appear at the output of the low pass filter and in consequence form the in phase signal or the in phase component i t in this analysis it has been assumed that the input signal v t is a signal in the form of a cosine wave proportional to cos u03c9t in the same way the lower path of the mixing circuit 3 illustrated in fig1 comprises the multiplier unit 7 which however is supplied with a signal sin u03c9t in the form of a sine wave in consequence both components at the difference frequency u03c9 0 u2212 u03c9 and components at the sum frequency u03c9 0 u03c9 are produced at the output of the multiplier unit 7 the low pass filter lpf is once again designed such that only the components at the difference frequency are produced at the output of the low pass filter and form the quadrature component q t assuming that the input signal v t is in the form of a cosine wave the quadrature component q t thus comprises a signal in the form of a sine wave at the difference frequency u03c9 0 u2212 u03c9 the in phase component i t and the quadrature component q t are each supplied to one input of the quadricorrelator 5 the quadricorrelator 5 in each case comprises a straight through path for the in phase component i t and the quadrature component q t with a multiplier unit 9 or 11 respectively being located in each straight through path an output signal c from the multiplier unit 9 in the straight through path for the in phase.