A Tunable Metagratings Leaky-Wave Antenna Based on Liquid Crystal

An electrically tunable wide-beam-scanning metagratings leaky-wave antenna (MGs LWA) based on liquid crystal (LC) is proposed. Two-dimensional (2D) periodic slotted MGs with capacitive and inductive behaviors are etched on the bottom layer of the substrate and backed by a ground plane with an LWA framework. Two different slotted MG elements are adopted to suppress the open-stopband effects. A theoretical analysis is conducted to provide a conceptual framework for the equivalent electromagnetic fields generated by slotted MGs. Using LC, tunable beam scanning is achieved at a fixed frequency. The LC is placed between the inverted MGs LWA radiating metal and the ground plane to control the LC molecules' orientation angle by applying a DC voltage across them, thereby adjusting the LC permittivity. Using the results obtained, the proposed antenna can be tuned up to 40° at a fixed frequency by applying a biased DC voltage ranging from 0 V to 10 V. The actual operating bandwidth is 40% for continuous beam scanning of 71°, with a scanned sensitivity of 8.35°/GHz at the zero voltage (V = 0 V), and beam scanning of 61°, with a scanned sensitivity of 7.17°/GHz at the saturation voltage (V = 10 V). The proposed MGs LWA has a realized gain of up to 13.84 dBi. Finally, the proposed antenna has excellent performance due to its potential to achieve wide tunable beam scanning with a narrow beamwidth compared to traditional LWAs' limitation of radiation angle, depending on the excitation frequency, which makes the proposed antenna suitable in terms of range and sensing calibration for operation at a specific frequency in sensing communication and radar applications.