Active interference cancellation apparatus, signal isolation control apparatus and method of actively cancelling interference

An active interference cancellation apparatus for controlling duplex operation of signals to be transmitted and received, the apparatus comprising:

• a receiver chain comprising a received signal input node;
• a transmitter chain comprising a transmitter chain tap node and a transmitter output node;
• an auxiliary transmitter chain having an auxiliary chain input node operably coupled to the transmitter chain tap node, the auxiliary transmitter chain comprising an adaptive filter, a coefficient processor, and a cancellation signal output, the cancellation signal output being operably coupled to the received signal input node of the receiver chain;
• and
• an interpolation processor;
• wherein
• the coefficient processor is operably coupled to the receiver chain and the adaptive filter;
• the interpolation processor is arranged to cooperate with the coefficient processor;
• the transmitter chain is arranged to generate, when in use, a first waveform comprising a first plurality of frequency-separated signals;
• contemporaneously with the transmitter chain, the auxiliary transmitter chain is arranged to generate a second waveform comprising a second plurality of frequency-separated signals and apply the second waveform at the received signal input node;
• the receiver chain is arranged to receive a composite waveform comprising a waveform coupled from the output node of the transmitter chain to the received signal input node of the receiver chain and the second waveform from the auxiliary transmitter chain;
• and
• the first waveform does not comprise any signals required for determination of equaliser coefficients of the adaptive filter that coincide in frequency with the second plurality of frequency-separated signals of the second waveform.