A Single Substrate Metasurface Dipole With Electrically Small Feeding Structure

Low-profile metasurface antennas are proposed for cellular base station applications. The dual-slant crossed-dipole antennas with four resonances employ both transverse magnetic (TM) and transverse electric (TE) surface wave modes. The metasurface dipole arms are capacitively coupled by an electrically small crossed-feed in a low-cost single substrate. The metasurface layer consists of <tex-math notation="LaTeX">n × n </tex-math> element arrays. The proposed low-profile ( <tex-math notation="LaTeX">0.14λ </tex-math> ) antennas can achieve a 10-dB impedance bandwidth of 57%, 58%, and 84% for metasurface dipole arms comprising <tex-math notation="LaTeX">2× 2 </tex-math> , <tex-math notation="LaTeX">3× 3 </tex-math> , and <tex-math notation="LaTeX">4× 4 </tex-math> elements, respectively. For cellular 65° sector base station applications where 14 dB is required, a bandwidth of 51%, 52%, and 63% for <tex-math notation="LaTeX">2× 2 </tex-math> , <tex-math notation="LaTeX">3× 3 </tex-math> , and <tex-math notation="LaTeX">4× 4 </tex-math> elements, respectively, is realized. For a single dipole with a reflector, the average boresight gain is 9 dBi, 3-dB beamwidth is <tex-math notation="LaTeX">62∘~± ~7∘ </tex-math> , front-to-back ratio is better than 25 dB, and isolation is better than 35 dB over the frequency range of 1.7–2.7 GHz. For user equipment (UE) applications, extra low-profile ( <tex-math notation="LaTeX">0.11λ </tex-math> ) antennas are also presented.