Dual-Polarized Cavity-Backed Full Metal Antennas for In-Band Full-Duplex Application

In this article, a decoupling network is proposed for the design of in-band full-duplex antennas, whereby high isolation between the transmitter (Tx) and receiver (Rx) ports is attained by adjusting the coupling within the antenna to generate transmission zeros in the passband. To guide antenna design, analyses are carried out on both first-order and third-order decoupling networks. A first-order full-duplex antenna is designed based on a slot antenna array and a metal block antenna, which are capable of obtaining a transmission zero in the passband. A third-order full-duplex antenna is designed based on a TM120/210 mode cavity and a cross-shaped radiant metal block, which obtains three transmission zeros in the passband. The internal coupling relationships of the antennas are analyzed in detail, and two full-duplex antennas are fabricated and measured. The measured results demonstrate that the isolation between the Tx antenna and Rx antenna is greater than 30 dB in the passband.