A system for transmitting and receiving electromagnetic waves simultaneously. A portion of a signal to be transmitted through a transmitting antenna element is diverted from a transmit signal path, processed by an adjustable filter, and coupled into receive signal path. The adjustable filter is adjusted to approximate the channel that the leakage signals go through to get from the transmitter to the receiver so that the signal coupled into the receiving path through the filter partially cancels the parasitic leakage from the transmit signal path to the receive signal path.