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Ulllted States Patent [19]
`Nakagawa et al.
`
`USOO5774561A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,774,561
`Jun. 30, 1998
`
`[54] SUBBAND ACOUSTIC ECHO CANCELLER
`
`FOREIGN PATENT DOCUMENTS
`
`[75] Inventors. Aklra Nakagawa, Kokubunp, Yolchl
`-
`Haneda, Tokyo; Shoji Makino,
`
`-
`
`-
`
`_
`
`Machida; Suehiro Shimauchi; Junji
`Kojima, both of Tokyo, an of Japan
`
`[73] Assignee: Nippon Telegraph and Telephone
`C0rp., Tokyo, Japan
`
`[21] Appl. No.: 695,446
`.
`_
`Aug‘ 12’ 1996
`Flled'
`Foreign Application Priority Data
`
`[22]
`[30]
`
`Japan .................................. .. 7-206929
`[JP]
`Aug. 14, 1995
`[51] Int. Cl? ..................................................... .. H04B 3/20
`[52] us CL
`381/66. 381/94 1. 379/406,
`""""""""""""" "
`’
`'
`’
`’
`379/410
`381/66 94 1 71 1
`[58] Field of Search
`381
`408 41’0
`’
`’
`
`’
`
`[56]
`
`’
`’
`'
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`443547A2 8/1991 European Pat. Off. .
`91/1106‘)
`7/1991 WIPO '
`
`_
`_
`_
`Przmary Examzner—M1nsun Oh Harvey
`Attorney, Agent, or Firm—Pollock, Vande Sande & Priddy
`
`ABSTRACT
`[57]
`In a subband acoustic echo canceller Which generates an
`echo replica from a subband received signal Xk(II1) by an
`estimated echo path in each subband, subtracts the echo
`replica from a subband echo signal yk(m) by a subtractor to
`generate a subband error signal ek(m) and uses an adaptive
`algorithm in an echo path estimation part to estimate the
`transfer function of the estimated eCho path from the Sub_
`band error Signal 9Am) and the subband received signal
`Xk(II1) so that the subband error signal ek(m) approaches
`Zero, the sto -band attenuation of each band- ass ?lter of a
`P
`P
`received signal subband analysis part for generating the
`subband received signal Xk(II1) is set to be smaller than the
`stop-band attenuation of each band-pass ?lter of an echo
`subband analysis part for generating the subband echo signal
`Yk()hby? hfq yh "fh
`In tot ere
`attent e re uenc c aracter1st1cso t e
`subband received signals relative to the subband echo sig
`
`5,272,695 12/1993 Makino et a1. ....................... .. 379/410
`5,566,167 10/1996 Dottweiler ..
`..
`5,721,772
`2/1998 Haneda ................................. .. 379/410
`
`nals'
`
`16 Claims, 21 Drawing Sheets
`
`(A
`11
`
`[
`
`'
`
`9°
`
`l
`CHARAC
`FLAT
`
`x(t)
`
`18X
`
`x(n)
`REC SIG SUBBAND ANAL
`
`‘20
`
`1<_
`
`12
`m
`
`9k
`
`xo(m)
`
`1
`CHARAC
`FLAT
`
`'
`
`9N-l
`
`mm)
`
`1
`CHARAC
`FLAT
`
`'
`
`XN-1(m)
`FIL CHARAC
`
`5O
`
`EP
`
`SUBBAND
`SYNTJB
`
`SB
`SB EP
`EST 7’ EEP
`
`150
`
`SB EP
`SB
`sa EP
`EST _’ EEP """ " EST
`l
`
`15k
`
`s5
`EEP
`
`15N—1
`
`ECHO SIG
`SUBBAND
`ANAL
`3O
`
`J
`
`7‘! Wm)
`1 + 101m)
`17
`0
`
`19
`
`D/A
`em)
`
`14
`
`90m
`
`ekml)
`
`eN—1(m)
`
`714m)
`
`111-19“)
`
`(m)
`_ y
`r\ yk
`VP“
`~~~~ _.
`17k
`7 _‘~~__ __ _~,>
`1 +)/N_1(m)
`
`WAVES607_1007-0001
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 1 0f 21
`
`5,774,561
`
`e(t)
`
`WAVES607_1007-0002
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 2 0f 21
`
`5,774,561
`
`3:
`
`
`
`E< @051 Nd;
`
`WAVES607_1007-0003
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 3 0f 21
`
`5,774,561
`
`
`
`EvTzx EVNX A5; Evox
`
`
`
`
`
`
`
`26% ..... -- 26% 2B0 26%
`
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`
`4/ 4/
`
`ETZX E2 as; E?
`
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`
`um 81 um 81 gm B1 2m HE
`
`km .... -- &m &m %m
`/H/ 6/ (/ /)
`2a Na :N 0a.
`
`
`
`E3 19% m.o_.._
`
`WAVES607_1007-0004
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-0005
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 5 0f 21
`
`5,774,561
`
`O
`
`7Z/2
`1:C
`
`7C
`
`3 111/2
`
`NORMALIZED
`I FREQ
`2 75
`f5
`
`NORMALIZED
`> FREQ
`
`NORMALIZED
`9 FREQ
`
`POWER
`
`WAVES607_1007-0006
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-0007
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 7 0f 21
`
`5,774,561
`
`
`
`
`
`AEVTZX r59 Es; AEVQX
`
`E!
`
`he} :3 E; a?
`
`gm “mm gm 8m 9w HE um HE
`
`ham .... -- km km km
`
`4/ c/ (/ /) Ea mm :m 0a
`
`26mg .... -- 25% 26% 26%
`
`
`
`,0 5 J 5 2% NNN mm 0%
`
`N .0:
`
`WAVES607_1007-0008
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 8 0f 21
`
`5,774,561
`
`05 2E 9m O18 um 018 06 018 a (w 5 ;
`
`
`
`.5 .... -- mmm mmm “am
`
`rm E :m 0%
`
`A51; 3? ?x AC?
`
`26% ..... -- 25% 28¢ 25%
`
`
`
`
`5mm mm» ?m 0%
`
`1) </ (
`
`
`
`51; 2.3 E; E2;
`
`E; w 0E
`
`WAVES607_1007-0009
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 9 0f 21
`
`5,774,561
`
`FIG. 9
`
`O
`
`‘
`fPC
`
`7r/2
`
`,
`
`n
`
`, FREQ
`
`I:s
`2 7t
`
`FIG. 1 O
`
`Sl
`DIVIDING NUMBER~>M
`DECIMATION RATIO —>R /
`
`SETTING CHARACTERISTICS OF ECHO /- S2
`SIG BPF 5(2)
`O < f< fsc
`B(z)R =0 dB for
`=—b dB for fs¢< f
`—b+2010g1oR < Ref
`
`WHERE
`
`SETTING CHARACTERISTICS OF REC /— S3
`SIG BPF A(z)
`7Z<wsc 37Z/2
`WHERE w SC
`NOTES STOPBAND
`CUTOFF FREQ
`
`l
`
`TRANSFER
`FILTER COEFFICIENTS
`
`WAVES607_1007-00010
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 10 0f 21
`
`5,774,561
`
`FIG. 11
`
`Sl
`DIVIDING NUMBER—>M
`DECIMATION RATIO —>R /
`
`L
`
`SETTING CHARACTERISTICS OF ECHO SIG BPF B(z) :
`FOR TAPS n=—SbM, ---,O, ---,SbM
`OF IDEAL FIRTER HAVING RESPONSE
`b(n)=sT'n(n/M)/(n/M)
`DETERMINE SMALLEST Sb SATISFYING
`8(2)R =0 dB for
`O < f< fsc
`=—b dB for
`fsc< f
`
`AND
`
`SETTING FILTER CHARACTERISTICS OF REC SIG
`BPF A(z):
`FOR TAPS n=—SbM,---,O,---,S,,M
`OF IDEAL FILTER HAVING RESPONSE
`a(n)=sin(n/M)/(n/M)
`SELECT Sa SATISFYING
`Sa < Sb
`
`I
`
`s4
`TRANSFER
`FILTER COEFFICIENTS /
`
`/- S2
`
`/- S3
`
`WAVES607_1007-00011
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 11 0121
`
`5,774,561
`
`I
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`I
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`I
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`
`WAVES607_1007-00012
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 12 0f 21
`
`5,774,561
`
`IIIFIIIIIIIIIIIIIIIY'Y'IIIIIIIIIII'IIIIIII
`
`Emzoomsm 5
`
`cm?
`
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`
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`
`WAVES607_1007-00013
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00014
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 14 0f 21
`
`5,774,561
`
`0
`
`TC
`
`F|G.15B
`
`FIR FILTER
`
`F|G.15C
`
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`
`/
`
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`
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`
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`
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`
`WAVES607_1007-00015
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00016
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00017
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`U.S. Patent
`
`Jun. 30, 1998
`
`Sheet 17 0f 21
`
`5,774,561
`
`111|1|1|l|1|1|1|11|1||||||||l11||||l|L ||~
`Ow
`Om
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`
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`
`WAVES607_1007-00018
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00019
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00020
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00021
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00022
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00023
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00024
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`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00025
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00026
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`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00027
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00028
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00029
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`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00030
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`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
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`WAVES607_1007-00031
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007
`
`

`
`WAVES607_1007-00032
`
`Petitioner Waves Audio Ltd. 607 - Ex. 1007

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