Substrate integrated waveguide antenna system for 5g in-band full duplex applications

In-band full duplex offers a new approach of meeting the ever-increasing data rate demands by operating the transmitter and receiver at the same frequency at the same time, potentially doubling the spectral efficiency. However, self-interference is the fundamental bottleneck of such systems. In contrast to non-planar or sub 6 GHz microstrip designs reported so-far, this paper presents an all SIW based antenna system for in-band full duplex systems. The proposed design integrates a dual linear polarized three port differential antenna, three port SIW common-mode power combiner and a 180°phase shifter at 28 GHz. Operating the antenna in TE201 mode provides inherent isolation between the differential receive and single-ended transmit port. The residual coupling is further reduced through use of TE101 based power combiner and a 180°phase shifter. Implemented on a 0.508 mm thick RT Duroid 5880 substrate, the antenna occupies a foot-print of 48 × 80 mm² . Demonstrating a measured gain of 6.95 dBi and 3.42 dBi for Tx and Rx mode of operation, respectively, the proposed design offers a self-interference cancellation (SiC) of better than 36 dB over a 177 MHz bandwidth.