Beam Scanning Leaky-Wave Slot Antenna Using Balanced CRLH Waveguide Operating Above the Cutoff Frequency

In this paper, a composite right-left-handed (CRLH) rectangular waveguide satisfying a balanced condition above the cutoff frequency and a beam scanning leaky-wave slot antenna are presented. The proposed metamaterial waveguide consists of one shorted stub and two H-plane irises, which produce a negative permittivity and negative permeability, respectively. To design a balanced CRLH transmission line, the H -plane irises are materialized by twisted shapes that present a minimized coupling with the shorted stub. The independent controls of the LH and RH regions above the cutoff frequency make it relatively easy to obtain a balanced condition due to the minimized coupling effects. Additionally, using the CRLH waveguide, a beam scanning leaky-wave antenna (LWA) is designed. The LWA achieves good leakage radiation and high gain performance through insertion of the slot, which is set as close as possible to the operating frequency band. The design results show that the LWA supports the backward to forward beam scanning property, including a broadside radiation pattern by changing the frequencies without a band gap. The antenna consisting of 20 unit-cells has a beam steering angle from -31° or +52° and a high gains performance of more than 11.5 dBi in a frequency band from 9.5 GHz to 12.4 GHz.