Digital filtering method, corresponding circuit and device

A method comprising:

• receiving an input digital signal comprising a sequence of samples;
• applying the input digital signal to digital filter processing with a corner frequency to produce a filtered output digital signal, the digital filter processing comprising a set of multiplication operations using a set of filter multiplication coefficients;
• performing the set of multiplication operations by alternately using a first set of approximate multiplication coefficients and a second set of approximate multiplication coefficients different from the first set of approximate multiplication coefficients;
• wherein the approximate multiplication coefficients in the first set of approximate multiplication coefficients and the second set of approximate multiplication coefficients in the set of filter multiplication coefficients as a function of negative power-of-two values;
• and
• wherein performing the set of multiplication operations results in digital filter processing with average corner frequency approximating the corner frequency, wherein each of the approximate multiplication coefficients of the first and second sets are different from respective filter multiplication coefficients of the set of filter multiplication coefficients, and wherein the average corner frequency approximating the corner frequency is different from the corner frequency.

A circuit, comprising:

• an input node configured to receive an input digital signal comprising a sequence of samples;
• a digital filter processor coupled to the input node to receive the input digital signal, the digital filter processor comprising a set of bit shifting circuit blocks configured to perform a set of multiplication operations and a plurality of switching circuit blocks;
• wherein the multiplication operations are performed by alternately using a first set of approximate multiplication coefficients and a second set of approximate multiplication coefficients different than the first set of approximate multiplication coefficients;
• wherein the approximate multiplication coefficients in the first set of approximate multiplication coefficients and the second set of approximate multiplication coefficients approximate filter multiplication coefficients in a set of filter multiplication coefficients as a function of negative power-of-two values, wherein each of the approximate multiplication coefficients of the first and second sets are different from respective filter multiplication coefficients of the set of filter multiplication coefficients;
• wherein the filter multiplication coefficients define a corner frequency and the approximate multiplication coefficients define an approximate corner frequency that approximates the corner frequency, the approximate corner frequency being different from the corner frequency;
• wherein the bit shifting circuit blocks include bit shifting circuit elements configured to performed the multiplication operations by bit shifting;
• and
• wherein the switching circuit blocks are provided active with the bit shifting circuit blocks to implement alternating multiplication operations with the first set of approximate multiplication coefficients and the second set of approximate multiplication coefficients.

A method comprising:

• receiving an input digital signal comprising a sequence of samples;
• determining a set of filter multiplication coefficients that can be used for filtering the input digital signal;
• determining a first set of approximate multiplication coefficients and a second set of approximate multiplication coefficients based on the filter multiplication coefficients, the first and second sets of approximate multiplication coefficients having negative power-of-two values;
• and
• performing a set of multiplication operations by alternately using the first set of approximate multiplication coefficients and the second set of approximate multiplication coefficients, wherein the set of filter multiplication coefficients define a digital filter with a corner frequency and wherein performing the set of multiplication operations result in digital filter processing with average corner frequency approximating but different than the corner frequency.