Ka-band tunable reflectarray unit cell using BST technology

A Ka-band tunable reflectarray unit cell is presented in this paper using Barium Strontium Titanate (BST) technology. A rectangular patch is capacitively loaded with a narrow gap in the middle and a layer of BST thin film is deposited underneath the gap. The BST layer is patterned so that it is limited only under the gap to minimize the total loss. Varying the permittivity of the BST material changes the effective capacitance of the gap. Therefore, the reflection phase of the reflectarray unit cell can be continuously controlled. Simulation results exhibit 114° phase shift at 32 GHz. Due to the monolithic integration of the tuning mechanism with the unit cell, this configuration can be realized at millimeter-wave frequencies without suffering from packaging and bonding problems.