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.