Low-RCS UWB Planar Monopole Array Antenna Based on the Optimized Design of the Conductor Layers

Abstract

Using an optimized design of combining traditional copper (Cu) film and novel phase transition film vanadium dioxide (VO2), this communication proposes an ultrawideband (UWB) planar monopole array antenna with excellent stealth performance. The VO2 film exhibits two controllable phases: one with low conductivity of less than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{3}$ </tex-math></inline-formula> S/m and the other with high conductivity of more than <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10^{6}$ </tex-math></inline-formula> S/m. Since VO2 has lower conductivity than Cu, antenna designs using this material will have lower radiating efficiency as a tradeoff for reducing the radar cross Section (RCS). To optimize this tradeoff, careful antenna shape design, and an innovative combination of using VO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{2}+$ </tex-math></inline-formula> Cu films, the RCS can be reduced in a UWB without significantly decreasing the gain of the array antenna. In this work, Cu is applied in the regions supporting high current density, while phase transition VO2 film is used in areas supporting lower current density. Both the shape and size of the VO2 film are optimized. Compared with the all-Cu film counterpart, the realized gain of the VO <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{2}+$ </tex-math></inline-formula> Cu hybrid film array antenna is decreased only by an average of 0.4 dBi, maintaining the same radiation pattern in the working band of 6–9 GHz, while the monostatic RCS is reduced by about 9 dB on average across the UWB of 4–11 GHz.