APPARATUS FOR DUPLEXING SIGNALS, WIRELESS COMMUNICATIONS DEVICE AND METHOD OF DUPLEXING SIGNALS

A duplexing apparatus comprises a reference of impedance settings and corresponding calibration measurements. A controller (128) is arranged to set a variable impedance (130) to a first impedance setting and transmit a first transmit signal at a first transmit frequency and measure a resulting first signal at an output node (116) of a hybrid circuit (114). The controller (128) then selects a second impedance setting, transmits a second transmit signal at a second transmit frequency and measures a resulting second signal at the output node (116). The controller (128) then determines a balancing result using a system of equations associating the first and second measured signals, and first and second calibration measurements from the reference in respect of the first and second impedance settings, respectively. A third impedance setting is retrieved from the reference by reference to the balancing result to provide isolation of an input node (112) from the output node (116) of the hybrid circuit (114).