In-Band Full-Duplex Self-Interference Canceller Augmented with Bandstop-Configured Resonators

In-band full-duplex transceivers are critical to achieve the efficiency required in next generation communication systems. However, realizing this approach is difficult due to the presence of large self-interference. This paper investigates a novel approach of adaptive analog self-interference cancellation in practical systems by simultaneously leveraging key benefits of different cancellation approaches. A prototype built using a two-tap delay canceller for coarse self-interference response matching and two notch filters for fine point response adjustments demonstrates measured results. In a test scenario, this approach improves 20 dB cancellation bandwidth at 2.4 GHz from 30 MHz to 120 MHz. This is the largest reported adaptive analog isolation at this bandwidth and proves the benefits of using both time and frequency domain cancellation methods to improve bandwidth in practical communication systems.