A Broadband Filtering Circularly Polarized Folded Transmitarray Antenna Based on Metasurface

This letter presents a broadband filtering circularly polarized (CP) folded transmitarray antenna (FTA) with a linearly polarized (LP) feed antenna based on metasurface (MS). The whole antenna mainly consists of two MSs located on the top and bottom layers and an LP feed antenna. LP to CP wave (LP-CP) conversion and phase compensation are achieved across the entire X-band with the designed top MS. The top bandpass MS is also used as a spatial filter, utilizing its out-of-band suppression characteristics and high passband edge selectivity. A fabricated prototype was measured, and the results reveal that its maximum gain is 27.8 dBi at 10.2 GHz with an aperture efficiency of 40%. It also achieves a 3 dB gain bandwidth of 24.5% and a 3 dB axial-ratio bandwidth of 41.1%, which is in good agreement with the simulation results as well. The proposed broadband CP FTA achieves a bandpass filtering response while also retaining the advantages of low profile, high gain, and low cost, which illustrates great application potential in future wireless communication systems.