18.1 A 1.7-to-2.2GHz full-duplex transceiver system with >50dB self-interference cancellation over 42MHz bandwidth

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

“…The effective OOB IIP3 of the receiver was improved from 14 dBm with the canceler disabled to 35 dBm with the canceler enabled. This work is benchmarked against prior works focussing on SI cancellation for FDD and full-duplex systems [12,18,20,21] as shown in Table 1. The system achieves low noise figure and high effective IIP3 thanks to the improvement of the canceler cross-modulation distortion, while dissipating low power.…”

“…Nonetheless, the nonlinearities of the canceller are also very important and can easily become the bottleneck for the entire receiver. To illustrate this issue, we refer to proposed in [21], where SIC is carried out at baseband. Furthermore, the introduction of a downconversion mixer in the SIC path may cause reciprocal mixing with the LO phase noise, further increasing the RX noise.…”

“…The use on an auxiliary transmitter allows to more than 25 dB of leakage suppression, which highlights an intrinsic linearity limitation from the canceler. A low-power mixer-first receiver with passive mixer based self-interference cancellation is proposed in [21] for dual antenna FD. It handles a SI of up to −10 dBm and 25 dB of suppression is achieved over a limited bandwidth.…”

“…The SI cancellation is done after the mixer, hence, reciprocal mixing is an issue for this architecture. A passive canceler based on an analog FIR filter in the RF side and another FIR filter in the baseband was proposed by [21] for dual antenna FD systems. The FIR filter taps consist basically of a true-time-delay circuit, a buffer and a variable gain amplifier.…”

“…It was shown in [17] that in a typical multi-antenna handset configuration, the group delay of the SI path due to antenna coupling is typically in the order 2-3 ns and that, this limits the achievable cancellation to about 20 dB over a bandwidth of 10 MHz. Improved cancellation bandwidth may be achieved integrating an analog delay line in the canceller as proposed in [21] or using an additional digital cancellation path, as advocated in Figure 1, due to space limitations issues related to limited cancellation bandwidth as a result of larger antenna group delay are left for future work. This paper is organized as follows: Section 2 describes the system architecture and the system level requirements of the receiver chain.…”