Efficient full-wave analysis method of leaky-wave modes in periodically loaded dielectric waveguides with application to backward-to-forward frequency-scannable antennas and metamaterials

This work presents a novel and efficient full-wave method specifically conceived for the modal analysis of periodic planar metallizations printed on the open side of a dielectric rectangular waveguide. This particular type of structures can be used to conceive interesting backward-to-forward frequency-scanning periodic leaky-wave antennas, including leaky-wave antennas based on the composite right-left-handed transmission line concept (metamaterial). For the analysis, the spectral-domain Green's functions are obtained by expanding the electromagnetic fields as a double summation of Floquet and parallel-plate modes. An original and simple coupled equivalent circuit is used to deal with the multilayered stratification arrangement and the top radiation boundary. The method of moments (MoM) is applied to solve the corresponding EFIE/MFIE, and an original iterative technique is used to search for the complex leaky-wave mode zeros of the determinant of the MoM matrix. All the expressions are in closed form, while keeping its full-wave nature. The convergence and the accuracy of the method are both studied. Once the backward leaky-waves are found, some interesting phenomena are examined, such as backward-to-forward beam scanning, appearance of bandgaps, mode coupling, multi-space-harmonic radiation, and antenna aperture illumination control. By studying a practical antenna and by comparing with previously published methods, it is shown the importance of a full-wave analysis tool that can take into account all the aforementioned effects. Copyright © 2006 John Wiley & Sons, Ltd.