Tx-Rx isolation exploiting tunable balanced - Unbalanced antennas architecture

The duplex filter is probably still the most expensive component in mobile handsets for the significant Transmitter (Tx) - Receiver (Rx) isolation required. This paper suggests to relax or even replace the duplex filter by equipping the Tx and the Rx with two separate antennas. The two antennas are different in the sense that one is balanced and the other is unbalanced. By properly controlling the two arms of the balanced antenna, impressive Tx-Rx isolation is obtained by canceling the coupling trans-impedance between the two antennas.