Patent ID: 7595476

Claim:
An electrical circuit for the detection of a signal (I) modulated with a modulation frequency, a modulation period being defined as the inverse of the modulation frequency, comprising: transduction means (T) for transducing the modulated signal (I) into an electrical signal, sampling means (S) for sampling said electrical signal with a sampling frequency which is equal to four times the modulation frequency or a multiple thereof, first subtraction means (SUB 1 ) for evaluating a plurality of first difference between two samples per modulation period, each separated by half the modulation period, and second subtraction means (SUB 2 ) for evaluating a plurality of second difference between two samples per modulation period, each separated by half the modulation period, said second samples being time-shifted with respect to said first samples by a defined fraction, preferably a quarter, of the modulation period, characterized by first summation means (SUM 1 ) for evaluating a first sum of a plurality of subsequent first differences evaluated by said first subtraction means (SUB 1 ), and second summation means (SUM 2 ) for evaluating a second sum of a plurality of subsequent second differences evaluated by said second subtraction means (SUB 2 ).