Co-Aperture Dual-Circular-Polarized Patch Antenna for Simultaneous Transmit and Receive

A co-aperture dual-circularly polarized antenna for simultaneous transmit (Tx) and receive (Rx) sensing systems is proposed in this letter. The antenna consists of a radiating patch, a dielectric substrate, and a ground plane. Embedding a rectangular slot in the center of the patch implements left-handed circular polarization for Tx and right-handed circular polarization for Rx. A pair of U-shaped slots (USS) with a 90° phase shift is placed into the ground plane for decoupling. When the USS works, the mutual coupling in the
x
- and
y
-direction cancels each other at the Rx port. As verification, a prototype with the size of
$0.43{\lambda }_0 \times 0.43{\lambda }_0 \times 0.01{\lambda }_0$
is fabricated and measured. The operating bandwidth, in which
$| {{S}_{11}} |$
and axial ratio are respectively less than –10 and 3 dB, is 4.32–4.42 GHz. Within this band, the measured peak realized gain is 5.4 dBi, and the isolation is better than 23 dB with a maximum of 34 dB. In comparison with other works, the proposed antenna is competitive in terms of antenna size, aperture efficiency, and total efficiency.