Signal transmission apparatus, distortion compensation apparatus, and signal transmission method

Patent metadata

Field	Value
Publication number	US-9596120-B2
Application number	US-201415024891-A
Country	US
Kind code	B2
Filing date	Aug 26, 2014
Priority date	Sep 26, 2013
Publication date	Mar 14, 2017
Grant date	Mar 14, 2017

Abstract

A signal conversion unit ( 120 ) of a signal transmission apparatus ( 10 ) includes an in-band distortion compensation analog circuit unit ( 122 ) that generates, for each band, an in-band distortion compensation signal for compensating for in-band intermodulation distortion occurring due to frequency mixing of RF signals of a single band, the distortion being included in RF signals which are output from an amplification unit ( 130 ), and causes the generated signal to be carried by the RF signals corresponding to the single band, and an inter-band distortion compensation analog circuit unit ( 124 ) that generates, for each combination of two bands, an inter-band distortion compensation signal for compensating for cross-modulation distortion occurring due to frequency mixing of RF signals between a plurality of bands which are input to the amplification unit ( 130 ), and causes the generated signal to be carried by each of the RF signals corresponding to the two bands.

First claim

The invention claimed is:

1. A signal transmission apparatus comprising:
a signal generation unit that outputs a plurality of analog baseband signals such that each of the plurality of analog baseband signals corresponds to a respective band from among a plurality of bands;
a signal conversion unit that converts each of the plurality of output analog baseband signals into a respective radio frequency (RF) signal of the corresponding band; and
an amplification unit that collectively amplifies each converted RF signal,
wherein the signal conversion unit includes
an in-band distortion compensation analog circuit unit that generates, for each respective band, an in-band distortion compensation signal for compensating for in-band intermodulation distortion occurring due to frequency mixing of RF signals of the respective band, the distortion being included in each respective RF signal which is output from the amplification unit, and causes the respective generated in-band distortion compensation signal to be carried by the RF signals corresponding to the respective band, and
an inter-band distortion compensation analog circuit unit that generates, for each respective pair of bands from among the plurality of bands, an inter-band distortion compensation signal for compensating for cross-modulation distortion occurring due to frequency mixing of RF signals among the plurality of bands which are input to the amplification unit, and causes the respective generated inter-band distortion compensation signal to be carried by each respective RF signal that corresponds to one of the respective pair of bands.

2. The signal transmission apparatus according to claim 1 , wherein for each respective band, the in-band distortion compensation analog circuit unit generates the corresponding in-band distortion compensation signal by using parameters based on the in-band intermodulation distortion occurring due to the mixing of the RF signals of the respective band in the amplification unit, and
for each respective pair of bands from among the plurality of bands, the inter-band distortion compensation analog circuit unit generates the respective inter-band distortion compensation signal by using parameters based on the cross-modulation distortion occurring due to the mixing of the RF signals among the plurality of bands in the amplification unit.

3. The signal transmission apparatus according to claim 2 , wherein the inter-band distortion compensation analog circuit unit includes:
a first multiplication unit that multiplies a first analog baseband signal from among the plurality of analog baseband signals by an amplitude square value of a second analog baseband signal from among the plurality of analog baseband signals;
a second multiplication unit that multiplies the second analog baseband signal by an amplitude square value of the first analog baseband signal;
a compensation signal generation unit that generates the respective inter-band distortion compensation signal by correcting an amplitude and a phase of each respective analog baseband signal which is outputted by one of the first multiplication unit and the second multiplication unit, using the parameters based on the cross-modulation distortion; and
at least one quadrature transformation unit that transforms each respective analog baseband signal provided with the corresponding inter-band distortion compensation signal into a respective RF signal of the corresponding band.

4. The signal transmission apparatus according to claim 1 , wherein for each respective pair of bands from among the plurality of bands, the inter-band distortion compensation analog circuit unit generates the corresponding inter-band distortion compensation signal by using parameters based on cross-modulation distortion occurring due to the mixing of the RF signals among the plurality of bands in the amplification unit, and
for each respective band, the in-band distortion compensation analog circuit unit generates the corresponding in-band distortion compensation signal by using parameters based on the in-band intermodulation distortion occurring due to the mixing of the RF signals of the respective band in the amplification unit and in-band intermodulation distortion occurring in a process of generating the corresponding inter-band distortion compensation signal in the inter-band distortion compensation analog circuit unit.

5. The signal transmission apparatus according to claim 4 , wherein the inter-band distortion compensation analog circuit unit includes:
at least one quadrature modulation unit that converts each analog baseband signal which is input to the inter-band distortion compensation analog circuit unit into a respective RF signal of the corresponding band; and
a compensation signal generation unit that generates the inter-band distortion compensation signal by correcting an amplitude and a phase of the respective converted RF signal by using the parameters based on the cross-modulation distortion.

6. The signal transmission apparatus according to claim 1 , further comprising a control unit that controls the signal conversion unit,
wherein the control unit includes:
a signal detection unit that detects an RF signal which is output from the amplification unit; and
a distortion detection unit that detects a signal distortion component included in the detected RF signal,
wherein the control unit provides the in-band distortion compensation analog circuit unit with parameters used for generating the corresponding in-band distortion compensation signal and provides the inter-band distortion compensation analog circuit unit with parameters used for generating the corresponding inter-band distortion compensation signal, based on the detected signal distortion component.

7. The signal transmission apparatus according to claim 6 , wherein the distortion detection unit includes:
a demultiplexing unit that demultiplexes, for each respective band, at least one RF signal detected by the signal detection unit;
a selection unit that selects one RF signal from among the at least one RF signal demultiplexed by the demultiplexing unit;
a variable local oscillation (LO) signal generation unit that outputs a LO signal;
a microcontroller that controls a frequency of the LO signal which is output from the variable LO signal generation unit based on a carrier frequency of the RF signal selected by the selection unit;
a mixer unit that mixes the selected RF signal with the LO signal to generate an intermediate frequency (IF) signal;
a filtering unit that filters noise from the IF signal and then passes only a signal distortion component of a frequency band corresponding to signal distortion included in the IF signal; and
a wave detection unit that down-converts a frequency of the signal distortion component to a baseband range, and
wherein the control unit provides the in-band distortion compensation analog circuit unit with the parameters used for generating the corresponding in-band distortion compensation signal and provides the inter-band distortion compensation analog circuit unit with the parameters used for generating the corresponding inter-band distortion compensation signal, based on the signal distortion component detected by the distortion detection unit.

8. A distortion compensation apparatus that compensates for in-band intermodulation distortion in each of a plurality of bands and cross-modulation distortion between respective pairs of bands from among the plurality of bands, the in-band intermodulation distortion and the cross-modulation distortion being included in RF signals which are output from an amplification unit that collectively amplifies radio frequency (RF) signals, the apparatus comprising:
an in-band distortion

Assignees

• Nec Corp

Inventors

• Yamanouchi Shingo

Classifications

• H04B1/04

  Circuits · CPC title

• H03F2201/3215

  To increase the output power or efficiency · CPC title

• H04B1/0475

  with means for limiting noise, interference or distortion (H04B1/0483 takes precedence) · CPC title

• H04L27/367 Primary

  using predistortion · CPC title

• H03F1/32

  Modifications of amplifiers to reduce non-linear distortion (by negative feedback H03F1/34) · CPC title