Analog/digital converter and milimeter wave radar system

Patent metadata

Field	Value
Publication number	US-10707894-B2
Application number	US-201815900598-A
Country	US
Kind code	B2
Filing date	Feb 20, 2018
Priority date	Apr 18, 2017
Publication date	Jul 7, 2020
Grant date	Jul 7, 2020

Abstract

A modulator includes an analog integrator including an analog circuit and a quantizer quantizing its output signal. An external input signal is input thereto. A modulator is coupled to the latter stage of the modulator, and includes a quantizer. A probe signal generation circuit injects a probe signal to the modulator. An adaptive filter searches for a transfer function of the modulator by observing an output signal of the quantizer in accordance with a probe signal. Another adaptive filter searches for a transfer function of the modulator by observing an output signal of the quantizer in accordance with the probe signal. A noise cancel circuit cancels a quantization error generated by the quantizer using search results of the adaptive filters.

First claim

What is claimed is:

1. A MASH (Multi stAge Noise SHaping) type and sigma-delta type analog/digital converter comprising:
a first modulator which includes a first analog integrator including an analog circuit and a first quantizer quantizing an output signal of the first analog integrator, and to which an external input signal as an analog signal is input;
a second modulator which is coupled to a latter stage of the first modulator and includes a second quantizer;
a probe signal generation circuit which injects a probe signal to the first modulator;
a first adaptive filter which searches for a transfer function of the first modulator by observing an output signal of the first quantizer in accordance with the probe signal;
a second adaptive filter which searches for a transfer function of the second modulator by observing an output signal of the second quantizer in accordance with the probe signal; and
a noise cancel circuit which cancels an quantization error generated by the first quantizer using a search result of the first adaptive filter and a search result of the second adaptive filter.

2. The analog/digital converter according to claim 1 ,
wherein the probe signal is a pseudo random signal.

3. The analog/digital converter according to claim 2 ,
wherein the probe signal is a 1-bit pseudo random signal.

4. The analog/digital converter according to claim 1 ,
wherein the probe signal is an analog signal, and injected to an input signal of the first quantizer through a third analog adder/subtracter.

5. The analog/digital converter according to claim 1 ,
wherein the probe signal is a digital signal, and injected to an output signal of the first quantizer through a third digital adder/subtracter.

6. The analog/digital converter according to claim 1 ,
wherein the noise cancel circuit includes:
a first noise cancel filter which is a digital filter to which the output signal of the first quantizer is input, and includes a tap coefficient based on the search result of the second adaptive filter,
a second noise cancel filter which is a digital filter to which the output signal of the second quantizer is input, and includes a tap coefficient based on the search result of the first adaptive filter, and
a first digital adder/subtracter which calculates a difference between an output signal of the first noise cancel filter and an output signal of the second noise cancel filter.

7. The analog/digital converter according to claim 1 ,
wherein the first adaptive filter searches for its own tap coefficient using an LMS (Least Mean Square) algorithm, based on a first error signal as an error between the output signal of the first quantizer in accordance with the probe signal and an output signal of the first adaptive filter, and
wherein the second adaptive filter searches for its own tap coefficient using the LMS algorithm, based on a second error signal as an error between the output signal of the second quantizer in accordance with the probe signal and an output signal of the second adaptive filter.

8. The analog/digital converter according to claim 7 ,
wherein each of the first adaptive filter and the second adaptive filter includes a plurality of tap circuits and a digital adder which adds an output signal of each of the tap circuits,
wherein each of the tap circuits includes
a first digital multiplier which multiplies a corresponding error signal of the first error signal and the second error signal by a delay probe signal,
a digital integrator which integrates a value obtained by multiplying a multiplication result of the first digital multiplier by a predetermined step coefficient, and
a second digital multiplier which multiplies the delay probe signal by an integration result of the digital integrator, and outputs this multiplication result to the digital adder, and

wherein the delay probe signal differs between the tap circuits, and is obtained by delaying the probe signal by degrees different between the tap circuits.

9. The analog/digital converter according to claim 1 ,
wherein the first analog integrator includes a circuit parameter which can be variably set, and
wherein the analog/digital converter further includes an adjustment circuit which adjusts the circuit parameter of the first analog integrator based on the search result of the first adaptive filter.

10. The analog digital converter according to claim 6 , further comprising
a frequency characteristic correction circuit which corrects a frequency characteristic of the analog/digital converter, by causing the search result of the first adaptive filter and the search result of the second adaptive filter to be reflected to an output signal of the first digital adder/subtracter.

11. A MASH (Multi stAge Noise SHaping) type and sigma-delta type analog/digital converter comprising:
a first modulator to which an external input signal as an analog signal is input, and which includes a first quantizer;
a second modulator which is coupled to a latter stage of the first modulator and includes a second quantizer;
a probe signal generation circuit which generates a first probe signal and injects the first probe signal to the first modulator;
a first adaptive filter which searches for a transfer function of the first modulator by observing an output signal of the first quantizer in accordance with the first probe signal;
a second adaptive filter which searches for a transfer function of the second modulator by observing an output signal of the second quantizer; and p 1 a noise cancel circuit which cancels an quantization error generated by the first quantizer using a search result of the first adaptive filter and a search result of the second adaptive filter,
wherein the first modulator includes
a first analog integrator which includes an analog circuit,
the first quantizer which quantizes an output signal of the first analog integrator,
a first digital/analog converter circuit which converts an output signal of the first quantizer into an analog signal, and
a first analog adder/subtracter which outputs a differential signal between the external input signal and an output signal of the first digital/analog converter circuit.

12. The analog/digital converter according to claim 11 ,
wherein the first probe signal is injected to an input signal or output signal of the first quantizer.

13. The analog/digital converter according to claim 11 ,
wherein the first probe signal is injected to the first analog adder/subtracter.

14. The analog/digital converter according to claim 11 ,
wherein the second modulator includes
a second analog integrator which includes an analog circuit,
the second quantizer which quantizes an output signal of the second analog integrator,
a second digital/analog converter circuit which converts an output signal of the second quantizer into an analog signal, and
a second analog adder/subtracter which outputs a differential signal between a first signal including a component of the quantization error as a signal from the first modulator and an output signal of the second digital/analog converter circuit, to the second analog integrator.

15. The analog/digital converter according to claim 14 ,
wherein the first probe signal is injected to the first analog adder/subtracter and the second analog adder/subtracter.

16. The analog/digital converter according to claim 14 ,
wherein the probe signal generation circuit further generates a second probe signal, and injects the second probe signal to the second analog adder/subtracter, and
wherein the second adaptive filter sear

Assignees

• Renesas Electronics Corp

Inventors

• Oshima Takashi
• Matsui Tetsuo
• Fukazawa Mitsuya
• Yano Tomohiko

Classifications

• H03M3/414 Primary

  having multiple quantisers arranged in cascaded loops, each of the second and further loops processing the quantisation error of the loop preceding it, i.e. multiple stage noise shaping [MASH] type · CPC title

• H03M3/38 Primary

  Calibration · CPC title

• H03M3/388

  by storing corrected or correction values in one or more digital look-up tables · CPC title

• H03M3/458

  Analogue/digital converters using delta-sigma modulation as an intermediate step · CPC title

• G01S7/354

  Extracting wanted echo-signals (Doppler systems G01S13/50) · CPC title