Collimating cylindrical Surface Leaky Waves for Highly Improved Radiation Characteristics of Holograms

Abstract

High resolution microwave leaky wave holograms excited by center-fed cylindrical surface wave launcher show a null at object wave direction which is an undesired effect for electromagnetic beamforming. Also, planar leaky wave metasurfaces generating a tilted beam extremely suffer from the destructive effect of non-forward surface leaky waves at frequencies other than the design frequency and they are almost operable at a single frequency. Here we propose a 2-D modified hologram configuration using parabolic surface reflector to collimate the non-forward leaky modes into the forward leaky modes. The modified hologram presents null-free radiation pattern and highly improved operating frequency bandwidth. The consequent frequency bandwidth provides the scannabality property by frequency variation. The forward mode-dominant surface wave excitation of hologram lets the metasurface to generate the object beam more precisely; therefore, high directivity all over the operating bandwidth is obtained. The parabolic reflector lets the radiative surface of the metasurface to get shrunken in less than half of the conventional holograms. The concept is verified by fabrication and experimentally tested confirming the beam maintenance over a reasonable frequency range and scannability property.