A SAW-less receiver front-end with low power active self-interference canceler

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

“…Canceling the SI after the LNA, e.g., as proposed in [25], could result in LNA clipping and receiver desensitization at large SI levels. Similar considerations apply to the SI architecture proposed in [22], where SIC is carried out at baseband. Furthermore, the introduction of a down-conversion mixer in the SIC path may cause reciprocal mixing with the LO phase noise, further increasing the RX noise.…”

“…A 40 MHz cancellation bandwidth was achieved over a 50 dB leakage cancellation, however at the expense of high power consumption and noise degradation which scales with the number of FIR taps. This paper describes an active SI cancellation technique for a SAW-less diversity receiver, extending the conference publication [22]. In this work, the design is extended including the downconversion mixers and baseband trans-impedance amplifiers (TIAs).…”

“…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 [22] 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.…”

“…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 [22] for dual antenna FD systems. The FIR filter taps consist basically of a true-time-delay circuit, a buffer and a variable gain amplifier.…”