A compact and high gain metalens antenna based on impedance matching mechanism

A compact wideband metalens antenna which is composed of a log-periodic dipole antenna (LPDA) and metalens is proposed operating over the band of 1.7–2.7 GHz. The metalens is designed by using anisotropic ABA structures (A: impedance matching layer (IML), B: phase gradient metasurface lens (PGMS lens)) to reduce the back-lobe level and achieve high-performance. The PGMS lens is used to achieve a considerable phase shift range, and two IMLs are introduced to eliminate unnecessary reflection caused by the impedance mismatch and further increase phase coverage. Hence, the metalens features a low profile with a thickness of 0.29λ0, where λ0 is the free-space wavelength at 2.2 GHz. The measured results demonstrate that the proposed metalens antenna has a wide impedance bandwidth of 45% (1.7–2.7 GHz) and −3 dB gain bandwidth of 40% (1.8–2.7 GHz), respectively. Moreover, the gain is averagely increased by 9.56 dB in the whole working band, and the maximum gain achieves 16.1 dBi at 2.2 GHz. These characters make the proposed metalens antenna suitable for microwave imaging systems and other applications.