Low noise transmission of output data from a delta-sigma modulator
AssigneeCrystal Semiconductor Corporation
InventorsEric J. Swanson, Charles D. Thompson
Life of this patent
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Abstract
The output gates of a delta-sigma modulator can generate i(t) transient signal in the power supply lines of a delta-sigma modulator. These i(t) spikes, which would otherwise produce non-linearities which can be coupled into the frequency band of interest of the modulator, are made to be linear by using return-to-zero data encoding and by providing multi-bit outputs to the delta-sigma modulator in which the output states all have equal numbers of logic ones at the output lines for each of the output states.
Claims14
A delta-sigma modulator which receives an analog input signal and provides a digital output of serial data in an output stage of the delta-sigma modulator wherein said digital output is in the form of a code which, for each sampling period, is output transient noise-invariant as compared to any other sampling period, and wherein said output transient noise produced by each bit of a first logic state of said digital output is independent of any previous of said digital outputs and wherein said output transient signals produced by each bit of a second logic state of said digital output is independent of any previous of said digital outputs.
A delta-sigma modulator which receives an analog input signal and provides N digital output signals at N digital output terminals wherein said N digital output signals during each output bit period encodes into one of K digital logic states wherein K is the number of allowed permutations of said N output signals and is less than 2.sup.N and wherein the sum of the number of said N digital output terminals which produce a transient signal of a first polarity is the same for each of said K digital logic states.
A delta-sigma modulator which receives an analog input signal and provides a digital output of serial data in an output stage of the delta-sigma modulator characterized in that said digital output is in the form of return-to-zero encoded data and wherein said digital output consists of K digital states presented at N digital output terminals, wherein the sum of the number of said N digital output terminals having a first logic state is the same for each of said K digital states.
A delta-sigma analog-to-digital convertor having a delta-sigma modulator which receives an analog input signal and provides a digital output of modulated data to a digital filter which filters said digital output to provide N filtered digital output signals at N digital output terminals in an output stage of said digital filter wherein said N filtered digital output signals during each output bit period encodes into one of K digital logic states wherein K is the number of allowed permutations of said N output signals and is less than 2.sup.N and, wherein the sum of the number of said N digital output terminals which produce a transient signal of a first polarity is the same for each of said K digital logic states.
A delta-sigma analog-to-digital convertor having a delta-sigma modulator which receives an analog input signal and provides a digital output of serial data to a digital filter which filters said digital output to provide a filtered digital output in an output stage of said digital filter characterized in that said filtered digital output is in the form of return-to-zero encoded data.
Dependencies are inferred from the claim text.