An inphase/quadrature (I/Q) mixer in a homodyne radar system, comprising: a radio frequency input for receiving an RF signal; a local oscillator input for receiving a LO signal; a first mixer unit receiving the RF signal at a first input of the first mixer unit; and a second mixer unit receiving the RF signal at a first input of the second mixer unit; the system being characterised by: a plurality of phase shifters (17, 118, 120) for applying a selectable phase shift to the LO signal to produce a first phase-shifted version of the LO signal and a second phase-shifted version of the LO signal, the first and second phase-shifted versions of the LO signal being in quadrature; a first set of switches (112, 114) being controllable to selectively apply the selectable phase shift to the LO signal; a second set of switches (102, 104, 106, 108) being controllable to apply selectively either one of the first and second phase-shifted versions of the LO signal to one of a second input of the first mixer unit and a second input of the second mixer unit and to apply the other of the first and second phase-shifted versions of the LO signal to the other of the second input of the first mixer unit and the second input of the second mixer unit; and a counter for generating a count, the count sequencing through states of the first (112,114) and second (102, 104, 106, 108) sets of switches. a radio frequency input for receiving an RF signal; a local oscillator input for receiving a LO signal; a first mixer unit receiving the RF signal at a first input of the first mixer unit; and a second mixer unit receiving the RF signal at a first input of the second mixer unit; the system being characterised by: a plurality of phase shifters (17, 118, 120) for applying a selectable phase shift to the LO signal to produce a first phase-shifted version of the LO signal and a second phase-shifted version of the LO signal, the first and second phase-shifted versions of the LO signal being in quadrature; a first set of switches (112, 114) being controllable to selectively apply the selectable phase shift to the LO signal; a second set of switches (102, 104, 106, 108) being controllable to apply selectively either one of the first and second phase-shifted versions of the LO signal to one of a second input of the first mixer unit and a second input of the second mixer unit and to apply the other of the first and second phase-shifted versions of the LO signal to the other of the second input of the first mixer unit and the second input of the second mixer unit; and a counter for generating a count, the count sequencing through states of the first (112,114) and second (102, 104, 106, 108) sets of switches. a plurality of phase shifters (17, 118, 120) for applying a selectable phase shift to the LO signal to produce a first phase-shifted version of the LO signal and a second phase-shifted version of the LO signal, the first and second phase-shifted versions of the LO signal being in quadrature; a first set of switches (112, 114) being controllable to selectively apply the selectable phase shift to the LO signal; a second set of switches (102, 104, 106, 108) being controllable to apply selectively either one of the first and second phase-shifted versions of the LO signal to one of a second input of the first mixer unit and a second input of the second mixer unit and to apply the other of the first and second phase-shifted versions of the LO signal to the other of the second input of the first mixer unit and the second input of the second mixer unit; and a counter for generating a count, the count sequencing through states of the first (112,114) and second (102, 104, 106, 108) sets of switches.