Multichannel transmit and/or receive system comprising at least N parallel processing channels and method for decorrelating quantization noise in such a system

Patent metadata

Field	Value
Publication number	US-12388463-B2
Application number	US-202318237842-A
Country	US
Kind code	B2
Filing date	Aug 24, 2023
Priority date	Aug 30, 2022
Publication date	Aug 12, 2025
Grant date	Aug 12, 2025

Abstract

A multichannel transmit and/or receive system, each channel includes a DAC and a sigma-delta modulator the transfer function of which is expressed thus:

OUT( z )=IN( z )· FTS ( z )+ Q ( z )· FTB ( z ),

where OUT is the output signal of the sigma-delta modulator, IN is the input signal of the sigma-delta modulator, FTS is the transfer function of the input signal, Q is the quantization noise and FTB is the transfer function of the quantization noise, the second terms of the transfer function of the sigma-delta modulator only being distinct from one another for two channels Vi, Vj, in order to decorrelate the quantization noise of distinct channels, the first term of said transfer function for channel Vi being equal to the first term of said transfer function for channel Vj.

First claim

The invention claimed is:

1. A multichannel transmit and/or receive system comprising at least N parallel processing channels (V 0 , V 1 ), N≥2, each coupled to one respective transducer and each comprising a converter block comprising an ADC or DAC converter and a sigma-delta modulator,
the transfer function of the sigma-delta modulator of each channel Vi, i=1 to N, being defined as a sum of two terms comprising a first term IN(z)·FTS(z) relating to the signal and a second term Q(z)·FTB(z) relating to the quantization noise introduced by the sigma-delta modulator and being expressed thus:
OUT( z )=IN( z )· FTS ( z )+ Q ( z )· FTB ( z ),

where OUT is the output signal of the sigma-delta modulator, IN is the input signal of the sigma-delta modulator, FTS is the transfer function of the input signal, Q is the quantization noise and FTB is the transfer function of the quantization noise,
the transfer function of the sigma-delta modulator of a channel Vi being distinct from the transfer function of the sigma-delta modulator of a channel Vj, i and j being distinct integers comprised between 1 and N, in order to decorrelate the quantization noise of distinct channels,
said multichannel system wherein, for distinct channels Vi, Vj, the second terms of the transfer function of the sigma-delta modulator only are distinct, the first term of said transfer function for channel Vi being equal to that for channel Vj.

2. The multichannel transmit and/or receive system according to claim 1 , wherein the sigma-delta modulator on each of the channels Vi, Vj (V 0 , V 1 ) comprises a 1-bit hysteresis quantizer, and the hysteresis cycle is different between the channels Vi, Vj in amplitude and/or temporally.

3. The multichannel transmit and/or receive system according to claim 1 , wherein the sigma-delta modulator on each of the channels Vi, Vj comprises a multi-bit quantizer;
and the value of the input signal corresponding to the switch between two quantization levels on channel Vi is set so as to be distinct from the value of the input signal corresponding to the switch between the same two quantization levels on channel Vj.

4. The multichannel transmit and/or receive system according to claim 3 , comprising, on each of the channels Vi, Vj, at least said sigma-delta modulator with multi-bit quantizer and an additional sigma-delta modulator, the output of one of said modulators being input into the other of said modulators, said other sigma-delta modulator on the channel Vi being identical to said other sigma-delta modulator on the channel Vj.

5. The multichannel transmit and/or receive system according to claim 1 , wherein, on each of the channels Vi, Vj, the sigma-delta modulator is a sigma-delta modulator ( 12 ″) of cascaded architecture comprising at least two stages, the first stage comprising a first delta-sigma modulator especially comprising a quantizer and the second stage comprising at least a second sigma-delta modulator;
the second stage being configured to receive as input the output of the quantizer of the first modulator and the input of the quantizer of the first modulator, to digitize, via the second comparator, a signal representative of the quantization noise of the first modulator and to shape it;
the difference between a signal proportional to the output of the quantizer of the first modulator and a signal proportional to the input of the quantizer of the first modulator being input into the second modulator;
the output of the second stage then being subtracted from the output of the first modulator to deliver a signal devoid of at least some of the quantization noise of the first stage,
wherein the second stage of channel Vi is different from the second stage on channel Vj so as to differentiate between the quantization noise of the second modulator of channels Vi, Vj.

6. The multichannel transmit and/or receive system according to claim 5 , wherein the second stage comprises multipliers, each multiplier multiplying its input by a respective associated coefficient, wherein, considering at least one of said multipliers, the coefficient associated with it on channel Vi has a value different from the coefficient associated with it on channel Vj.

7. The multichannel transmit and/or receive system according to claim 5 , wherein a delay-generating block is placed, in the second stage, between the output of the first modulator and the input of the second modulator, said delay-generating block being configured to apply a delay to the signal delivered by said output, the delay on channel Vi being set to a value different from the value of the delay on channel Vj.

8. A method for decorrelating quantization noise in a multichannel transmit and/or receive system comprising at least N parallel processing channels, N≥2, each coupled to one respective transducer and each comprising a converter block comprising an ADC or DAC converter and a sigma-delta modulator,
the transfer function of the sigma-delta modulator of each channel Vi, i=1 to N, being defined as a sum of two terms comprising a first term IN(z)·FTS(z) relating to the signal and a second term Q(z)·FTB(z) relating to the quantization noise introduced by the sigma-delta modulator ( 12 ) and being expressed as follows:
OUT( z )=IN( z )· FTS ( z )+ Q ( z )· FTB ( z ),

where OUT is the output signal of the sigma-delta modulator, IN is the input signal of the sigma-delta modulator, FTS is the transfer function of the input signal, Q is the quantization noise and FTB is the transfer function of the quantization noise,
in which method the operation of the sigma-delta modulator of channel Vi is configured with respect to the operation of the sigma-delta modulator of channel Vj to decorrelate the quantization noise generated by the channels,
the transfer function of the sigma-delta modulator of a channel Vi being distinct from the transfer function of the sigma-delta modulator of a channel Vj, i and j being distinct integers comprised between 1 and N, in order to decorrelate the quantization noise of distinct channels,
said method wherein, for distinct channels Vi, Vj, the second terms of the transfer function of the sigma-delta modulator only are distinct, the first term of said transfer function for channel Vi being equal to that for channel Vj.

9. The method for decorrelating quantization noise according to claim 8 , wherein the sigma-delta modulator on each of the channels Vi, Vj comprises a 1-bit hysteresis quantizer, and the hysteresis cycle is different between the channels Vi, Vj in amplitude and/or temporally.

10. The method according to claim 8 , wherein the sigma-delta modulator on each of the channels Vi, Vj comprises a multibit quantizer, and the value of the input signal corresponding to the switch between two quantization levels on channel Vi is set so as to be distinct from the value of the input signal corresponding to the switch between the same two quantization levels on channel Vj.

Assignees

• Commissariat Energie Atomique

Inventors

• Morche Dominique
• Verdant Arnaud

Classifications

• H03M3/424

  the quantiser being a multiple bit one · CPC title

• H03M1/0854

  of quantisation noise · CPC title

• H03M3/50

  Digital/analogue converters using delta-sigma modulation as an intermediate step (digital delta-sigma modulators per se H03M7/3004) · CPC title

• H03M3/414

  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

• H04B7/0617

  for beam forming · CPC title