Apparatus and method for tuning a filter

An apparatus (1) for tuning a filter (11) comprising:

• a filter (11) for receiving an input signal (10) and providing an output signal (9,28), the filter adapted to receive a tuning signal (27) to adjust the filter to provide the output signal to a desired signal, the tuning signal resulting from a modulation signal (25), a correction signal (26) and an approximate filter tuning signal (19) generated by a filter tuning signal generator (20), the modulation signal having a frequency that varies between a first frequency (F1) and a second frequency (F2), a first value (S1) of the output signal measured at the first frequency, and a second value (S2) of the output signal measured at the second frequency, a comparator (16) for comparing the first value and the second value and providing the correction signal, to adjust the filter with the tuning control signal with respect to the first frequency and the second frequency of the modulation signal, the correction signal and the approximate filter tuning signal.