Polarization-Converting Metasurface Inspired Dual-Band Dual-Circularly Polarized Monopole Antennas for Off-Body Communications

• Published in: IEEE antennas and wireless propagation letters Vol. 22; no. 1; pp. 194 - 198
• Main Authors: Sahu, Nibash Kumar, Mishra, Sanjeev Kumar
• Format: Journal Article
• Language: English
• Published: New York IEEE 01-01-2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Antenna radiation patterns; Antennas; Circular polarization; Circular polarization (CP); Conversion; Dual band; Frequencies; Geometry; High gain; Metasurfaces; Monopole antennas; Monopoles; off-body communication; Phase change materials; polarization-converting metasurface (PCMS); Reflector antennas
• ISSN: 1536-1225; 1548-5757
• DOI: 10.1109/LAWP.2022.3206913

This letter investigates a novel technique to achieve circular polarizations (CPs) at 2.45 GHz ISM and 3.5 GHz WiMAX bands. The behavior is achieved by incidenting an <inline-formula><tex-math notation="LaTeX">x</tex-math></inline-formula>-polarized wave from a monopole antenna (MA) on a polarization-converting metasurface (PCMS). The PCMS operates in TM<inline-formula><tex-math notation="LaTeX">_{10}</tex-math></inline-formula> and TM<inline-formula><tex-math notation="LaTeX">_{20}</tex-math></inline-formula> modes that generate dual frequency bands and reflect a 90° phase-shifted y-polarized wave that, when combined with the 0° phase containing <inline-formula><tex-math notation="LaTeX">x</tex-math></inline-formula>-polarized wave, generates CP. To attain four separate combinations of phase-shift in terms of +90° and −90° in dual bands, four distinct 2×2 PCMSs are designed, which are designated as MS<inline-formula><tex-math notation="LaTeX">_{1}</tex-math></inline-formula>, MS<inline-formula><tex-math notation="LaTeX">_{2}</tex-math></inline-formula>, MS<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula>, and MS<inline-formula><tex-math notation="LaTeX">_{4}</tex-math></inline-formula>. The MS<inline-formula><tex-math notation="LaTeX">_{1}</tex-math></inline-formula>-based MA (A<inline-formula><tex-math notation="LaTeX">_{1}</tex-math></inline-formula>) produces left-hand CP (LHCP), whereas the MS<inline-formula><tex-math notation="LaTeX">_{2}</tex-math></inline-formula>-based MA (A<inline-formula><tex-math notation="LaTeX">_{2}</tex-math></inline-formula>) produces right-hand CP (RHCP) in both frequency bands. On the other hand, the MS<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula>-based MA (A<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula>) produces RHCP in the lower band (LB) and LHCP in the higher band (HB), whereas the MS<inline-formula><tex-math notation="LaTeX">_{4}</tex-math></inline-formula>-based MA (A<inline-formula><tex-math notation="LaTeX">_{4}</tex-math></inline-formula>) produces LHCP in the LB and RHCP in the HB. A<inline-formula><tex-math notation="LaTeX">_{3}</tex-math></inline-formula> is fabricated and measured, and the results are very close to the simulations. Each antenna has a wide impedance bandwidth, a high gain, and high efficiency with a low specific absorption rate (SAR) in the desired bands, which justifies their suitability for off-body communication.