Radio frequency bandpass delta-sigma analog-to-digital converters and related methods

Patent metadata

Field	Value
Publication number	US-10862504-B2
Application number	US-201916533497-A
Country	US
Kind code	B2
Filing date	Aug 6, 2019
Priority date	Aug 29, 2018
Publication date	Dec 8, 2020
Grant date	Dec 8, 2020

Abstract

Radio-frequency (RF) receivers having bandpass sigma-delta analog sigma analog-to-digital converters (ADC) designed to digitize signals in the RF domain are described. Such bandpass ADCs utilize one or more of the following techniques to enhance noise immunity and reduce power consumption: generation of in-phase (I) and quadrature (Q) paths in the digital domain, nth order resonant bandpass filtering with n>1, and signal sub-sampling in an ith Nyquist zone with i>1. Compared to RF receivers in which the I and Q paths are generated in the analog domain, these RF receivers exhibit higher IRRs because they are not susceptible to in-phase/quadrature (IQ) mismatch. Using nth order resonant bandpass filtering with n>1 attenuates unwanted image tones. The bandpass ADC-based RF receivers described herein exhibit enhanced immunity to noise, achieving for example image rejection ratios (IRR) in excess of 95 dB.

First claim

What is claimed is:

1. A method for processing a radio-frequency (RF) signal, the method comprising;
amplifying the RF signal;
digitizing, with a delta-sigma analog-to-digital converter (ADC), the RF signal in an RF domain, wherein the digitizing comprises:
filtering the RF signal with an n th order resonant bandpass filter, where n>1;
sampling the RF signal in an i th Nyquist zone, where i>1;
producing an in-phase (I) signal and a quadrature (Q) signal digitally; and
converting an output of a quantizer with a digital-to-analog converter (DAC),
wherein converting the output of the quantizer with the DAC comprises up-converting, by the DAC, a frequency of the output of the quantizer.

2. The method of claim 1 , wherein amplifying the RF signal comprises amplifying the RF signal with a low noise amplifier directly connected to the ADC.

3. The method of claim 1 , wherein filtering the RF signal with the n th order resonant bandpass filter comprises filtering the RF signal with a first filter and with a second filter downstream from the first filter, wherein the first filter has a greater dynamic range than the second filter.

4. The method of claim 1 , wherein up-converting the frequency of the output of the quantizer comprises up-converting the frequency from 2-4 GHz to 6-12 GHz.

5. A method for processing a radio-frequency (RF) signal, the method comprising;
amplifying the RF signal;
digitizing, with a delta-sigma analog-to-digital converter (ADC), the RF signal in an RF domain, wherein the digitizing comprises:
filtering the RF signal with an n th order resonant bandpass filter, where n>1;
sampling the RF signal in an i th Nyquist zone, where i>1; and
producing an in-phase (I) signal and a quadrature (Q) signal digitally,

wherein filtering the RF signal with the n th order resonant bandpass filter comprises:
filtering the RF signal with a plurality of filters comprising a first filter and a second filter;
providing an output of a quantizer of the ADC to a first DAC and to a second DAC;
upconverting, by the first DAC, a frequency of the output of the quantizer; and
providing an output of the first DAC to an input of the first filter and providing an output of the second DAC to an input of the second filter.

6. A radio-frequency (RF) receiver comprising:
a low noise amplifier (LNA); and
an RF domain delta-sigma analog-to-digital converter (ADC) comprising:
an n th order resonant bandpass filter, where n>1;
a quantizer; and
circuitry configured to:
sample a RF signal in an i th Nyquist zone, where i>1; and
produce an in-phase (I) signal and a quadrature (Q) signal digitally,

wherein the ADC further comprises a digital-to-analog converter (DAC) connected to an output of the quantizer,
wherein the DAC is configured to up-convert a frequency of the output of the quantizer.

7. The RF receiver of claim 6 , wherein the DAC is configured to up-convert the frequency from 2-4 GHz to 6-12 GHz.

8. The RF receiver of claim 6 , wherein the LNA is directly connected to the ADC.

9. The RF receiver of claim 6 , wherein the RF receiver lacks local oscillators.

10. A radio-frequency (RF) receiver comprising:
an analog-to-digital converter (ADC) configured to digitize an RF signal in an RF domain at least in part by:
filtering the RF signal with an n th order resonant bandpass filter, where n>1;
sampling the RF signal in an i th Nyquist zone, where i>1; and
producing an in-phase (I) signal and a quadrature (Q) signal digitally,

wherein the ADC is further configured to convert an output of a quantizer with a digital-to-analog converter (DAC),
wherein the ADC is configured to convert the output of the quantizer with the DAC at least in part by up-converting a frequency of the output of the quantizer.

11. The RF receiver of claim 10 , wherein up-converting the frequency of the output of the quantizer comprises up-converting the frequency from 2-4 GHz to 6-12 GHz.

12. The RF receiver of claim 10 , wherein filtering the RF signal with the n th order resonant bandpass filter comprises:
filtering the RF signal with a plurality of filters comprising a first filter and a second filter;
providing an output of a quantizer to a first DAC and to a second DAC; and
providing an output of the first DAC to an input of the first filter and providing an output of the second DAC to an input of the second filter.

13. A radio-frequency (RF) receiver comprising:
a low noise amplifier (LNA); and
an RF domain delta-sigma analog-to-digital converter (ADC) comprising:
an n th order resonant bandpass filter, where n>1;
a quantizer; and
circuitry configured to:
sample a RF signal in an i th Nyquist zone, where i>1; and
produce an in-phase (I) signal and a quadrature (Q) signal digitally,

wherein the n th order resonant bandpass filter comprises:
a plurality of filters comprising a first filter and a second filter;
a plurality of DACs comprising a first DAC and a second DAC,
wherein the first and second DACs are connected to an output of the quantizer, the first DAC has an output connected to an input of the first filter and the second DAC has an output connected to an input of the second filter,
wherein the first DAC is configured to up-convert a frequency of the output of the quantizer.

14. The RF receiver of claim 13 , wherein the second filter is downstream from the first filter, wherein the first filter has a greater dynamic range than the second filter.

Assignees

• Mediatek Singapore Pte Ltd

Inventors

• Mitteregger Gerhard

Classifications

• H03M3/464

  Details of the digital/analogue conversion in the feedback path · CPC title

• H03M3/40

  Arrangements for handling quadrature signals, e.g. complex modulators · CPC title

• H03M3/494

  Sampling or signal conditioning arrangements specially adapted for delta-sigma type analogue/digital conversion systems · CPC title

• H03M3/454

  with distributed feedback, i.e. with feedback paths from the quantiser output to more than one filter stage · CPC title

• H03M3/32 Primary

  with special provisions or arrangements for power saving, e.g. by allowing a sleep mode, using lower supply voltage for downstream stages, using multiple clock domains, by selectively turning on stages when needed · CPC title