission-Line Model of Nonuniform Leaky-Wave Antennas

Nonuniform leaky-wave antennas (LWAs) are analyzed and synthesized using a lossy transmission line model. The analysis is based on a general waveguide circuit theory. Compared to the classical approach, the model yields a higher accuracy in the computation of both aperture field distribution and radiation patterns. The proposed analysis is also able to provide scattering parameters of the whole structure in a fraction of a second, which is valuable for antenna optimization. Based on the analysis, a general method for far-field pattern synthesis utilizing global optimization is presented. As an application demonstration, the half-mode substrate-integrated waveguide (HMSIW), or half-width microstrip line, has been selected as basis structure for the LWA designs. Two antennas have been optimized targeting different specifications, i.e., a low-sidelobe level and a wide null in the radiation pattern. Experimental results are provided for these selected examples of nonuniform LWAs, which ultimately validate the proposed technique as an improvement over the classical approach.