| Summary: | A novel beam steerable antenna employing tunable high impedance surface with liquid crystal is proposed. This antenna utilizes three microstrip patches as the radiators and a tunable high impedance surface based on liquid crystal as the ground plane. In this design, liquid crystal is deliberately disposed under the two parasitic microstrip patches to reduce the effect of relatively large dielectric loss and to improve the gain and radiation efficiency of the antenna. More importantly, this work explores a tunable high impedance surface based on liquid crystal, which has advantages of simple structure and biasing scheme as compared with other tunable high impedance surfaces based on solid-state devices. It is shown that by tuning the permittivity of liquid crystal, the high impedance surface becomes to support the propagation of TE surface waves to strengthen the mutual coupling between main and parasitic microstrip patches. Consequently, the main lobe can be steered to the desired direction and the scanning range of the antenna is enlarged. To prove this novel concept, a Ka-band prototype is fabricated and tested. Measured results show that the antenna not only has acceptable gain, but also keeps a satisfactory scanning range. In addition, this antenna consumes negligible DC power and thus is a strong antenna competitor for 5G access point applications.
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