PATENT NUMBER
`PATENT NUMBER
`
`6049607
`IIII~IIII~IIIIIIIIII~IIIIII~IIIIIIIIIIII
`
`6049601
`
`U.S. UTILIW PATENT APPLICATION
`U.S. UTILITY PATENT APPLICATION
`J/II
`PATENT DATE
`S~Jft:NED +n: q.A. J. ,;
`
`; \
`
`APR 1 1 2000
`
`O.I.P.E., /
`
`, ' '
`
`SECTOR CLASS
`
`-3g
`
`SUBCLASS
`
`.. ')
`;
`
`ART UNIT
`"'
`2 --7'1(' ';
`, "
`J
`"
`r .)FILED WITH: 0 DISK (CRF) 0 FICHE
`DrsK (cRF) flrtcne
`. ,IHLED wrH:
`
`/
`
`'
`
`in pockEi on dght iGid€
`tlap)
`(Attach€d
`(Attached in pocket on right inside flap)
`
`PREPARED AND APPROVED FOR ISSUE
`PREPARED AND APPROVED FOR ISSUE
`
`ORIGINAL
`
`ISSUING CLASSIFICATION
`ISSUING CLASSIFICATION
`CROSS REFERENCE(S)
`
`CLASS
`
`SUBCLASS
`
`CLASS
`
`SUBCLASS (ONE SUBCLASS PER BLOCK)
`SUBCLASS (ONE SUBCLASS PER BLOCK)
`
`INTERNATIONAL CLASSIFICATION
`
`D Continued on Issue Slip Inside File Jacket
`Continusd on lssue Slip Inside File Jackot
`
`Total Clai,/
`I
`37
`D a) The term ofthis patent
`It } r'j I--_N_O_T_I_C_E_O_F_A_L_L_O_W_A_N_C_E_M_AI_L_E_D_-f
`'LJ a)Theterm olthis Patent
`n,vr- SURJYJ!/'
`)?y Al >"/
`(date) J'8C#f!f:.f 5Ifl/IJr: S1.IR //,,/ Itll ~
`(oate»)~,/ d I '" 7" <C)'.
`subsequent to
`(date)
`subsequent to --
`ir6istifrEtmtneo
`has been disclaimed.
`(Assistant Examiner)
`has been disclaimed.
`C7'\
`D b) The term of this patent shall
`-41-
`Ll b) The term of this patgnt shall
`not extend beyond the expiration date
`nol extend beyond the sxpiration dato
`of U.S Patent. No. _____ ~
`of U.S Patent. No. --
`FORESTER W. ISEN
`SUPERVISORY PATENT EXAMINER
`SUPERVISORY PATENT EXAMINER
`W7oqilil-
`1iCf;ltiQLQ~) CENTER 270Qoate)
`
`CLAIMS ALLOWED
`Print Claim O.G.
`
`(oaie)
`
`Amount Due
`
`ISSUE BATCH
`ISSUE BATCH N
`
`(/c'l
`GO/
`
`| EnlullrAL
`l-]
`I IDISCLAIMER
`
`Sheets 7
`7
`
`DRAWINGS
`
`,7
`
`D c) The terminal _months of
`of
`L-J c) The terminal
`this patent have been disclaimed.
`this patent have been disclaimed.
`-months
`
`WARNING:
`WARNING:
`code Title 35' soctions 122' !B'l and
`Ths informagon disctosed h€rein may b€ resrricted. unauthorized disclosure may be prohlbit€d.by
`llr€ VJ'1!e9-:.lates
`The Information disclosed herein may be restricted. Unauthorized disclosure may be prohibited by the United States Code Title 35. Sections 122. )81 and 368.
`posgession outside the u.s. Pat€nt & Trademark otfice is restricted to authoflzed €mployees and contraclors only'
`Possession outside the U,S. Patent & Trademark Office is restricted to authorized employees and contractors only.
`Form PT()'436A
`rom PTO-430A
`(Rev, 10197)
`(R6v. 1087)
`
`{LABEL AREA) F ,e
`
`Issue aa n ~
`
`(FACE)
`
` RTL607_1020-0001
`
`Realtek 607 Ex. 1020
`
`

`
`PATENT ARPLICA nON
`PF.TEHT ABP|-rcA?ION
`
`I tiliit ilili ililt tff t ffiiiltffi ilil tilt
`1 IIII!I 1111111111111 MIIII 1111 1111
`ru
`09157035
`09157C35
`
`Jcl-!c.,U-,!-:^ J?o '
`jcIlS'U.S: PTO'
`0.9/157035
`lt?035
`," '1~~!I~~~~"11111111
`CONTENTS
`CONTENTS
`Date received
`(Incl. C. of M.)
`or
`Date Mailed
`
`I~ .. riALS ___ _
`llrr fIALS -*
`sEp2s 9826
`SEP 2 5 S 8 26
`-
`
`Oate received
`Oate recelved
`(Incl. C. of M.)
`(lncl. C. ot M.)
`or
`ot
`Date Mailed
`Date Malled
`42._' __ ___ . ______ _
`42.
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`^
`1j( 43.
`2447/
`1
`43.
`~~~m~o/n5':--
`, lI fTT ^n
`44. __________ _
`1lk1 Lt
`44._
`tJl;N. z7 4s. _
`M~'.fj,UL~~~>""""""_rrr /. ';>. 7{ 45. ____________ _
`, 3' 17 -lv
`~~~~~n 3--- 19-/(j
`46. _ __ __ _ ___ _ __ _
`La
`3-O4 47.--
`~~~ __ , -(9--li
`
`47.
`48. __________ __ _
`48.
`49. _ _ _ __ _ _ _ _
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`50. _ _ __ _ _ __ _ ___ _
`50.
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`10.
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`11.
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`56. ___ __________ _
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`59. _________ _
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`60. ______ ~--
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`76.
`n. ___________ _
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`80. __________ _
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`81.
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`82.
`82._---'-_=-=~.------
`
`14.
`15. _ ______ _ _
`15.
`16. ____________ _
`16.
`17. ___ __ __ _ _
`17.
`18. ____________ _
`18.
`19. ___ _____ _
`19.
`2,0. __ __ ____ ____ _
`29.
`21. _____ ___ _
`21.
`22. ________ ____ _
`22.
`23. _____________ _
`23.
`24. ________ ____ __
`24.
`25. _ ____________ _
`25.
`26. _ _ --'-__ _______ _
`26.
`27. __ __ __ __ _
`27.
`28. _ ____________ _ _
`28.
`29. __ _ _ _ ___ ____ _
`29.
`30. ________ _
`30.
`31. _ ____________ _ _
`31.
`32. __ __ ________ __
`32,
`33 ._ _ __ __ _ __ _____
`33.
`34. _ _ _ __ _ __ ____ __
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`35. __ _ _ __ _ _____ _
`35.
`36. _ ______ _ _
`36.
`37 .. __ _ _ __ _ _____ _
`37..
`38. ____________ _
`38.
`39. __ _ _ _ _ __ _ __ __ _
`39.
`40. ___ _____ _
`40.
`41._________ ____
`41.
`(FRONT)
`
` RTL607_1020-0002
`
`

`
`I
`
`/ ,1
`
`ISSUE SdP S'fAPLE'AREA (for adc\\tional cro~s references)
`ISSUE SuIP STAPLE'AREA (for adc'tional cross references)
`
`.
`
`POSITION
`
`INITIALS
`
`~
`
`10 NO;
`
`DATE
`
`0/
`'-' I~.Y
`~
`q-2~211
`r~ ~I
`~ .\
`/tJ_/-vY
`
`N I An
`
`FEE DETEkMINATION
`O.I.P .E. CLASSIFiER
`FORMALITY REVIEW
`
`\J J
`
`I.~
`(jffJ~L
`INDEX OF CLAIMS
`~ ................................. Rejected
`N ................................. Non-elected
`..,..... Non-elected
`..,..,.. Reiected
`= ................................. Allowed
`I ................................. Interference
`..,,.... Interference
`,...,... Allowed
`(Through numeral) Canceled
`A ................................. Appeal
`...,.... Appeal
`(Through numeral) Canceled
`o ................................. Objected
`................................. Restricted
`"'.'.'. obiected
`....,... Restricted
`
`Claim
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`,f
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`Date
`
`Claim
`Claim
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`Date
`DatE
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`Claim
`Claim
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`Date
`Date
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`~ I 0
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`o
`lr
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`0
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`11C
`11~
`113
`114
`115
`116
`117
`118
`119
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`111
`112
`113
`114
`115
`116
`117
`118
`h rsl
`119
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`20
`F20l
`121
`122
`123
`124
`125
`26
`127
`128
`29
`130
`131
`132
`3
`13
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`13€
`3
`38
`39
`40
`141
`14.
`14<
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`45
`46
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`14€
`149
`150
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`.
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`01 "!
`G
`~ C5
`51
`52
`53
`54
`55
`56
`57
`58
`59
`60
`61
`62
`63
`64
`65
`66
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`70
`81
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`Itn 10 :::::
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`1..1 13 I:;:
`/1114 ;:::
`/J 15 '-:::::
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`17 17 -
`I g- 18 1-=
`[/q 19 -
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`~20 1=
`d( 21 I.:::::
`.~ . .22 1-::
`;..3 23 1-:::
`6?4 2j, 1==
`;t~ 25 0.::
`'.?I 2'S 1.-:::
`27 1=
`28 I;:::::
`29 1-
`30 I-
`i/ 31 1-
`13.2. 32 ==
`lll33 ::::
`134'34 -:::
`B!35 -::::
`l3(; 36 ::::.
`l3J 37 :=
`38
`39
`40
`41
`42
`43
`44
`45
`46
`47
`48
`49
`50
`
`If more than 150 claims or 10 actions
`lf more than 150 claims or 10 actions
`,c;;taple additional sheet here
`ataple additional sheet here
`
`(LEFT INSIDE~
`(LEFT INSIDE)
`
`.. 4~·
`
` RTL607_1020-0003
`
`

`
`SEARCHED
`SEARCHED
`
`SEARCH NOTES
`SEARCH NOTES
`(INCLUDING SEARCH STRATEGY)
`(TNGLUDTNG SEARCH STRATEGY)
`
`Date
`p"\\ \1l
`lzlr Iri
`
`Exmr.
`
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`3/15 #
`
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`
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`37'1
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`INTERFERENCE SEARCHED
`Class
`Date
`SUb.
`Exmr.
`tultlr
`
`cL.e..J...
`
`CoS>.
`0 -
`at a*
`~~~ ?-'ove.-
`
`(-z.,/3h 1 V / '
`
`(RIGHT OUTSIDE)
`(RIGHT OUTSIDE)
`
` RTL607_1020-0004
`
`

`
`ATTACH
`ATTACH
`DISK/FICHE
`DISI(FICHE
`ENVELOPE
`ENVELOPE
`HERE
`HERE
`
`(
`
`(RtcHT StDE)---
`(RIGHT SIDE)··~·
`
` RTL607_1020-0005
`
`

`
`PATENT
`PATENT
`670025-7007
`670025-7007
`IN TIIE I'NITED STATES PATENT AIVD TRJADEMARK OFFICE
`IN THE UNITED STATES PATENT AND TRADEMARK OFFICE
`APPI,ICATION tr'OR I,ETTERS PATENT
`APPLICATION FOR LETTERS PATENT
`
`-tE
`
`S*g
`
`,Joseph MAR;A,SH and Baruch BERDUGO
`Joseph MARASH and Baruch BERDUGO
`
`Applicant:
`Applicant:
`Title:
`Title:
`INTERFERENCE CAI{CELING METHOD AI{D APPARJATUS
`INTERFERENCE CANCELING METHOD AND APPARATUS
`of Pages (Spec) :
`No.
`No. of Pages (Spec)
`20
`2O
`37 (pp 21-28)
`of Claims:
`No.
`No. of Claims:
`37 (pp 21-28)
`of pages (Abstract) : 1 (p 29)
`No.
`No. of pages (Abstract)
`1
`(p 29)
`Sheets of Drawings:
`7 (Figs . L-7)
`Sheets of Drawings:
`7 (Figs. 1-7)
`Ma i r ins r*"l*Rl,?i2'W
`Mailing Label NumberJ:'LSIJ.:v 1(,.0 qs
`EXPRESS ~~ I?r-
`Date of DeposiE.
`SeDLember 18, 199e
`Date of Deposit
`September 18, 1998
`rherebycartify@
`I hereby certify that this paper or fee is being
`deposit.ed with t.he ttnited Stat.es poscal Seryice
`deposited with the United States Postal Service
`rExpress Mail Post Office to Addresseen Sewice
`"Express Mail Post Office to Addressee" Service
`under 37 CFR 1-10 on the date indicated above and
`under 37 CFR 1.10 on the date indicated above and
`is addressed to the Assistant. Comissioner for paLentss.
`is addressed to the Assistant Commissioner for Patents,
`20231, BOX NEW PATENT APPLICATION
`WaShingto~. 20231, BOX NEW PATENT APPLICATION
`uJMJ WflE/l
`
`person
`(Typed or printed name of person
`r fee
`mailing p. per
`
`Thomas J. Kowalski
`Thomas J. Kowalski
`Rdg. No. 32 , L4'7
`Reg. No. 32,147
`I. Marc Asperas
`I. Marc Asperas
`Regf . No. 37,274
`Reg. No. 37,274
`IIAUG' IJLP
`FROMMER LAWRENCE & HAUG, LLP
`FROMMER I,A$IRENCE &
`745 Fifth Avenue
`745 Fifth Avenue
`New York, New York
`New York, New York 10151
`10151-
`(2r2) 588-0800
`(212) 588-0800
`FAX (272) 588-0500
`FAX (212) 588-0500
`
`ANDREA. 37\LAMAR\7007. COV
`ANDREA. 3 ? \I,AMAR\ ? O O ? . COV
`
` RTL607_1020-0006
`
`

`
`tt{
`
`-*
`
`-
`
`e
`
`FROMMER LAWRENCE & HAUG LLP
`745 Fifth Avenue
`New York, New York 10151
`(2t2) s88-
`Tel (212) 588-0800
`Fax QL2, 588-0500
`Fax (212) 588-0500
`PATENT APPLICATION TRAI{SMITTAI,
`PATENT APPLICATION TRANSMITTAL
`Date: September 18, 1998
`Date: September 18, 1998
`670025-7007
`Re:
`670025-7007
`Re:
`THE COMMISSIONER OF PATENTS AND TRADEMARKS
`THE COMMISSIONER OF PATENTS AND TRADEMARKS -
`Box PATENT APPLICATION
`Box PATENT APPLICATION
`Washington, D. C. 20231,
`Washington, D.C. 20231
`
`TO:
`TO:
`
`Sir:
`Sir:
`iling in the United staLes Patent and
`With reference tO~iling in the United States Patent and
`Lhe name of:
`applicat. :-on fuft PaLent in
`application ~. patent in the name of:
`Trademark Office
`o PH MARASH an~RUCH BERDUG.o.
`ilenasn anf,EKnuqE JEBDTI
`IMrERFERENCE CAlICEr.rre @Us
`entitled:
`entitled: INTERFERENCE CANCELING IH!I'f'HOf) 1dffi APJilAR2\TUS
`following are enclosed:
`following are enclosed:
`(20 pages) and One Page of Abstract (p. 29)
`29 )
`Specifiiation
`Specification (20 pages) and One Page of Abstract (p.
`:-z Claims (includi.,g-3 independent claims,' pp' 2'L-28)
`37 Claims (including ~ independent claims; pp. 21-28)
`? Sheet.s of Drawings (Figs . 1"-1)
`2 Sheets of Drawings (Figs. 1-7)
`-#igtted Declaration and Power of Attorney (2 pages)
`~igned Declaration and Power of Attorhey (2 pages)
`in response to a
`fee will be paid later,
`The filing
`The filing fee will be paid later, in response to a
`Notice to File Missing Parts. Kindly accord the
`Notice to File Missing Parts. Kindly accord the
`application a September 18, 1-gg| filing date and
`application a September 18, 1998 filing date and
`address all communicati-ons to the undersigned at the
`address all communications to the undersigned at the
`address above.
`address above.
`submitted,
`fu11y
`Respect
`for
`
`The
`The
`K
`K
`K
`K
`K
`
`xxxxX
`
`:i:
`
`By:
`
`Thomas J
`
`Mairins ,^o"\"n*Yi2'W
`SepEember 18,.1998 , ,
`Date of DeposiE
`thaE t.his paper or fee is being
`I hereby certify
`deposiEed with che unj-ted stsaies Postal seryice
`'rExpress Mail post office
`!o Addressee" Serice
`under 37 CFR r-1O on tshe date indicated abowe and
`is addressed to the Assistant Comnissioner for Patents,
`20231, BOX NEW PATENT APPI,ICATION
`
`name
`(~d o.r. printed name of per~
`
`~7E2l~
`
`(Signature of person mailing paper or fee)
`
`32,147 -
`No. 32,I4'l
`_I -
`
` RTL607_1020-0007
`
`

`
`t5103{
`
`PATENT
`PATENT
`670025-7007
`670025-7407
`
`TITLE OF THE INVENTION
`TITLE OF THE INVENTION
`
`INTERFERENCE CANCELING METHOD AND APPARATUS
`INTERFERENCE CANCELING METHOD AND APPARATUS
`
`RELATED APPLICATIONS
`RELATED APPLICATIONS
`
`Reference is made to co-pending u.s. applications Serial Nos. 08/672,899
`Reference is made to co-pending U.S. applications Serial Nos. 08/672,899
`
`(allowed), 09/130,923, 08/840,159, 091059,503 and 09/055,709, each of which is hereby
`(allowed), 09/130,923,08/840,159,09/059,503 and 09/055,709, each of which is hereby
`
`incorporated herein by reference; and each and every document cited in those applications, as
`incorporated herein by reference; and each and every document cited in those applications, as
`
`well as each and every document cited herein, is hereby incorporated herein by reference.
`well as each and every document cited herein, is hereby incorporated herein by reference.
`
`rIELD OF THf, IIIVENTION
`FIELD OF THE INVENTION
`
`The present invention relates to an interference canceling method and apparatus
`The present invention relates to an interference canceling method and apparatuS
`
`and, for instance, to an echo canceling method and apparatus which provides echo-canceling in
`and, for instance, to an echo canceling method and apparatus which provides echo-canceling in
`
`~dJ
`Ui
`
`full duplex communication, especially teleconferencing communications.
`full duplex communication, especially teleconferencing communications.
`
`BACKGROUND OF THE INVENTION
`BACKGROUND OF THE INVENTION
`
`Tele-conferencing plays an extremely important role in commUnications today.
`Tele-conferencing plays an extremely important role in communications today.
`
`The teleconference, particularly the telephone conference call, has become routine in business, in
`The teleconference, particularly the telephone conference call, has become routine in business, in
`
`part because teleconferencing provides a convenient and inexpensive forum by which distant
`part because teleconferencing provides a convenient and inexpensive forum by which distant
`
`business interests communicate. Internet conferencing, which provides a personal forum by
`business interests communicate. Internet conferencing, which provides a personal forum by
`
`which the speakers can see one another, is enormously popular on the home front, in part because
`which the speakers can see one another, is enormously popular on the home front, in part because
`
`it brings together distant family and friends without the need for expensive travel.
`it brings together distant family and friends without the need for expensive travel.
`
`ln a teleconferencing system, the sounds present in a room, hereinafter referred to
`In a teleconferencing system, the sounds present in a room, hereinafter referred to
`
`as the "near-end room" such as those of a near-end speaker are received by a microphone,
`as the "near-end room" such as those of a near-end speaker are received by a microphone,
`
`ANDEFA.3?\trAIVTAIIUO9 I.AI'3
`ANDREA.37ILAMARI209I.AP3
`
`1
`
` RTL607_1020-0008
`
`

`
`PATENT
`PATENT
`670025-7007
`67002s-7007
`
`transmitted to a "far end system" and broadcast by a far-end loudspeaker. Similarly, the far-end
`transmitted to a "far end system" and broadcast by a far-end loudspeaker. Similarly, the far-end
`
`speaker is received by the far-end microphones and transmitted to the near-end system, and
`speaker is received by the far-end microphones and transmitted to the near-end system, and
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`broadcast by the near-end loudspeaker. The near-end microphone receives the broadcasted
`broadcast by the near-end loudspeaker. The near-end microphone receives the broadcasted
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`sounds along with their reverberations and transmits them back to the far-end, together with the
`sounds along with their reverberations and transmits them back to the far-end, together with the
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`desired signals generated by, for example, speakers at the near-end, thereby resulting in a
`desired signals generated by, for example, speakers at the near-end, thereby resulting in a
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`disturbing echo heard by the speaker at the far-end. The far-end speaker will hear himself after
`disturbing echo heard by the speaker at the far-end. The far-end speaker will hear himself after
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`the sound has traveled to the near-end system and back, thereby resulting in a delayed echo
`the sound has traveled to the near-end system and back, thereby resulting in a delayed echo
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`which will annoy and confuse the far-end speaker. The problem is compounded in video and
`which will annoy and confuse the far-end speaker. The problem is compounded in video and
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`internet conferencing systems where the delay is more extremely pronounced.
`internet conferencing systems where the delay is more extremely pronounced.
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`The simplest way to overcome the problem of echo is by blocking the near-end
`The simplest way to overcome the problem of echo is by blocking the near-end
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`3-i
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`S:
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`"=::;:
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`microphone while the far-end signal is broadcast by the near-end loudspeaker. Sometimes
`~t1 microphone while the far-end signal is broadcast by the near-end loudspeaker. Sometimes
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`referred to as "ducking", the technique of blocking the microphone is effectively a half-duplex
`referred to as "ducking", the technique of blocking the microphone is effectively a half-duplex
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`communication. Problematically, if the microphone.is blocked for a prolonged period to avoid'
`communication. Problematically, if the microphone. is blocked for a prolonged period to avoid-
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`transmission of the reverberations, the half-duplex communication becomes a significant
`transmission of the reverberations, the half-duplex communication becomes a significant
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`drawback because the far-end speaker will lose too much of the near-end speaker. In the video or
`drawback because the far-end speaker will lose too much of the near-end speaker. In the video or
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`lnternet conferencing system, where the delay created by the communication lines is extreme,
`Internet conferencing system, where the delay created by the communication lines is extreme,
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`ducking becomes quite annoying.
`ducking becomes quite annoying.
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`A more complex method to avoid echo is to employ an echo canceling system
`A more complex method to avoid echo is to employ an echo canceling system
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`which measures the signals send from the far-end and broadcast at the near-end loudspeaker,
`which measures the signals send from the far-end and broadcast at the near-end loudspeaker,
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`estimates the resulting signal present at the near-end microphone (including the reverberations)
`estimates the resulting signal present at the near-end microphone (including the reverberations)
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`and subtracts those signals representing the echo from the near-end microphone signals. The
`and subtracts those signals representing the echo from the near-end microphone signals. The
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`echo-free signals are then transmitted back to the far-end system.
`echo-free signals are then transmitted back to the far-end system.
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`In order to reduce the echo from the near-end microphone signal, it is required to
`In order to reduce the echo from the near-end microphone signal, it is required to
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`obtain the transfer function that expresses the relationship between the near-end loudspeaker
`obtain the transfer function that expresses the relationship between the near-end loudspeaker
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`signal and the reverberations as they actually appear at the near-end microphone. This transfer
`signal and the reverberations as they actually appear at the near-end microphone. This transfer
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`function depends on the relative position of the near-end loudspeaker to the near-end
`function depends on the relative position of the near-end loudspeaker to the near-end
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`microphone, the room structure, position of the system and even the presence of people in the
`microphone, the room structure, position of the system and even the presence of people in the
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`room. Since it is impossible to predict these parameters a priori, it is preferred that the echo-
`room. Since it is impossible to predict these parameters a priori, it is preferred that the echo-
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`canceling system updates the transfer function continuously in real time.
`canceling system updates the transfer function continuously in real time.
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`The adaptation process by which the echo-canceling system is updated in real
`The adaptation process by which the echo-canceling system is updated in real
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`time may be an LMS (least means square) adaptive filter (Widrow, et al., Proc. IEEE, vol. 63, pp.
`time may be an LMS (least means square) adaptive filter (Widrow, et al., Proc. IEEE, vol. 63, pp.
`
`1692-17|6,Proc. IEEE, vol. 55, No. 12, Dec.1967)with the far-end signal used as the reference
`1692-1716, Proc. IEEE, vol. 55, No. 12, Dec. 1967) with the far-end signal used as the reference
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`li
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`signal. The LMS filter estimates the interference elements (echoes) present in the interfered
`signal. The LMS filter estimates the interference elements (echoes) present in the interfered
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`channel by multiplying the reference channel by a filter and subtracting the estimated elements
`channel by multiplying the reference channel by a filter and subtracting the estimated elements
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`from the interfered signal. The resulting output is used for updating the filter coefficients. The
`from the interfered signal. The resulting output is used for updating the filter coefficients. The
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`adaptation process will converge when the resulting output energy is at a minimum, leaving an
`adaptation process will converge when the resulting output energy is at a minimum, leaving an
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`echo-free signal.
`echo-free signal.
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`Important to the adaptation process is the selection of the size of the adaptation
`lmportant to the adaptation process is the selection of the size of the adaptation
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`step of the filter coefficients. In the standard LMS algorithm the step size is controlled by a
`step of the filter coefficients. In the standard LMS algorithm the step size is controlled by a
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`predetermined adaptation coefficient, the level of the reference channel and the output level. In
`predetermined adaptation coefficient, the level of the reference channel and the output level. In
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`other words, the adaptation process will have bigger steps for strong signals and smaller steps for
`other words, the adaptation process will have bigger steps for strong signals and smaller steps for
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`weaker signals.
`weaker signals.
`A better behaved system is one in which its adaptation steps are independent of
`A better behaved system is one in which its adaptation steps are independent of
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`the reference channel levels. This is accomplished by normalizing the adaptation coeffrcient by
`the reference channel levels. This is accomplished by normalizing the adaptation coefficient by
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`the reference channel energy, this method is called the Normalized Least Mean Square (NLMS)
`the reference channel energy, this method is called the Normalized Least Mean Square (NLMS)
`as, for example, described in see for example "e Family of Normalirc
`", Scott
`as, for example, described in see for example "A Family of Normalized LMS Algorithms", Scott
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`C. Douglas, IEEE Signal Processing Letters, Vol. 1, No. 3, March 1994. [t should be noted that
`C. Douglas, IEEE Signal Processing Letters, Vol. 1, No.3, March 1994. It should be noted that
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`the energy estimator, if not designed properly, may fail to track when large and fast changes in
`the energy estimator, if not designed properly, may fail to track when large and fast changes in
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`the level of the reference channel occur. Thus, the normalized coefficient may be too big during
`the level of the reference channel occur. Thus, the normalized coefficient may be too big during
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`-.::
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`the transition period, and the filter coefficient may diverge-
`the transition period, and the filter coefficient may diverge.
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`Another problem is that the adaptive process feeds the output back to determine
`Another problem is that the adaptive process feeds the output back to determine
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`the new filter coeffrcients- When the interfering elements in the signal are less pronounced than
`the new filter coefficients. When the interfering elements in the signal are less pronounced than
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`the non-interfering signal, there is not much to reduce and the filter may diverge.or converge to a
`the non-interfering signal, there is not much to reduce and the filter may diverge .or converge to a
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`~JJ
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`wrong value which results in signal distortions-
`wrong value which results in signal distortions.
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`When properly converged, the adaptive filter actually estimates the transfer
`When properly converged, the adaptive filter actually estimates the transfer
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`function between the far-end loudspeaker signal and the echo elements in the main channel.
`function between the far-end loudspeaker signal and the echo elements in the main channel.
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`However, changes in the room will effect a change in the transfer function and the adaptive
`However, changes in the room will effect a change in the transfer function and the adaptive
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`process will adapt itself to the new conditions. Sudden or quick changes, in particular, will take
`process will adapt itself to the new conditions. Sudden or quick changes, in particular, will take
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`the adaptive filter time to adjust for and an echo will be present until the filter adapts itself to the
`the adaptive filter time to adjust for and an echo will be present until the filter adapts itself to the
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`new conditions.
`new conditions.
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`ln order to improve the audio quality, sometimes a number of microphones are
`In order to improve the audio quality, sometimes a number of microphones are
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`used instead of a single one. This system either selects a different microphone each time
`used instead of a single one. This system either selects a different microphone each time
`someone is speaking in the room or creates a directional beam using a linear combination of
`someone is speaking in the room or creates a directional beam using a linear combination of
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`microphones- By multiplexing the microphones or steering the directional audio beam, the
`microphones. By multiplexing the microphones or steering the directional audio beam, the
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`relationship between the loudspeaker signal and the audio signal obtained by the microphones
`relationship between the loudspeaker signal and the audio signal obtained by the microphones
`can be changed. Problematically, each time such a transition takes place, an echo will "leak" into
`can be changed. Problematically, each time such a transition takes place, an echo will "leak" into
`the system until the new condition has been studied by the adaptive filter. To allow the use of a
`the system until the new condition has been studied by the adaptive filter. To allow the use of a
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`~:~
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`steerable directional beam and prevent the transient echo, one can either perform continuous
`steerable directional beam and prevent the transient echo, one can either perform continuous
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`echo canceling on each of the microphones separately or on each of the microphone
`echo canceling on each ofthe microphones separately or on each of the microphone
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`combinations (the combinations of microphones could be infinite). However, the increase in the
`combinations (the combinations of microphones could be infinite). However, the increase in the
`computation load required to perform numerous echo-canceling systems concurrently on each of
`computation load required to perform numerous echo-canceling systems concurrently on each of
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`~t1
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`the microphones or allowable beams is not realistic.
`the microphones or allowable beams is not realistic.
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`An efficient echo-canceling system is needed which will reduce the echo
`An efficient echo-canceling system is needed which will reduce the echo
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`~Jj
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`drastically. However, because of the large dynamic ranges required by the microphone to be able
`drastically. However, because of the large dynamic ranges required by the microphone to be able
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`to pick up very low voices, the microphone will most likely pick up some of the residual echo as
`to pick up very low voices, the microphone will most likely pick up some of the residual echo as
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`well. The residual echo is most disturbing when no other signal is present but less noticed when
`well. The residual echo is most disturbing when no other signal is present but less noticed when
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`a full duplex discussion is taking place.
`a full duplex discussion is taking place.
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`Another problem typical to multluser conferencing systems is that the
`Another problem typical to multi-user conferencing systems is that the
`background noise from several systems is transmitted to all the participating systems and it is
`background noise from several systems is transmitted to all the participating systems and it is
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`preferred that this noise be reduced to a minimum. The beam forming process reduces the
`preferred that this noise be reduced to a minimum. The beam forming process reduces the
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`background noise but not enough to account for the plurality of systems'
`background noise but not enough to account for the plurality of systems.
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`OBJECTS AND SUMMARY OF THE INVENTION
`OBJECTS AND SUMMARY OF THE INVENTION
`
`It is therefore an object of the invention to provide an interference canceling
`It is therefore an object of the invention to provide an interference canceling
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`system.
`system.
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`lt is another object of the invention to provide an interference canceling system to
`It is another object of the invention to provide an interference canceling system to
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`cancel interference while providing full duplex communication.
`cancel interference while providing full duplex communication.
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`It is yet another object ofthe invention to provide an interference canceling
`It is yet another object of the invention to provide an interference canceling
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`3---
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`system to cancel an echo present in a teleconference'
`system to cancel an echo present in a teleconference.
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`It is stilt another object of the present invention to provide an interference
`It is still another object of the present invention to provide an interference
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`tii
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`canceling system to cancel an echo present in video teleconferencing'
`canceling system to cancel an echo present in video teleconferencing.
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`It is further an object of the invention to allow a steerable directional audio beam
`It is further an object of the invention to allow a steerable directional audio beam
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`to function with the interference canceling system of the present invention'
`to function with the interference canceling system of the present invention.
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`It is yet a further object of the invention to overcome background noise in the
`It is yet a further object of the invention to overcome background noise in the
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`conferencing system and reduce the residual echo to a minimum.
`conferencing system and reduce the residual echo to a minimum.
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`ln accordance with the foregoing objectives, the present invention provides an
`In accordance with the foregoing objectives, the present invention provides an
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`interference canceling system, method and apparatus for canceling, from a target signal generated
`interference canceling system, method and apparatus for canceling, from a target signal generated
`from a target source, an interference signal generated by an interference source' A main input
`from a target source, an interference signal generated by an interference source. A main input
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`inputs the target signal generated by the talget source. A reference input inputs the interference
`inputs the target signal generated by the target source. A reference input inputs the interference
`signal generated by the interference source. A beam splitter beam-splits the target signal into a
`signal generated by the interference source. A beam splitter beam-splits the target signal int