Optoelectronic Integrated RF Self-Interference Cancellation Chip with Phase Tunability for In-Band Full-Duplex Communications

In-band full-duplex (IBFD) technology suffers from strong radio frequency (RF) self-interference, which limits its potential to double spectral efficiency and transmission rate. This paper proposes a phase-tunable optoelectronic integrated scheme for RF self-interference cancellation (SIC). With a footprint of 1.8 × 4.2 mm 2, the chip incorporates a microwave photonic (MWP) phase shifter (comprising a phase modulator, an optical filter, and a thermally tuned waveguide), as well as amplitude and delay adjustors based on a Mach–Zehnder interferometer and a spiral waveguide. Unlike traditional dual MWP path schemes, this scheme reconstructs the reference signal in the optical domain while keeping the received signal (with interference) in the electronic domain, avoiding signal degradation. The experimental results show that the on-chip scheme achieves 25 dB cancellation depth over a 0.4 GHz bandwidth with a frequency band of 11–19 GHz. In over-the-air IBFD communication with antennas, the cancellation depth of 20 dB over a 300 MHz bandwidth at a central frequency of 12.4 GHz is measured, with successfully recovering the signal of interest. By virtue of the optoelectronic integration property, the proposed scheme significantly enhances the receiving sensitivity, linearity, reduces the noise figure, and paves the way for the real application of photonic-enabled RF SIC technique.