SIW based Antennas for In-Band Full Duplex Communication

Abstract

Mobile subscriptions and the corresponding data traffic has been increasing exponentially over the last decade. To meet these requirements, aggressive research is underway to enhance available bandwidths thereby boosting channel capacity and find ways for supporting more users within the same bandwidth. To that end, simultaneous transmission and reception of data at the same carrier frequency is one such approach. Dubbed as In-band full duplex or IBFD, this model has primary challenge of self-interference (SI) which is the direct coupling of transmitted signals to the receiver side, resulting in masking of the desired receive signals. This work presents substrate integrated waveguide (SIW) based antenna system at 28 GHz for mitigation of SI in propagation domain. SIW is beneficial for in-plane IBFD antenna systems as it is immune to leakage radiation and cross talk irrespective of substrate’s low Dk (dielectric constant) used for antenna design. To the best of author’s knowledge, the first 28 GHz SIW differential antenna with SIW feed is designed and the adopted design procedure is applicable to SIW cavity based differential components design. The antenna utilizes TE201 mode occupying 7 × 7 mm2 and has one single ended port for Tx and one differential pair port for Rx. The radiating part consists of two perpendicular slots etched on the antenna’s top surface and is dual linear polarized capable to transmit and receive simultaneously with gain 8.5 dB over a 444 MHz impedance bandwidth. Next, a 28 GHz SIW based power combiner using TE101 mode featuring an SIW feed and occupying 4.6 × 4.6 mm2 for cancellation of antenna’s SI and extraction of desired Rx signals is implemented. It has one single ended port and one differential pair port. The insertion loss introduced by this power combiner is ≈1.7 dB over 1.9 GHz bandwidth. The peak cancellation of SI is >40 dB. Lastly, the integrated 28 GHz SIW antenna system is presented for IBFD which is in-plane SIW based inter-connection of antenna and power combiner in an over all footprint of 28.6 × 45.8 mm2 . This SIW antenna system has two ports, one for Tx and the other for Rx with gains 8.1 dB and 3.42 dB respectively. The overall peak SiC achieved is ≈53 dB which makes the proposed system suitable for practical 5G IBFD implementations.