Baseband equalizer for TX leakage cancellation in active duplexing

Today´s multi-mode multi-band smartphones use acoustic wave (SAW/BAW) duplexing filters for each frequency band that it supports. As the number of frequency bands keep growing, such bulky filtering solutions become less feasible; adding to cost and size of smartphones. Adaptive duplexing solutions proposed in literature require multiple RF loops for wideband TX-RX isolation, resulting in large TX powers and low battery life. This paper introduces an alternate approach of using a baseband DSP equalizer on an auxiliary TX branch in combination with a tunable LC-based low-isolation device. Simulations show that a 42 dB TX leakage cancellation can be achieved over 40 MHz bandwidth.