Contribution to the improvement on flat reflectors
José Ángel García, Ramón Gonzalo, Julio Gutiérrez-Ríos, Antonio Tazón and Juan Vassal'lo
Conventional leaky-wave (LW) antennas operate in a higher order space harmonic of their fundamental mode. Frequency scanning from backfire to endfire direction is not possible without any blind spots especially at broadside. In literature it is stated that LW antennas which operate in their fundamental mode should be able to radiate in broadside direction without a blind spot. In order to attain this goal a feeding network should exhibit left-handed and right-handed fast guided wave propagation properties.
A first approach is based on an artificial wire medium with printed patch elements forming a metallo-dielectric surface of the mushroom-type. Modifications of the gap width between the patches show that it is possible to operate in the backfire region below the wire medium's cutoff frequency. Measured data on a demonstrator antenna indicate the possibility of a continuous frequency scan from backfire to endfire direction.
In a second example a similar approach is used for a cylindrical leaky-wave antenna by wrapping the metallo-dielectric medium around a metallic cylinder. The patch elements of the mushroom surface are connected circumferentially. This modification creates a cylindrical surface with circumferential slots that contribute to conical radiation pattern. Numerical results indicate forward scanning over a large bandwidth with high radiation efficiency and directivity.