Remote Sensing of Bio-Signals

An apparatus (10) for performing a remote measurement of a bio-signal of a subject, the device comprising: at least one radar signal transmitter (14) configured to transmit at least a first radar signal at a first carrier frequency and a second radar signal at a second carrier frequency; at least one signal receiver (16) configured to receive at least one radar return signal; detection circuitry (18) coupled to the signal receiver, wherein the detection circuitry (18) is configured to produce at least one first detection signal for the first carrier frequency and at least one second detection signal for the second carrier frequency in response to receiving the at least one radar return signal at the signal receiver (16), wherein the first carrier frequency and the second carrier frequencies are such that the at least one first and/or the at least one second detection signals comprise a contribution from the bio-signal and a contribution from a further bio-signal and/or a background; and signal combining circuitry (20) configured to perform a signal combining process with the at least one first detection signal and the at least one second detection signal to produce at least one combined signal comprising an at least reduced contribution from the further bio-signal and/or background.