A baseband receiver, consisting of a receiver input port, configured to receive a baseband signal generated in response to electrical activity in tissue of a human patient. The receiver includes a modulator, configured to modulate a local oscillator signal with the baseband signal, and an isolating device configured to receive the modulated local oscillator signal at an input port of the device and in response to generate a modulated output local oscillator signal at an output port of the device. The receiver further includes a demodulator configured to demodulate the modulated output local oscillator signal with the local oscillator signal so as to recover the baseband signal.