A Shared-Aperture Linearly/Circularly-Polarized Filtering Antenna Array with Low Profile

A Dual-band (2.6/3.5 GHz) shared-aperture filtering antenna array with a 0.067λ0 profile is proposed. The antenna array working at the high-band has right-handed circular polarization (RHCP), while the array working at the low-band exhibits linear polarization (LP). For the high-band subarray, parasitic patches are introduced to obtain a wide effective operation band, and substrate integrated waveguide (SIW) cavities are utilized to excite a radiation null, leading to a sharp roll-off at the lower band-edge. For the low-band LP antenna subarray, two U-shaped metal strips are used to improve the impendence bandwidth and produce a radiation null, resulting in a sharp roll-off at the upper band-edge. As a result, the two subarrays can be placed closely within the same aperture, and a high isolation of over 30 dB between them can be achieved. The antenna is prototyped and tested, the high subarray has an effective bandwidth of 3.27-3.66GHz with |S11|≤-10dB, AR≤3dB, and a stable gain of 9.5dBi, and the low subarray has an -10dB impedance bandwidth of 2.49-2.75GHz with gain of 10.5 dBi.