Novel and simple technique to control the polarization in stub-loaded leaky-wave antennas

Leaky-wave antennas (LWAs) are commonly used to synthesize narrow-beam frequency-scanning radiation patterns by means of a single line-source. By properly controlling the leaky-mode propagation constant, one can flexibly design the pointing direction and the sidelobes distribution. Many studies have been performed in the last years to conceive LWAs that also have polarization flexibility, and particularly to obtain circular polarization. For this purpose, periodic arrays of slots or strips have been added to a host waveguide to induce radiation in the desired polarization. In all these LWA designs, the polarization was controlled by choosing the orientation and dimensions of the periodic perturbations. Normally, complicated orthogonal arrangements of the periodic arrays are needed to obtain circular polarization. In addition, radial waveguides and microstrip lines have also been proposed to obtain vertical and horizontal polarization at the same time, and eventually achieve a circularly polarized main beam. In this contribution, we present a totally original mechanism that allows to control the polarization of the radiated fields in stub- loaded LWAs. The proposed mechanism does not need the introduction of periodic perturbations orthogonally arranged, neither the modification of the host waveguide to obtain a radial shape. As it will be shown, a uniform LWA can be used to excite and control the horizontal and vertical components of the radiated fields.