Broadband Colinearly Polarized Antenna With a Shared Radiator for STAR Applications

This letter proposes a broadband co-linearly polarized antenna with a shared radiator for simultaneous transmit and receive (STAR). The proposed antenna consists of a two-port co-linearly polarized antenna and a 2×4 decoupling patch array. Characteristic mode theory indicates that the initial two-port co-linearly polarized antenna exhibits strong coupling because the TM10 mode has equal current amplitude and phase near the two feed probes. This mode can be considered an odd mode. To enhance the isolation between the two ports, a 2×4 decoupling patch array is added, which introduces even modes at low and high frequencies that can cancel out the odd mode, thus achieving broadband decoupling. The prototype measurements indicate the antenna achieves an isolation level of over 20 dB across a 17% fractional bandwidth, offering advantages in broadband decoupling, good radiation performance, and compactness.