Antenna coupling and self-interference cancellation bandwidth in SAW-less diversity receivers

Self-interference (SI) cancellation techniques are a promising solution to improve the dynamic range of SAW-less frequency-division duplexing (FDD) diversity receivers. The achievable isolation between transmitter and diversity receiver over the transmit signal bandwidth is limited by the strength and frequency selectivity of the coupling between main and diversity antennas. In this work we investigate these limitations under realistic conditions for long-term evolution (LTE) mobile terminals. A pair of planar inverted-F antennas (PIFAs) has been designed and tested in four different configurations. A broadband current-mode canceler model was applied to the measured data showing, in all cases, a 20dB cancellation bandwidth of 14MHz, mainly limited by the antennas y
₂₁
group delay, close to 2ns.