Highly Integrated In-Band Full-Duplex TRx Antennas for mmWave V2X Communications

A compact mmWave co-circularly polarized (CP) Tx and Rx (TRx) antenna array for in-band full-duplex (IBFDX) V2X communications is proposed. The proposed TRx antenna is based on highly integrated coplanar TRx antenna elements with high Tx-to-Rx isolation maintained in n257 5G NR band. The TRx antenna elements are coplanar patches with the same CP and concentrically integrated to form individual 2 × 2 array on the same substrate. The proposed mmWave IBFDX antenna is designed at 28 GHz with a multilayered printed circuit board (PCB) having sequetially rotated feed networks. Also, the designed antenna is fabricated with the size of 1.867 λ
₀
× 1.867 λ
₀
× 0.087 λ
₀
including both CP feed network and ground plane. The measured 2 × 2 Tx impedance bandwith and peak gain at 28 GHz are 27.14% and 8.43 dBic, respectively. Also, the measured 2 × 2 Rx impedance bandwith and peak gain at 28 GHz are 28.57% and 6.17 dBic, respectively. Further, IBFDX operation of the proposed antenna is verified by n257 5G NR 256-QAM test signals with the maximum 400 MHz bandwidth.