Circularly Polarized Shared Aperture K-band Transmitarray and Beamforming S-Band Patch Antenna Array

This paper presents a circularly polarized shared aperture antenna. The proposed antenna is a combined S-band patch antenna array and a K-band transmitarray antenna. The high-frequency transmitarray feed and the low-frequency patch antenna array share the same aperture area. The high-frequency transmitarray surface only uses a single substrate layer and is electrically transparent to the low-frequency antenna part. With an impressive frequency-ratio of 5.55 and a radiating area of only 10x10 cm the antenna achieves an impedance bandwidth of more than 1 GHz and 5 GHz, and a peak realized gain of 15.35 dBi and 22.85 dBi, in the S- and K-band respectively. Additionally, the low-frequency antenna mode shows a good beamforming performance with a 120-degree steering range with only a 1.25 dB gain variation.