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

Abstract

SUMMARYThis 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 leakywave 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.

A Method of Generating Radiation Null for Periodic Leaky-Wave Antennas

“…Note that all the mentioned methods were applied to the LWAs with continuous line-source radiation apertures. Also, some of the methods can be utilized to the modulation of periodic LWAs for pattern synthesis [9]- [11]. On the other hand, LWA can be treated as an antenna array of approximated elementary radiators with a short sampling distance [12]- [14], so the existing array techniques [15]- [17] might be useful to synthesize radiation patterns of LWAs.…”

“…On the other hand, LWA can be treated as an antenna array of approximated elementary radiators with a short sampling distance [12]- [14], so the existing array techniques [15]- [17] might be useful to synthesize radiation patterns of LWAs. As originally explained in [2], [11]- [14], the condition is that the sampled elementary radiators that form the discretized LWA aperture are not independent, but they have coupling effect from the leaky mode. The LWA can be tapered or modulated, but in a slight or smooth manner to avoid unwanted radiation due to strong discontinuities (reflected and diffracted waves).…”

Electromagnetic Modeling of Sub-Wavelength Periodic Structures from Guided-Wave Devices to Metasurface Scatterers

“…In contrast, the two modes are completely disconnected in the lossless case. Also, the possible ± sign while solving for γ in (5.27) is selected so that both modes present a positive group velocity, which for a forward propagating wave requires a positive α for attenuation in space, which is in agreement with the sign choices and physical interpretation of the wavenumber as presented in [130].…”