Back to results
US 6,232,900 B1Granted
Second order digital filter requiring only one sigma delta modulator
AssigneeLucent Technologies Inc.
InventorsPaul D. Hendricks, Lane A. Smith
Life of this patent
Estimating the term…
Abstract
A 2nd order digital filter requiring only one sigma delta modulator is created by implementing (1) a 2nd order feedforward term created by the cascade of two 1st order elements; (2) a 2nd order feedback term created by the cascade of two 1st order elements; and (3) another 2nd order feedback term created by the cascade of two more 1st order elements to eliminate the need for another sigma delta modulator to provide a 2nd order filter. Thus, for the mere ‘cost’ of additional feedback loops, which are small in comparison with the size and complexity of another sigma delta modulator, a second sigma delta modulator is not necessary to implement a 2nd order digital filter in accordance with the principles with the present invention.
Claims20
A 2nd order digital filter, comprising:
- a single sigma delta modulator;
- a first 1st order feedback term connected to an output of said single sigma delta modulator;
- a delay element to delay said first 1st order feedback term;
- and
- a summer for summing said delayed first 1st order feedback term with a signal being input to said single sigma delta modulator of said 2nd order digital filter.
2 more elements
A digital filter, comprising:
- a sigma delta modulator;
- a first 1st order feedback term connected to an output of said sigma delta modulator;
- a delay element to delay said first 1st order feedback term;
- a summer to sum said delayed first 1st order feedback term with a signal being input to said sigma delta modulator;
- a second 1st order feedback term connected between an input of said sigma delta modulator and said summer;
- and
- a third 1st order feedback term connected between said second 1st order feedback term and said summer;
- wherein said second 1st order feedback term and said third 1st order feedback term combine to provide a 1st order feedback term and a 2nd order feedback term.
5 more elements
A digital filter, comprising:
- a sigma delta modulator;
- a first 1st order feedback term connected to an output of said sigma delta modulator;
- a delay element to delay said first 1st order feedback term;
- and
- a summer to sum said delayed first 1st order feedback term with a signal being input to said sigma delta modulator;
- a first 1st order feedforward term connected between an input signal to said digital filter and said summer;
- a second 1st order feedforward term connected between said first 1st order feedforward term and said summer;
- a second 1st order feedback term connected between an input of said sigma delta modulator and said summer;
- and
- a third 1st order feedback term connected between said second 1st order feedback term and said summer;
- wherein said first 1st order feedforward term and said second 1st order feedforward term combine to provide a 1st order feedforward term and a 2nd order feedforward term;
- and
- wherein said second 1st order feedback term and said third 1st order feedback term combine to provide a 1st order feedback term and a 2nd order feedback term.
10 more elements
A method of providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- generating a modulated signal with said only one sigma delta modulator;
- delaying a sample output from said sigma delta modulator for one filter cycle;
- and
- summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator.
2 more elements
A method of providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- generating a modulated signal with said only one sigma delta modulator;
- delaying a sample output from said sigma delta modulator for one filter cycle;
- and
- summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator;
- and
- wherein said sigma delta modulator delays a sample for one filter cycle.
4 more elements
A method of providing a 2nd or higher order digital filter using only one sigma delta modulator comprising:
- generating a modulated signal with said only one sigma delta modulator;
- delaying a sample output from said sigma delta modulator for one filter cycle;
- and
- summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- delaying an input sample to said only one sigma delta filter for one filter cycle;
- delaying said delayed input sample for a second filter cycle;
- and
- inputting said twice delayed input sample to said only one sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator;
- and
- wherein a 2nd order numerator portion of a transfer function is provided by said twice delayed input sample.
8 more elements
A method of providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- generating a modulated signal with said only one sigma delta modulator;
- delaying a sample output from said sigma delta modulator for one filter cycle;
- and
- summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- delaying an input sample to said only one sigma delta filter for one filter cycle;
- delaying said delayed input sample for a second filter cycle;
- inputting said twice delayed input sample to said only one sigma delta modulator;
- and
- inputting said once delayed input sample to said only one sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator;
- and
- wherein a 2nd order numerator portion of a transfer function is provided by said twice delayed input sample.
9 more elements
A method of providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- generating a modulated signal with said only one sigma delta modulator;
- delaying a sample output from said sigma delta modulator for one filter cycle;
- and
- summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- delaying said input signal to said only one sigma delta modulator for a first filter cycle;
- delaying said once delayed input signal for a second filter cycle;
- and
- summing said twice delayed input signal with said input to said only one sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator.
6 more elements
A method of providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- generating a modulated signal with said only one sigma delta modulator;
- delaying a sample output from said sigma delta modulator for one filter cycle;
- summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- delaying said input signal to said only one sigma delta modulator for one filter cycle;
- delaying said once delayed input signal for a second filter cycle;
- and
- summing said twice delayed input signal with said input to said only one sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator.
5 more elements
Apparatus for providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- means for generating a modulated signal with one sigma delta modulator;
- means for delaying a sample output from said sigma delta modulator for one filter cycle;
- and
- means for summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator.
2 more elements
Apparatus for providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- means for generating a modulated signal with one sigma delta modulator;
- means for delaying a sample output from said sigma delta modulator for one filter cycle;
- means for summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- means for delaying an input sample to said only one sigma delta filter for one filter cycle;
- means for delaying said delayed input sample for a second filter cycle;
- and
- means for inputting said twice delayed input sample to said only one sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator;
- wherein a 2nd order numerator portion of a transfer function is provided by said twice delayed input sample.
6 more elements
Apparatus for providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- means for generating a modulated signal with one sigma delta modulator;
- means for delaying a sample output from said sigma delta modulator for one filter cycle;
- means for summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- means for delaying an input sample to said only one sigma delta filter for one filter cycle;
- means for delaying said delayed input sample for a second filter cycle;
- means for inputting said twice delayed input sample to said only one sigma delta modulator;
- and
- means for inputting said once delayed input sample to said only one sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator;
- and
- wherein a 2nd order numerator portion of a transfer function is provided by said twice delayed input sample.
8 more elements
Apparatus for providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- means for generating a modulated signal with one sigma delta modulator;
- means for delaying a sample output from said sigma delta modulator for one filter cycle;
- means for summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- means for delaying said input signal to said only one sigma delta modulator for a first filter cycle;
- means for delaying said once delayed input signal for a second filter cycle;
- and
- means for summing said twice delayed input signal with said input to said only one sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator.
5 more elements
Apparatus for providing a 2nd or higher order digital filter using only one sigma delta modulator, comprising:
- means for generating a modulated signal with one sigma delta modulator;
- means for delaying a sample output from said sigma delta modulator for one filter cycle;
- means for summing said delayed sample output from said one sigma delta modulator with an input signal to said sigma delta modulator;
- means for delaying said input signal to said only one sigma delta modulator for one filter cycle;
- means for delaying said once delayed input signal for a second filter cycle;
- and
- means for summing said twice delayed input signal with said input to said only one sigma delta modulator;
- wherein a 2nd order denominator portion of a transfer function is output by said one sigma delta modulator.
5 more elements
Dependencies are inferred from the claim text.