Distortion compensation system and communication apparatus

Patent metadata

Field	Value
Publication number	US-9722819-B2
Application number	US-201415027534-A
Country	US
Kind code	B2
Filing date	Sep 22, 2014
Priority date	Oct 9, 2013
Publication date	Aug 1, 2017
Grant date	Aug 1, 2017

Abstract

A distortion compensation system includes a first communication node including a first reception unit including an equalizer configured by a first digital filter unit and a first transmission unit including an emphasis circuit configured by a second digital filter unit, and a second communication node including a second transmission unit transmitting a training pattern before receiving normal data from the first communication node. The equalizer converges a filter constant of the first digital filter unit so that an error of the received training pattern is converged. The first transmission unit performs a distortion compensation using the converged filter constant of the first digital filter unit as at least a part of a filter constant of the second digital filter unit of the emphasis circuit, and then transmits the data.

First claim

The invention claimed is:

1. A distortion compensation system comprising:
a first communication node including a first reception unit and a first transmission unit, the first reception unit including an equalizer and the equalizer including a first digital filter unit, and the first transmission unit including an emphasis circuit and the emphasis circuit including a second digital filter unit; and
a second communication node including a second transmission unit, and the second transmission unit transmitting through a first transmission line a training pattern determined in advance before receiving normal data from the first transmission unit of the first communication node through the first transmission line, wherein
the first communication node receives the training pattern transmitted from the second transmission unit of the second communication node over the first transmission line using the first reception unit,
the equalizer converges a filter constant of the first digital filter unit so that an error with respect to the training pattern to be received is converged,
the first transmission unit of the first communication node performs a distortion compensation on the normal data to be transmitted using the converged filter constant of the first digital filter unit as at least a part of a filter constant of the second digital filter unit of the emphasis circuit, and then transmits the normal data over the first transmission line,
wherein the first transmission line is an only transmission line between the first communication node and the second communication node, and
wherein the first transmission line includes a pair of differential communication cables.

2. The distortion compensation system according to claim 1 , wherein
the equalizer of the first reception unit is provided by a decision feedback equalizer (DFE) circuit,
the equalizer of the first reception unit includes, as the first digital filter unit, a first feedforward filter and a first feedback filter,
the equalizer of the first reception unit further includes a slicer,
the first feedforward filter performs a first digital filter processing on input data to the DFE circuit,
the first feedback filter performs a second digital filter processing on output data from the DFE circuit,
the slicer adds up an output of the first feedforward filter and an output of the first feedback filter and compares an addition result with an output of the DFE circuit in order to match the addition result with the output of the DFE circuit,
the emphasis circuit of the first transmission unit includes, as the second digital filter unit, a second feedforward filter and a second feedback filter,
the second feedforward filter performs a first digital filter processing on input data to the emphasis circuit,
the second feedback filter performs a second digital filter processing on output data from the emphasis circuit, and
the emphasis circuit of the first transmission unit adds up an output of the second feedforward filter and an output of the second feedback filter, and then outputs an addition result.

3. The distortion compensation system according to claim 1 , wherein
the equalizer of the first reception unit is provided by an adaptive linear equalizer,
the adaptive linear equalizer of the first reception unit includes, as the first digital filter unit, a first feedforward filter that performs a first digital filter processing on input data to the adaptive linear equalizer,
the adaptive linear equalizer of the first reception unit further includes a determiner that compares output data from the equalizer with an output of the first feedforward filter in order to match the output data from the equalizer with the output of the first feedforward filter,
the emphasis circuit of the first transmission unit includes, as the second digital filter unit, a second feedforward filter that performs a first digital filter processing on input data to the emphasis circuit, and
the emphasis circuit of the first transmission unit provides an output of the second feedforward filter as an output result.

4. The distortion compensation system according to claim 1 , wherein
the first reception unit receives each bit of the training pattern at an operation frequency,
the equalizer operates at an operation frequency higher than the operation frequency of the first reception unit so as to divide each bit of the training pattern into two or more sub-bits and the divided sub-bits have equal consecutive data values,
the equalizer converges the filter constant of the first digital filter unit so that errors in the sub-bits of the received training pattern are converged,
the first transmission unit of the first communication node operates at an equal frequency as the equalizer, and
the first transmission unit of the first communication node performs the distortion compensation on the normal data to be transmitted in units of the sub-bits using the converged filter constant of the first digital filter unit as at least a part of the filter constant of the second digital filter unit of the emphasis circuit, and then transmits the normal data.

5. The distortion compensation system according to claim 4 ,
wherein a quantity of the divided sub-bits is an odd number.

6. The distortion compensation system according to claim 5 ,
wherein the quantity of the divided sub-bits is equal to three.

7. The distortion compensation system according to claim 4 ,
wherein the first communication node further includes a filter which reduces components in a high-frequency region when the first communication node performs the distortion compensation on the normal data in units of the sub-bits and transmits the normal data to the second communication node.

8. The distortion compensation system according to claim 4 ,
wherein the second communication node further includes a filter which reduces components in a high-frequency region when the second communication node receives, from the first communication node, the normal data on which the distortion compensation has been performed in units of the sub-bits.

9. The distortion compensation system according to claim 7 , wherein
the filter has a cut-off frequency in the high-frequency region, and
the cut-off frequency is set to a Nyquist frequency corresponding to the operation frequency of the equalizer at which the equalizer divides each bit of the training pattern into the sub-bits.

10. The distortion compensation system according to claim 2 ,
wherein a quantity of filter taps in the second feedforward filter of the emphasis circuit is smaller than a quantity of filter taps in the first feedforward filter of the equalizer.

11. The distortion compensation system according to claim 2 ,
wherein a quantity of filter taps in the second feedback filter of the emphasis circuit is smaller than a quantity of filter taps in the first feedback filter of the DFE circuit.

12. The distortion compensation system according to claim 2 ,
wherein a quantity of the filter taps in the second feedforward filter of the emphasis circuit is smaller than a quantity of filter taps in the second feedback filter of the emphasis circuit.

13. The distortion compensation system according to claim 2 ,
wherein a quantity of digits of data which defines an error in a filter constant of the second feedforward filter of the emphasis circuit is smaller than a quantity of digits of data which defines an error in a filter constant of the first feedback filter of the DFE circuit.

14. The distortion compensation system according to claim 2 ,
wherein a quantity of digits of data which defines

Assignees

• Denso Corp

Inventors

• Akita Hironobu
• Ohtsuka Shigeki
• Matsudaira Nobuaki
• Yoshimoto Takahisa

Classifications

• H04L2025/03815

  Transmission of a training request · CPC title

• H04L25/03

  Shaping networks in transmitter or receiver, e.g. adaptive shaping networks · CPC title

• H04B3/14

  characterised by the equalising network used · CPC title

• H04L25/0278

  Arrangements for impedance matching · CPC title

• H04L25/0272

  Arrangements for coupling to multiple lines, e.g. for differential transmission · CPC title