| Broadband Circularly Polarized Antenna with Stable Flat-Top Radiation Based on Metasurface |
Seungmo Hong1 
, Danh Manh Nguyen2
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1School of Electronic Engineering, Soongsil University, Seoul, Korea
2Department of Telecommunication Engineering, Soongsil University, Seoul, Korea |
Correspondence:
Danh Manh Nguyen,Email: nguyendanhmanh1998@gmail.com
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Received: 31 July 2025 • Revised: 3 November 2025 • Accepted: 3 December 2025 |
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| Abstract |
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This paper presents a compact broadband circularly polarized antenna based on a metasurface. The antenna is designed to minimize transmission losses in microwave power transfer (MPT) systems while ensuring a stable flat-top radiation pattern for efficient energy transmission. The proposed structure is composed of aperture-coupled feeding and a metasurface in which four-unit cells are sequentially eliminated to enhance the antenna’s circular polarization (CP) characteristic s. The antenna is fabricated and experimentally validated in this work, with measurements indicating strong agreement with the simulation results. Moreover, the antenna demonstrates excellent impedance matching across a wide bandwidth of 22.65% (4.46–5.85 GHz) and broadband CP characteristics with an axial ratio (AR) less than 3 dB over the 4.66–5.88 GHz range. The proposed antenna also maintains a stable flat-top (1-dB) radiation pattern throughout its operational frequency range. At 4.8 GHz, the flat-top beamwidths for the E-plane and H-plane are 58% and 60%, respectively, with a realized gain of 7.5 dBi. At 5.8 GHz, the flat-top beamwidths are higher than 56% in both planes, with a realized gain of 8.2 dBi. The proposed antenna offers superior performance in terms of compactness, a broadband flat-top beam, and broadband CP compared to those developed in previous studies. |
| Key words:
Broadband Antenna, Circular Polarization (CP), Compactness, Flat-Top Radiation Pattern (FTRP), Microwave Power Transfer (MPT) |
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