Wideband Self-Adaptive RF Cancellation Circuit for Full-Duplex Radio: Operating Principle and Measurements

Abstract

Abstract-This paper presents a novel RF circuit architecture for self-interference cancellation in inband full-duplex radio transceivers . The developed canceller is able to provide wideband cancellation with waveform bandwidths in the order of 100 MHz or beyond and contains also self-adaptive or self-healing features enabling automatic tracking of time-varying self-interference channel characteristics. In addition to architecture and operating principle descriptions, we also provide actual RF measurements at 2.4 GHz ISM band demonstrating the achievable cancellation levels with different bandwidths and when operating in different antenna configurations and under low-cost highly nonlinear power amplifier. In a very challenging example with a 100 MHz waveform bandwidth, around 41 dB total cancellation is obtained while the corresponding cancellation figure is close to 60 dB with the more conventional 20 MHz carrier bandwidth. Also, efficient tracking in time-varying reflection scenarios is demonstrated.

Performance Limitations Analysis of Imperfect Attenuators for Adaptive Self-Interference Cancellation Systém

“…It is noticed that s I (t) and d(t) occupy different frequency bands. The self-interference s I (t) and received signal r (t) can be written respectively as [15] …”

On Performance of Analog Least Mean Square Loop for Self-Interference Cancellation in In-Band Full-Duplex OFDM Systems

“…The multi-tap mechanism, however, suffers the difficulty of calculating weight coefficients to adaptively adjust the phase and amplitude of the cancellation signal. Specifically, an additional digital algorithm is required [3], [5] or a down-conversion is applied to convert RF signals to baseband for adaptive control [9], [10]. Obviously, these approaches not only suffer problems of complexity and power consumption, but, more importantly, also introduce more noise and interference due to the additional local oscillators.…”

A Low-Power Active Self-Interference Cancellation Technique for SAW-Less FDD and Full-Duplex Receivers

“…Alternatively, isolation can be achieved using separate antennas for transmitter and receiver. This basic isolation can be improved using RF cancelation architectures, either based on an RF canceller [3,4] or on an auxiliary transmitter [5]. The use on an auxiliary transmitter allows to more than 25 dB of leakage suppression, which highlights an intrinsic linearity limitation from the canceler.…”