Fundamental Efficiency Limit of Passive Non-Magnetic Self-Interference Suppression in Full-Duplex Radios

Passive non-magnetic self-interference suppression circuits are currently used as first stages of complex full-duplex radio systems that allow simultaneous reception and transmission within the same channel. This paper introduces the upper efficiency limit for such circuitry. It is demonstrated that for these devices it is not feasible to have simultaneously high efficiency, good transmitter-to-receiver isolation and same propagation channel for transmission and reception. More specifically, the maximum efficiency for most typical case cannot exceed 50% if good isolation is obtained