Concentric Fractal Antenna Arrays For Multiband In-Band Full-Duplex

Enabling multiband systems with per-band in-band full duplexing (IBFD) opens avenues for multiband instantaneous feedback sensing and streaming. This letter adopts fractal antenna arrays to achieve multiband-IBFD (MIBFD) antenna subsystems using hexagonal star array (HSA) geometry as a generating subarray. Characterised by concentric recurring frequency-independent multiband self-interference cancellation (MB-SIC), the HSA enables a frontier MIBFD stage at the antenna domain. Simulation results confirm this hypothesis using three separately fed 4.9, 5.0 and 5.1 GHz signals as test pilots, which achieved -35.5, -42 and -37 dB SIC respectively and simultaneously. The integrated SIC bandwidth within the band is extended to 4.45 <-> 5.85 GHz below −35.5 dB.