Back to results
US 6,147,634 AGranted
Method and apparatus for digital to analog conversion with reduced noise
AssigneeSigmatel, Inc.
InventorsGiri N Rangan, Mathew A Rybicki
Life of this patent
Estimating the term…
Abstract
A method and apparatus for digital to analog signal conversions with reduced noise include processing that begins by receiving a digital signal and filtering the digital signal to produce a filtered digital signal. The filtering is tuned to attenuate components of the digital signal having frequencies near one-half the sampling rate frequency and to pass other components of the digital signal having frequencies away from one-half the sampling rate frequency. The filtered signals are then converted to analog signals based on a clock signal having a sampling rate frequency and a voltage reference.
Claims11
A digital to analog converter comprises:
- a filter operably coupled to receive digital input signals and to output filtered digital signals, wherein the filter attenuates components of the digital input signals having frequencies near half a sampling frequency and passes, substantially unattenuated, other components of the digital input signals having frequencies away from half the sampling frequency;
- and
- digital to analog converter module operably coupled to receive the filtered digital signals, wherein the digital to analog converter module, based on a clock signal having the sampling frequency and a voltage reference, generates analog signals from the filtered digital signals, such that, when the digital input signals are substantially comprised of components near half of the sampling frequency, the analog signals have minimal noise components having frequencies near half the sampling frequency.
A sigma-delta modulator comprises:
- a first order stage operably coupled to receive an analog input signal and a first analog feedback signal and to produce therefrom an integrated analog signal;
- quantizer operably coupled to receive a representation of the integrated analog signal and to produce therefrom a quantized digital signal;
- and
- digital to analog converter operably coupled to receive the quantized digital signal and to produce therefrom the first analog feedback signal, wherein the digital to analog converter includes:
- a filter operably coupled to receive the quantized digital signal and to output a filtered digital signal, wherein the filter attenuates components of the quantized digital signal having frequencies near half a sampling frequency and passes, substantially unattenuated, other components of the quantized digital signal having frequencies away from half the sampling frequency;
- and
- digital to analog converter module operably coupled to receive the filtered digital signal, wherein the digital to analog converter module, based a clock signal having the sampling frequency and a voltage reference, generates the first analog feedback signal from the filtered digital signal.
4 more elements
A method for converting a digital signal into an analog signal, the method comprises the steps of:
- receiving the digital signal;
- filtering the digital signal to produce a filtered digital signal, wherein the filtering attenuates components of the digital signal having frequencies near half a sampling frequency to produce an attenuated digital signal and passes, substantially unattenuated, other components of the digital signal having frequencies away from half the sampling frequency;
- and
- converting the filtered digital signal, based a clock signal having the sampling frequency and a voltage reference, into the analog signal, such that, when the digital signal is substantially comprised of components near half of the sampling frequency, the analog signal has minimal noise components having frequencies near half the sampling frequency.
1 more element
A digital to analog converting module comprises:
- a processing module;
- and
- memory operably coupled to the processing module, wherein the memory stores operational instructions that cause the processing module to receive a digital signal, filter the digital signal to produce a filtered digital signal, wherein the filtering attenuates components of the digital signal having frequencies near half a sampling frequency to produce an attenuated digital signal and passes, substantially unattenuated, other components of the digital signal having frequencies away from half the sampling frequency;
- and convert the filtered digital signal, based a clock signal having the sampling frequency and a voltage reference, into the analog signal, such that, when the digital signal is substantially comprised of components near half of the sampling frequency, the analog signal has minimal noise components having frequencies near half the sampling frequency.
1 more element
Dependencies are inferred from the claim text.