US 11,706,062 B1Granted

Digital filter

AssigneeDialog Semiconductor GmbH

InventorsAshley Hughes, Wessel Harm Lubberhuizen

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Abstract

A digital filter for filtering a pulse density modulation (PDM) signal is presented. The filter has a first filter circuit to receive an input signal and to provide a filtered input signal at successive time steps which include a first filtered value at the first time step and a second filtered value at a second time step. The filter also has a quantizer to provide an output signal comprising output values at successive time steps and a filter variable circuit with a first multiplication circuit to receive the first filter variable, and divide the first filter variable by a first gain factor and a first summing circuit configured to receive the divided first filter variable, receive the output signal, and add the divided first filter variable and the first output value and a second multiplication circuit and a delay circuit.

Claims20

Dependent claims

A digital filter comprising:

a) a first filter circuit configured to:
i) receive an input signal comprising input values at successive time steps which include a first input value at a first time step and a second input value at a second time step;
and
ii) provide a filtered input signal comprising filtered values at successive time steps which include a first filtered value at the first time step and a second filtered value at a second time step, the first filtered value being provided by applying a first filter variable to the first input value and the second filtered value being provided by applying a second filter variable to the second input value;
b) a quantizer configured to provide an output signal comprising output values at successive time steps which include a first output value at the first time step and a second output value at the second time step, the output signal being provided by quantising the filtered input signal;
and
c) a filter variable circuit comprising:
i) a first multiplication circuit configured to:
receive the first filter variable;
and
divide the first filter variable by a first gain factor;
ii) a first summing circuit configured to:
receive the divided first filter variable;
receive the output signal;
and
add the divided first filter variable and the first output value
iii) a second multiplication circuit configured to:
receive the sum of the divided first filter variable and the first output value;
and
multiply the sum of the divided first filter variable and the first output value by the first gain factor;
iv) a delay circuit configured to:
receive the sum of the divided first filter variable and the first output value multiplied by the first gain factor;
and
provide the second filter variable to the first filter circuit, the second filter variable being equal to the sum of the divided first filter variable and the first output value multiplied by the first gain factor;
wherein:
the first filter variable and the second filter variable are representative of one or more frequency components to be attenuated in the input signal.

23 more elements

A method of digital filtering an input signal to provide an output signal, the method comprising:

receiving the input signal comprising input values at successive time steps which include a first input value at a first time step and a second input value at a second time step using a first filter circuit;
providing a filtered input signal comprising filtered values at successive time steps which include a first filtered value at the first time step and a second filtered value at a second time step, the first filtered value being provided by applying a first filter variable to the first input value and the second filtered value being provided by applying a second filter variable to the second input value using the first filter circuit;
providing an output signal comprising output values at successive time steps which include a first output value at the first time step and a second output value at the second time step, the output signal being provided by quantising the filtered input signal using a quantizer;
receiving the first filter variable using a first multiplication circuit;
dividing the first filter variable by a first gain factor using the first multiplication circuit;
receiving the divided first filter variable using a first summing circuit;
receiving the output signal using the first summing circuit;
adding the divided first filter variable and the first output value using the first summing circuit;
receiving the sum of the divided first filter variable and the first output value using a second multiplication circuit;
multiplying the sum of the divided first filter variable and the first output value by the first gain factor using the second multiplication circuit;
receiving the sum of the divided first filter variable and the first output value multiplied by the first gain factor using a delay circuit;
and
providing the second filter variable to the first filter circuit using the delay circuit, the second filter variable being equal to the sum of the divided first filter variable and the first output value multiplied by the first gain factor;
wherein:
the first filter variable and the second filter variable are representative of one or more frequency components to be attenuated in the input signal.

12 more elements

Dependencies are inferred from the claim text.