EBG enhanced broadband dual antenna configuration for passive self-interference suppression in full-duplex communications

A full-duplex system is realised using dual EBG isolated rectangular spiral antennas and its performance is compared with the same full-duplex system using a circulator and a single spiral antenna element. The new antenna system consists of two antennas one with RHCP and the another one with LHCP implemented on a single substrate. Two columns of EBG is placed between the two antennas to improve the isolation. At the operating frequency of 3.2 GHz, the antenna configuration has nearly 31 dB isolation. For the identical baseband input power, the full-duplex system utilising dual spiral antenna configuration exhibits 9 dB higher isolation than the circulator based full-duplex system

Passive Self-Interference Suppression for Single Channel Full-Duplex Operation

Full duplex radios have become a topic of increased interest in the wireless communications community. As part of this development, many efforts were directed to passively decrease the self-interference level at the antenna outputs. However, in many proposed solutions transmission and reception occur through different propagation channels. This paper demonstrates and quantifies the negative impact of channel differentiation on pivotal applications of full-duplex radio, such as cognitive radio. Antenna designs used for self-interference suppression in full-duplex radio architectures are analyzed. In order to ensure that transmission and reception occur within the same propagation channel, the use of the envelope correlation coefficient is proposed. The paper aims to firstly define the problem and proposes a metric to quantitatively assess full-duplex antenna designs. This is followed by analysis and discussion of representative full-duplex solutions (i.e. their antenna and passive RF feed components) proposed in the literature. Finally, it is demonstrated for the first time, that the passive non-magnetic self-interference suppression comes at the cost of increased losses in the structure. A theoretical upper limit for the antenna efficiency is proposed. Its consistency is verified for three representative full-duplex antenna designs which are highly documented in the literature

Full-Duplex Systems Using Multireconfigurable Antennas

Full-duplex systems are expected to achieve 100% rate improvement over half-duplex systems if the self-interference signal can be significantly mitigated. In this paper, we propose the first full-duplex system utilizing multireconfigurable antenna (MRA) with ∼90% rate improvement compared with half-duplex systems. MRA is a dynamically reconfigurable antenna structure that is capable of changing its properties according to certain input configurations. A comprehensive experimental analysis is conducted to characterize the system performance in typical indoor environments. The experiments are performed using a fabricated MRA that has 4096 configurable radiation patterns. The achieved MRA-based passive self-interference suppression is investigated, with detailed analysis for the MRA training overhead. In addition, a heuristic-based approach is proposed to reduce the MRA training overhead. The results show that at 1% training overhead, a total of 95 dB self-interference cancelation is achieved in typical indoor environments. The 95-dB self-interference cancellation is experimentally shown to be sufficient for 90% full-duplex rate improvement compared with half-duplex systems