A Shared-Aperture Antenna With High-Aperture Reuse Efficiency and High Isolation Based on the Quasi-Yagi Structure

This article presents a shared-aperture antenna that covers the UHF-, S-, and C-bands. It comprises a folded dipole antenna (FDA) that operates in the UHF-band and a dual-polarized planar bowtie antenna (PBA) covering the S-/C-band. The lower band (LB) and higher band (HB) antennas serve as the reflector and director for each other, respectively, which results in an aperture reuse efficiency of 100%. Both antennas are very compact in size and exhibit unidirectional radiation patterns. The shadowing effects of the HB antenna are rigorously analyzed through the quasi-Yagi scenario. A general guideline for reducing the shadowing effects is strictly deduced and verified. To improve the isolation between the LB and HB antennas, the two antennas are incorporated with low-pass and band-stop filtering responses, respectively. The proposed shared-aperture antenna has an impedance bandwidth of 0.77–1.06 and 2.2–6.6 GHz, with an isolation greater than 30 dB. Additionally, the two polarization ports of the HB antenna have an isolation of greater than 20 dB in the S-/C-bands. The presented design is compact, broadband, and efficient, which is potentially useful for airborne platform.