Thermally Actuated Vanadium Dioxide Millimeter Wave Reflectarray

This paper presents the development of a reconfigurable vanadium dioxide $(\mathbf{VO}_2)$ based reflectarray antenna using a novel 1-bit split patch element. The thermally actuated unit cell, composed of a quarter wavelength $(0.25\lambda_0)$ copper patch and a VO2 thin film switch is able to achieve $\boldsymbol{180}^{\mathrm{o}}$ of phase at 35 GHz with a maximum loss of 0.35 dB. Such a design exploits the reversible metal to insulator transition properties of $\mathbf{VO}_{2}$ at $68^{\circ}\mathrm{C}$. The simplicity of such an element provides a low cost practical reconfiguration strategy that can be extended to large apertures. A full-wave $\boldsymbol{40\times 40}(10\lambda_{0}\times 10\lambda_{0})$ simulation of the switchable device demonstrated a maximum gain of 21.1 dB at $\mathrm{0}^{\circ}$ and 1D beam scanning performance covering $-60^{\mathbf{o}}$ to $+60^{\mathbf{o}}$ with a 4.5 dB reduction in peak gain over the full scanning range.