Notch filter with successive windowed integrations, related band-pass filtering device, frequency detection system and processing method

An electronic band-pass filtering device, able to receive an input signal and deliver an output signal having an amplitude, outside a frequency band centered around a target frequency, that is attenuated with respect to that of the input signal, the device comprising:

• a notch filter, able to receive the input signal and deliver a filtered signal having an amplitude, at a cutoff frequency, attenuated with respect to that of the input signal,
• a control module configured to:
• control the notch filter with the cutoff frequency equal to one among a first cutoff frequency and a second cutoff frequency, and store one signal obtained among a first filtered signal related to the first cutoff frequency and a second filtered signal related to the second cutoff frequency, the first cutoff frequency being substantially equal to the target frequency, the second cutoff frequency being distinct from the first cutoff frequency, and
• then control the notch filter with the cutoff frequency equal to the other one among the first cutoff frequency and the second cutoff frequency, in order to obtain the other signal among the first filtered signal and the second filtered signal,
• a generation module, connected to the output of the control module and configured to generate the output signal from a combination of the first and second filtered signals, wherein the notch filter comprises:
• an integration module, configured to integrate of the input signal during several successive time windows, each time window starting at a respective initial time instant and having a duration substantially equal to the inverse of the cutoff frequency, with the initial time instants of at least two distinct windows separated by a time shift of value greater than or equal to a predefined reference duration, each integration of the input signal during a respective time window resulting in a respective intermediate signal,
• a summing module, connected to the output of the integration module and configured to add up the intermediate signals coming from the integration module, the filtered signal depending on the sum of said intermediate signals.

A method for processing an input digital signal, the input digital signal being able to be supplied by an analog-to-digital converter connected to the output of a sensor able to receive an input analog signal, the method being implemented by computer and comprising:

• a notch filtering the input digital signal into a filtered digital signal, the filtered digital signal having an amplitude, at a cutoff frequency, attenuated with respect to that of the input digital signal,
• the notch filtering comprising:
• integrating the input digital signal during several successive time windows, each time window starting at a respective initial time instant and having a duration substantially equal to the inverse of the cutoff frequency, the initial time instants of at least two distinct windows being separated by a time shift of value greater than or equal to a predefined reference duration, each integration of the input digital signal during a respective time window resulting in a respective intermediate digital signal, and
• summing of the intermediate digital signals, the filtered digital signal depending on the sum of said intermediate digital signals;
• wherein the method comprises a band-pass filtering for filtering the input digital signal into an output digital signal, the output digital signal having an amplitude, outside a frequency band centered around a target frequency, that is attenuated with respect to that of the input digital signal, the band-pass filtering comprising:
• an initial implementation of the notch filtering with the cutoff frequency equal to one among a first cutoff frequency and a second cutoff frequency, the first cutoff frequency being substantially equal to the target frequency the second cutoff frequency being distinct from the first cutoff frequency;
• storing the signal obtained among a first filtered digital signal related to the first cutoff frequency and a second filtered digital signal related to the second cutoff frequency, and
• a subsequent implementation of the notch filtering with the cutoff frequency equal to the other one among the first cutoff frequency and the second cutoff frequency, in order to obtain the other signal among the first filtered digital signal and the second filtered digital signal;
• generating the output digital signal from a combination of the first and second filtered digital signals.