Sigma delta modulator with distributed prefiltering and feedback

Claim 2

A sigma delta modulator for generating an output digital data stream from an analog signal, said modulator comprising: a plurality of filter modules for receiving and processing an error signal; means connecting said filter modules in series; means for injecting a signal between each pair of filter modules; an analog-to-digital converter responsive to an output of said plurality of filter modules for generating said output data stream; a digital-to-analog converter responsive to said output stream for generating a feedback signal; means for summing said analog signal and said feedback signal to generate said error signal; means responsive to said feedback signal for applying a partial feedback signal to each of said injecting means and to said summing means; a plurality of prefilters connected in parallel to said analog input, each of said prefilters generating a partial prefilter signal; and means for applying a partial prefilter signal to each of said injecting means and to said summing means.

Claim 3

A sigma delta modulator according to claim 1 wherein said injecting means comprises a plurality of summing junctions, one of said plurality of summing junctions being connected between each pair of filter modules.

Claim 4

A sigma delta modulator according to claim 2 wherein said frequency-shaping means comprises a plurality of feedback modules, each of said modules generating a partial feedback signal and wherein each of said partial feedback signals is applied to one of said plurality of summing junctions.

Claim 5

A sigma delta modulator according to claim 3 wherein each of said feedback modules is a passive network.

Claim 6

A sigma delta modulator according to claim 3 wherein each of said feedback modules is an active network.

Claim 7

A sigma delta modulator according to claim 1 wherein each of said filter modules is a passive network.

Claim 8

A sigma delta modulator according to claim 1 wherein each of said filter modules is an active network.

Claim 9

A sigma delta modulator for generating an output digital data stream from an analog signal at an analog input, said modulator comprising: a plurality of filter circuits connected as a cascade filter for receiving and processing an error signal; a plurality of summing junctions, one of said plurality of summing junctions being located between each pair of filter circuits in said cascade filter; an analog-to-digital converter responsive to an output of said cascade filter for generating said output data stream; a digital-to-analog converter responsive to said output stream for generating a feedback signal; a plurality of feedback circuits connected as a cascade feedback circuit for receiving and processing said feedback signal, each of said plurality of feedback modules generating one of a plurality of partial feedback signals, means for applying one of said plurality of partial feedback signals to one of said summing junctions; a plurality of prefilters connected in parallel to said analog input, each of said prefilters generating a partial prefilter signal; and means for applying one of said plurality of partial prefilter signals to one of said summing junctions.

Claim 10

A sigma delta modulator for generating an output digital data stream from an analog signal at an analog input, said modulator comprising: a plurality of filter circuits connected as a cascade filter for receiving and processing an error signal; a plurality of summing junctions, one of said plurality of summing junctions being located between each pair of filter circuits in said cascade filter; an analog-to-digital converter responsive to an output of said cascade filter for generating said output data stream; a digital-to-analog converter responsive to said output stream for generating a feedback signal; a plurality of feedback circuits connected as a cascade feedback circuit for receiving and processing said feedback signal, each of said plurality of feedback modules generating one of a plurality of partial feedback signals, means for applying one of said plurality of partial feedback signals to one of said summing junctions; a plurality of prefilters connected in parallel to said analog input, each of said prefilters generating a partial prefilter signal; and means for applying one of said plurality of partial prefilter signals to one of said summing junctions.

Claim 11

A sigma delta modulator according to claim 8 wherein each of said feedback circuits is a passive network.

Claim 12

A sigma delta modulator according to claim 8 wherein each of said feedback circuits is an active network.

Claim 13

A sigma delta modulator according to claim 8 wherein each of said filter circuits is a passive network.

Claim 14

A sigma delta modulator according to claim 8 wherein each of said filter circuits is an active network.

Claim 15

A sigma delta modulator according to claim 8 wherein said analog-to-digital converter comprises a single-bit comparator.

Claim 16

A sigma delta modulator according to claim 8 wherein said digital-to-analog converter comprises a single-bit digital-to analog converter.

Claim 17

A sigma delta modulator according to claim 8 wherein said single-bit digital-to analog converter comprises two reference voltage levels and means responsive to said output stream for selecting one of said reference voltage levels as said feedback signal.

Claim 18

A sigma delta modulator according to claim 8 wherein at least one of said filter circuits is an integrator.

Claim 19

A sigma delta modulator according to claim 8 wherein at least one of said filter circuits is a resonator.

Claim 20

A sigma delta modulator for generating an output digital data stream from an analog signal at an analog input, said modulator comprising: a first summing junction responsive to said analog signal for generating a first error signal; an integrator responsive to said error signal for generating an integrated error signal; a second summing junction responsive to said integrated error signal for generating a second error signal; a resonator network responsive to said second error signal for generating an output error signal; a comparator responsive to said output error signal for generating said output data stream; a selection switch responsive to said output stream for selecting one of two reference voltages as a feedback signal; a first feedback circuit responsive to said feedback signal for generating a first partial feedback signal; means for applying said first partial feedback signal to said second summing junction to be summed with said integrated error signal to generate said second error signal; a second feedback circuit responsive to said first partial feedback signal for generating a second partial feedback signal; means for applying said second partial feedback signal to said first summing junction to be summed with said analog signal to generate said first error signal; a first prefilter connected between said analog input and said first summing junction; and a second prefilter connected between said analog input and said second summing junction.

Claim 21

A sigma delta modulator for generating an output digital data stream from an analog signal at an analog input, said modulator comprising: a first summing junction responsive to said analog signal for generating a first error signal; an integrator responsive to said error signal for generating an integrated error signal; a second summing junction responsive to said integrated error signal for generating a second error signal; a resonator network responsive to said second error signal for generating an output error signal; a comparator responsive to said output error signal for generating said output data stream; a selection switch responsive to said output stream for selecting one of two reference voltages as a feedback signal; a first feedback circuit responsive to said feedback signal for generating a first partial feedback signal; means for applying said first partial feedback signal to said second summing junction to be summed with said integrated error signal to generate said second error signal; a second feedback circuit responsive to said first partial feedback signal for generating a second partial feedback signal; means for applying said second partial feedback signal to said first summing junction to be summed with said analog signal to generate said first error signal; a first prefilter connected between said analog input and said first summing junction; and a second prefilter connected between said analog input and said second summing junction.

Claim 22

A sigma delta modulator according to claim 18 wherein said first feedback circuit is a capacitor.

Claim 23

A sigma delta modulator according to claim 18 wherein said second feedback circuit is a capacitor.

Claim 24

A sigma delta modulator according to claim 18 wherein said integrator is fabricated with switched capacitor technology.

Claim 25

A sigma delta modulator according to claim 18 wherein said resonator is fabricated with switched capacitor technology.

Claim 26

A sigma delta modulator for generating an output digital data stream from an analog signal, said modulator comprising: a filter network for receiving and processing an error signal; an analog-to-digital converter responsive to an output of said filter network for generating said output data stream; a digital-to-analog converter responsive to said output stream for generating a feedback signal; means for summing said analog signal and said feedback signal to generate said error signal; means responsive to said feedback signal for injecting a partial feedback signal into a first plurality of predetermined points in said filter network; a plurality of prefilters connected in parallel to said analog input, each of said prefilters generating a partial prefilter signal; and means for applying a partial prefilter signal into a second plurality of predetermined points in said filter network.

Claim 27

A sigma delta modulator for generating an output digital data stream from an analog signal, said modulator comprising: a filter network for receiving and processing an error signal; an analog-to-digital converter responsive to an output of said filter network for generating said output data stream; a digital-to-analog converter responsive to said output stream for generating a feedback signal; means for summing said analog signal and said feedback signal to generate said error signal; means responsive to said feedback signal for injecting a partial feedback signal into a first plurality of predetermined points in said filter network; a plurality of prefilters connected in parallel to said analog input, each of said prefilters generating a partial prefilter signal; and means for applying a partial prefilter signal into a second plurality of predetermined points in said filter network.

Claim 28

A sigma delta modulator for generating an output digital data stream from an analog signal, said modulator comprising: a plurality of filter modules for receiving and processing an error signal; means connecting said filter modules in series; means for injecting a signal between each pair of filter modules; at least one resonator feedback network connecting an output of a resonator pair of filter modules to an input of said resonator pair of filter modules to form a resonator; an analog-to-digital converter responsive to an output of said plurality of filter modules for generating said output data stream; a digital-to-analog converter responsive to said output stream for generating a feedback signal; means for summing said analog signal and said feedback signal to generate said error signal; and means responsive to said feedback signal for applying a partial feedback signal to each of said injecting means and to said summing means.

Claim 29

A sigma delta modulator for generating an output digital data stream from an analog signal, said modulator comprising: a plurality of filter modules for receiving and processing an error signal; means connecting said filter modules in series; means for injecting a signal between each pair of filter modules; at least one resonator feedback network connecting an output of a resonator pair of filter modules to an input of said resonator pair of filter modules to form a resonator; an analog-to-digital converter responsive to an output of said plurality of filter modules for generating said output data stream; a digital-to-analog converter responsive to said output stream for generating a feedback signal; means for summing said analog signal and said feedback signal to generate said error signal; and means responsive to said feedback signal for applying a partial feedback signal to each of said injecting means and to said summing means.

Claim 30

A sigma delta modulator according to claim 24 wherein said injecting means comprises a plurality of summing junctions and said resonator feedback network is connected between an output of a resonator pair of filter modules to one of said plurality of summing junctions at said input of said resonator pair of filter modules.

Claim 31

A sigma delta modulator according to claim 24 wherein each of said filter modules comprises an integrator.

Claim 32

A sigma delta modulator for generating an output digital data stream from an analog signal at an analog input, said modulator comprising: a first summing junction responsive to said analog signal for generating a first error signal; a first integrator responsive to said error signal for generating a first integrated error signal; a second summing junction responsive to said first integrated error signal for generating a second error signal; a second integrator responsive to said second error signal for generating a second integrated error signal; a third summing junction responsive to said second integrated error signal for generating a third error signal; a third integrator responsive to said third error signal and having an output; a resonator feedback network connected between said third integrator output and said second summing junction to form a resonator; means responsive to said third integrator output for generating an output error signal; a comparator responsive to said output error signal for generating said output data stream; a selection switch responsive to said output stream for selecting one of two reference voltages as a feedback signal; a first feedback circuit responsive to said feedback signal for generating a first partial feedback signal; means for applying said first partial feedback signal to said second summing junction to be summed with said integrated error signal to generate said second error signal; a second feedback circuit responsive to said first partial feedback signal for generating a second partial feedback signal; and means for applying said second partial feedback signal to said first summing junction to be summed with said analog signal to generate said first error signal.

Claim 33

A sigma delta modulator for generating an output digital data stream from an analog signal at an analog input, said modulator comprising: a first summing junction responsive to said analog signal for generating a first error signal; a first integrator responsive to said error signal for generating a first integrated error signal; a second summing junction responsive to said first integrated error signal for generating a second error signal; a second integrator responsive to said second error signal for generating a second integrated error signal; a third summing junction responsive to said second integrated error signal for generating a third error signal; a third integrator responsive to said third error signal and having an output; a resonator feedback network connected between said third integrator output and said second summing junction to form a resonator; means responsive to said third integrator output for generating an output error signal; a comparator responsive to said output error signal for generating said output data stream; a selection switch responsive to said output stream for selecting one of two reference voltages as a feedback signal; a first feedback circuit responsive to said feedback signal for generating a first partial feedback signal; means for applying said first partial feedback signal to said second summing junction to be summed with said integrated error signal to generate said second error signal; a second feedback circuit responsive to said first partial feedback signal for generating a second partial feedback signal; and means for applying said second partial feedback signal to said first summing junction to be summed with said analog signal to generate said first error signal.