A low-profile unidirectional cavity-backed log-periodic slot antenna

Abstract

A low-profile unidirectional cavity-backed coplanar waveguide-fed uniplanar log-periodic slot antenna suitable for the ultra-wideband applications (3-18 GHz) is presented. Due to the in- herent balanced structure compared with the unbalanced antennas, such as dipole or loop antenna, the impedance matching and radiation performances of the proposed antenna are quite stable and satisfactory. There is a potential advantage for low profile ultra-wideband unidirectional antennas, and this paper demonstrates a technique for transforming the bidirectional beam into a unidirectional beam by using a special cavity in this ultra-wideband antenna. Meanwhile, the multi-resolution time domain (MRTD) method is applied to analyze this antenna. Experimental results reveal that the cavity has a small affect on the S-parameter of the origin antenna, and remains the perfect reflection property within the desired operation band.