Dual-Band Full-Duplex Tx/Rx Antennas for Vehicular Communications

This paper proposes a novel dual-band full-duplex antenna/array for intelligent transport systems applications. Different from traditional single-port single-band antennas, the two ports of the antenna are highly isolated and designed to operate at different frequency bands simultaneously. Such a property could support the full-duplex operation-mode, which significantly simplifies the complexity of the RF frontend subsystem. The other contribution of this work is that multiple functions such as filtering, duplexing, and radiation are combined into one single device, resulting in a simplified RF frontend. This co-design multifunctional device could also remove the separate filters, duplexers, and interfaces between them, resulting in the reduction of the size, weight, and cost. In addition, cross-coupling is investigated and employed to generate additional transmission zeros so as to improve the channel isolation and out-of-band interference. To verify the concept, an antenna element and two 2 × 2 arrays at C-band are designed, prototyped, and tested. All the measurements agree well with the simulations, showing two full-duplex channels of 4.58-4.83 GHz and 5.86-6.2 GHz for transmitting and receiving, respectively. The proposed antennas also exhibit excellent performance in terms of channel isolations, frequency selectivity, out-of-band rejections, and gains.