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 from 30 MHz to 120 MHz. This is the largest adaptive analog isolation improvement for >80 MHz bandwidth and proves the benefits of using both time and frequency domain cancellation methods to improve bandwidth in practical communication systems.