The invention concerns a data acquisition system comprising a circuit for converting a high frequency analog input signal (a) into a plurality of digital signals (D1-DN, R) to be processed by a digital processing system comprising at least one digital processor (8) including a digitizer (1) with m bits, a demultiplexer (2) for delivering in parallel N sampling values with m bits successively supplied by said digitizer (1), a memory (5) for storing the demultiplexed sampling values, said memory (5) being accessible by said digital processing system (8). The invention is characterised in that the circuit further comprises a digital circuit for processing (6) in real time said demultiplexed sampling values, capable of supplying processed results to said digital processing system (8). Said digitizer (1) sampling frequency is higher than said digital processor (8) working frequency.