Antenna Arrays Antenna measurements antenna radiation patterns array antenna Arrays Bandwidth broadband antennas broadband metamaterial-based array antenna compact metamaterial based array antenna composite material composite materials DL-EBG dual-layer EBG dual-layer electromagnetic bandgap electromagnetic wave polarisation gain 8.5 dB in-phase reflector plane low-profile Metamaterial metamaterial antennas metamaterial-based thin monopole-like elements Metamaterials monopole antenna arrays offset mushroom-like Sivenpiper EBG arrays omnidirectional antennas omnidirectional radiation Ondes ElectroMagnétiques Matériaux et Systèmes Periodic structures photonic band gap vertical polarization