# US 8,570,200 B2 · Continuous-time oversampled converter having enhanced immunity to noise > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,570,200 B2 - Document ID: US8570200B2 - Status: Granted - Kind: B2 - Application number: 13/337,143 - Filed: 2011-12-25 - Published: 2012-07-26 - Granted: 2013-10-29 - Earliest claimed: 2011-01-20 - Assignees: MediaTek Singapore Pte. Ltd. - Applicants: Michael A. Ashburn, Jr.; Jeffrey Carl Gealow; Paul F. Ferguson, Jr. - Inventors: Michael A. Ashburn, Jr.; Jeffrey Carl Gealow; Paul F. Ferguson, Jr. - Web page: https://patentgrep.com/patent/US8570200B2 ## CPC - H03M 3/344: {by filtering other than the noise-shaping inherent to delta-sigma modulators, e.g. anti-aliasing} - H03M 3/50: {Digital/analogue converters using delta-sigma modulation as an intermediate step (digital delta-sigma modulators per se H03M7/3004)} - H03M 7/304: {with distributed feedback, i.e. with feedback paths from the quantiser output to more than one filter stage} - H03M: CODING; DECODING; CODE CONVERSION IN GENERAL (using fluidic means F15C4/00; optical analogue/digital converters G02F7/00; coding, decoding or code conversion, specially adapted for particular applications, see the relevant subclasses, e.g. G01D, G01R, G06F, G06T, G09G, G10L, G11B, G11C, H04B, H04L, H04M, H04N; ciphering or deciphering for cryptography or other purposes involving the need for secrecy G09C) ## Abstract An apparatus includes a clock source and an oversampled continuous-time digital-to-analog converter. Noise signal is added to the clock signal as the clock signal is generated and/or routed. The oversampled continuous-time digital-to-analog converter includes a sigma-delta modulator to perform noise shaping on input data samples and provide intermediate data samples; a filter to filter the intermediate data samples and generate filtered samples, the filter having a transfer function that has a stop band at a frequency range that includes the frequency of the noise signal or a component of the noise signal; and a continuous-time digital-to-analog converter to convert the filtered samples to an output analog signal. ## Claims ### Claim 1 An apparatus comprising: a clock source to generate a clock signal in which a noise signal is added to the clock signal as the clock signal is generated and/or routed; an oversampled continuous-time digital-to-analog converter comprising: a sigma-delta modulator to perform noise shaping on input digital data samples and provide intermediate data samples; a filter to filter the intermediate data samples and generate filtered samples, the filter having a transfer function that has a stop band at a frequency range that includes the frequency of the noise signal or a component of the noise signal; and a continuous-time digital-to-analog converter to convert the filtered samples to an output analog signal; wherein the clock signal or a signal derived from the clock signal is used by one or more components of the oversampled continuous-time digital-to-analog converter. ### Claim 2 (depends on 1) The apparatus of claim 1 in which the filter transfer function has a notch at a frequency that matches the frequency of the noise signal or a component of the noise signal. ### Claim 3 (depends on 2) The apparatus of claim 2 in which the clock source comprises a phase-locked loop or a delay-locked loop having a reference clock operating at a reference clock frequency, and the notch in the filter transfer function is set at a frequency that matches the reference clock frequency or a harmonic of the reference clock frequency. ### Claim 4 (depends on 1) The apparatus of claim 1 in which the input digital data samples are associated with an analog signal, having component frequencies within a frequency band of interest, the sigma-delta modulator performs noise shaping on the input data samples to reduce quantization noise of the filtered samples within the frequency band of interest and place some of the quantization noise outside of the frequency band of interest, and the stop band is outside of the frequency band of interest. ### Claim 5 An apparatus comprising: a clock source to generate a clock signal in which a noise signal is added to the clock signal as the clock signal is generated and/or routed; an oversampled continuous-time analog-to-digital converter to convert an input analog signal to an output digital signal, the oversampled continuous-time analog-to-digital converter comprising: a quantizer to quantize a first intermediate signal and generate the output digital signal; a first filter to filter the output digital signal and generate a first filtered digital signal, the first filter having a transfer function that has a stop band at a frequency range that includes the frequency of the noise signal or a component of the noise signal; a first feedback continuous-time digital-to-analog converter to convert the first filtered digital signal to a first analog representation of the first filtered digital signal; and a first circuit to generate a second intermediate signal representing a difference between the input analog signal and the first analog representation of the first filtered digital signal; wherein the clock signal or a signal derived from the clock signal is used by one or more components of the oversampled continuous-time analog-to-digital converter. ### Claim 6 (depends on 5) The apparatus of claim 5 in which the first filter transfer function has a notch at a frequency that matches the frequency of the noise signal or a component of the noise signal. ### Claim 7 (depends on 6) The apparatus of claim 6 in which the clock source comprises a phase-locked loop or a delay-locked loop having a reference clock operating at a reference clock frequency, and the notch in the first filter transfer function has a frequency that matches the reference clock frequency or a harmonic of the reference clock frequency. ### Claim 8 (depends on 5) The apparatus of claim 5 in which the input analog signal has component frequencies within a frequency band of interest, the quantizer, the first filter, the feedback digital-to-analog converter, and the first circuit form a sigma-delta modulator that performs noise shaping to reduce quantization noise of the output digital signal within the frequency band of interest and place some of the quantization noise outside of the frequency band of interest, and the stop band is outside of the frequency band of interest. ### Claim 9 (depends on 5) The apparatus of claim 5, further comprising: a second filter to filter the output digital signal and generate a second filtered digital signal; a second feedback continuous-time digital-to-analog converter to convert the second filtered digital signal to a second analog representation of the second filtered digital signal; and a second circuit to generate a third intermediate signal representing a difference between a processed version of the second intermediate signal and the second analog representation of the second filtered digital signal. ### Claim 10 An apparatus comprising: an oversampled continuous-time digital-to-analog converter comprising: a first filter to filter an oversampled digital signal and generate a filtered oversampled digital signal, the filter having a transfer function that has a stop band at a frequency range that includes the frequency of a noise signal, the stop band being outside of a frequency band of interest; a continuous-time digital-to-analog converter to convert the filtered samples to a first analog signal; and a second filter to filter the first analog signal and generate an output analog signal, the second filter reducing components in the output analog signal having frequencies outside of the frequency band of interest. ### Claim 11 (depends on 10) The apparatus of claim 10, further comprising a clock source that generates a clock signal in which a phase noise peak is added to a noise level of the clock signal as the clock signal is generated and/or routed, wherein the first filter transfer function includes a notch that occurs at a frequency that matches the frequency of the phase noise peak. ### Claim 12 An apparatus comprising: an oversampled continuous-time analog-to-digital converter to convert an input analog signal to an output digital signal, the oversampled continuous-time analog-to-digital converter comprising: a quantizer to quantize a first intermediate signal and generate the output digital signal; a first filter to filter the output digital signal and generate a first filtered digital signal, the first filter having a transfer function having a stop band at a frequency range that includes the frequency of a noise signal; a first feedback continuous-time digital-to-analog converter to convert the first filtered digital signal to a first analog representation of the first filtered digital signal; and a first circuit to generate a second intermediate signal representing a difference between the input analog signal and the first analog representation of the first filtered digital signal. ### Claim 13 (depends on 12) The apparatus of claim 12, further comprising a clock source that generates a clock signal in which phase noise peaks are added to a noise level of the clock signal as the clock signal is generated and/or routed, wherein the first filter transfer function includes a notch that occurs at a frequency that matches at least one frequency of the noise peaks. ### Claim 14 (depends on 12) The apparatus of claim 12, further comprising: a second filter to filter the output digital signal and generate a second filtered digital signal, the second filter compensating for feedback delays produced by the first filter; and a second feedback continuous-time digital-to-analog converter to convert the second filtered digital signal to a third intermediate signal that is fed into a second feedback loop. ### Claim 15 An apparatus comprising: an oversampled continuous-time converter to convert an input signal into an output signal having a format that is different from the input signal, the continuous-time oversampled converter comprising: a filter to filter an oversampled digital signal and generate a filtered signal, the filter having a transfer function having a stop band at a frequency range that includes a frequency of a noise signal, the stop band being outside of a frequency band of interest; and a continuous-time digital-to-analog converter to convert the filtered signal to an analog signal. ### Claim 16 (depends on 15) The apparatus of claim 15 in which the oversampled continuous-time converter comprises an oversampled continuous-time digital-to-analog converter, the input signal comprises a digital signal, and the output signal comprises the analog signal or a filtered version of the analog signal. ### Claim 17 (depends on 15) The apparatus of claim 15 in which the oversampled continuous-time converter comprises an oversampled continuous-time analog-to-digital converter having a quantizer that generates the oversampled digital signal, and the analog signal from the continuous-time digital-to-analog converter is fed into a feedback loop. ### Claim 18 (depends on 15) The apparatus of claim 15 in which the filter transfer function has a notch at a frequency that matches the frequency of the noise signal or a component of the noise signal. ### Claim 19 A method of converting input digital data samples to an output analog signal, the method comprising: routing a clock signal having a noise signal; filtering oversampled digital data having components outside of a signal band of interest, by using a filter having a transfer function that has a stop band at a frequency that matches the frequency of the noise signal or a component of the noise signal, to generate filtered samples, the stop band being outside of the signal band of interest; and converting, using a continuous-time digital-to-analog converter, the filtered samples to an output analog signal. ### Claim 20 (depends on 19) The method of claim 19, further comprising: generating the clock signal using a phase-locked loop or a delay-locked loop having a reference clock operating at a reference clock frequency, and setting a notch in the filter transfer function at a frequency that matches the reference clock frequency or a harmonic of the reference clock frequency. ### Claim 21 (depends on 19) The method of claim 19 in which the filter transfer function has a notch at a frequency that matches the frequency of the noise signal or a component of the noise signal. ### Claim 22 A method of converting an input analog signal to an output digital signal, the method comprising: generating a clock signal; routing the clock signal, in which a noise signal is added to the clock signal as the clock signal is generated and/or routed; quantizing a first intermediate signal and generating an output digital signal; filtering the output digital signal and generating a filtered digital signal using a filter having a transfer function that has a stop band at a frequency range that includes the frequency of the noise signal or a component of the noise signal; converting, using a feedback continuous-time digital-to-analog converter, the filtered digital signal to an analog representation of the filtered digital signal; and generating a second intermediate signal representing a difference between an input analog signal and the analog representation of the filtered digital signal. ### Claim 23 (depends on 22) The method of claim 22, further comprising: generating the clock signal using a phase-locked loop or a delay-locked loop having a reference clock operating at a reference clock frequency, and setting a notch in the filter transfer function at a frequency that matches the reference clock frequency or a harmonic of the reference clock frequency. ### Claim 24 (depends on 22) The method of claim 22 in which the first filter transfer function has a notch at a frequency that matches the frequency of the noise signal or a component of the noise signal. ### Claim 25 An apparatus comprising: an oversampled continuous-time digital-to-analog converter to convert digital input data to analog output data, the oversampled continuous-time digital-to-analog converter comprising: a filter to filter oversampled data and generate filtered data, the filter having a transfer function that has a stop band at a frequency range that is outside a signal band of interest and includes the frequency of a noise component of a clock signal; and a continuous-time digital-to-analog converter to convert the filtered data to the analog output signal, the continuous-time digital-to-analog converter using the clock signal or another signal derived from the clock signal. ### Claim 26 (depends on 25) The apparatus of claim 25 in which the filter transfer function comprises a notch at a frequency that matches the frequency of the noise signal or a component of the noise signal. ### Claim 27 (depends on 25) The apparatus of claim 25 in which the frequency of the noise signal corresponds to the frequency of a reference clock signal or a harmonic frequency of the reference clock signal. ### Claim 28 An apparatus comprising: an oversampled continuous-time analog-to-digital converter to convert an analog input signal to a digital output signal, the oversampled continuous-time analog-to-digital converter comprising: a quantizer to quantize a first intermediate signal and generate the output digital signal; a filter to filter the output digital signal and generate a filtered digital signal, the filter having a transfer function that has a stop band at a frequency range that is outside a signal band of interest and includes the frequency of a noise component of a clock signal; a feedback continuous-time digital-to-analog converter to convert the filtered digital signal to an analog representation of the filtered digital signal, the continuous-time digital-to-analog converter using the clock signal or another signal derived from the clock signal; and a circuit to generate a second intermediate signal representing a difference between the analog input signal and the analog representation of the filtered digital signal. ### Claim 29 (depends on 28) The apparatus of claim 28 in which the filter transfer function comprises a notch at a frequency that matches the frequency of the noise signal or a component of the noise signal. ### Claim 30 (depends on 29) The apparatus of claim 29 in which the frequency of the noise signal corresponds to the frequency of a reference clock signal or a harmonic frequency of the reference clock signal.