Active Cancellation Limitation Analysis for Full Duplex Systems with a Single Antenna

In this paper the performance limitations of the multi-PA / multi-LNA / single-antenna duplex RF transceiver architecture interconnected by a passive reciprocal electrical network are explored. It is shown that, if the antenna's impedance is allowed to change, as is the case in real environment, either the influence of the PAs' signal output on the SNR or the influence of the PAs' thermal noise on the SNR can be canceled, but not both of them simultaneously. Additionally, it is demonstrated that, if the antenna's impedance is fixed, then it is possible to design a system in which both the SNR impact of the PAs' signals and the SNR impact of the PAs' thermal noise are canceled. The constraint on the amount of the LNAs and the PAs required to achieve this cancellation is demonstrated as well.