A new four-port dual-polarized antenna and array are presented for In-Band Full-Duplex (IBFD) applications, offering high inter-port isolation. The single-element antenna system consists of four H-shape slots, stacked patches for wide bandwidth, and two external hybrid couplers. The multilayer antenna is well matched from about 2.1 to 2.4 GHz and provides high isolation in this frequency range in excess of 60 dB. Two different prototypes are simulated and measured to highlight the design process. In addition, a new and compact hybrid coupler with excellent phase and magnitude stability is also presented for improved antenna radiation and IBFD performances. When compared to other similar types of hybrid coupler and antenna systems, the proposed configurations are simple to manufacture, provide a higher isolation bandwidth (10%), and higher gain of 7.3 dBi with cross-polarization levels of 30 dB or lower. The single-element design was also extended to a 2×2 array and studied for different beam steering and feeding scenarios. The operating bandwidths and isolation values offered by these S-band antenna and array systems can support new data link possibilities for beam steering and future low-cost IBFD wireless networks by simple antenna fabrication.

A new two-port dual-polarized planar antenna with an integrated feeding circuit for in-band full-duplex (IBFD) applications is presented. The antenna consists of four H-shape slots, stacked patches for enhanced bandwidth (BW), and a separate layer of two differential (0 • and 180 • split) power dividers connected using vertical transmission lines which define the feeding system. The multilayer antenna is well matched from about 2.2 to 2.5 GHz with isolation values from about 40 to 60 dB. When compared to similar IBFD antenna systems, the proposed configuration provides a higher isolation BW (10%) and higher gain (7.8 dBi) whilst adopting a simple feeding network. Also, by using the proposed feeding circuit, the manufactured antenna does not require any external cables and couplers. This simplifies the structure and reduces the amount of cable connections. This allows for other analog-based self-interference reduction schemes for further improvements in the transmit and receive data link. In addition, the proposed antenna design was extended to a 4×1 array. These dual-differential IBFD antenna systems are a good alternative to more conventional full-duplex designs which typically require external coupler-based feeding. In addition, the operating BWs and isolation values offered by these S-band systems can support new data link possibilities for beam steering and future IBFD wireless networks by low-cost antenna and feeding circuit integration.

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