Disclosed is an apparatus (100) for high sensitivity phase detection of an
electric signal by means of a
local oscillator. The apparatus (100) comprises a first mixer unit (110) with a first
electric signal connector (111), a first
local oscillator connector (112), a first output connector (113), and a first reference connector (114), and the apparatus (100) comprises a second mixer unit (120) with a second
electric signal connector (121), a second
local oscillator connector (122), a second output connector (123), and a second reference connector (124). The first mixer unit (110) and the second mixer unit (120) are each configured to mix the electric
signal with the local oscillator and based thereon produce an output with respect to a potential at the first reference connector (114) or second reference connector (124), respectively. The apparatus comprises a link (140) between the first output connector (113) and the second reference connector (124). The link (140) is configured to provide an input to the second reference connector (124) which is based on an output of the first output connector (113).