a2) United States Patent
`US 6,341,123 B1
`(0) Patent No.:
`Tsujishita et al.
`Jan. 22, 2002
`(45) Date of Patent:
`
`US006341123B1
`
`(54)
`
`(75)
`
`DIGITAL AUDIO BROADCASTING
`RECEIVER
`
`Inventors: Masahiro Tsujishita; Masayuki
`Ishida; Kenichi Taura; Tadatoshi
`Ohkubo; Masakazu Morita, all of
`Tokyo (JP)
`
`(73) Assignee:
`
`Mitsubishi Denki Kabushiki Kaisha,
`Tokyo (JP)
`
`(*) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`Appl. No.: 09/015,768
`
`Filed:
`
`Jan. 29, 1998
`
`(30)
`Foreign Application Priority Data
`sssssecceee F-O1B592
`Jan. 31, 1997
`
`(51)
`(52)
`(58)
`
`(56)
`
`Wn OUosssasscrinssexanssngeasniguraicansisteny HO4L 27/06
`
`US. Ch.
`oo. eeececeeeteeeeeee 370/210; 375/340; 375/344
`Field of Search.
`.......0::cc6cccccsscsees00, 370/203, 210,
`370/350, 503, 516; 375/316, 324, 329,
`330, 340, 341, 344
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,228,025 A
`5,282,222 A *
`
`7/1993 Le Floch et al.
`1/1994 Fattouche et al.
`
`.....
`....
`
`wees 370/20
`sever 375/260
`
`5,550,812 A *
`5,787,123 A *
`$,812,523 A *
`
`8/1996 Philips 1.00.00... 370/203
`
`...
`. 375/324
`7/1998 Okada etal.
`9/1998 Isaksson et al... 370/208
`FOREIGN PATENT DOCUMENTS
`
`EP
`FR
`wo
`
`0656706 A2
`2721778
`WO95 20848
`
`6/1995
`12/1995
`8/1995
`
`OTHER PUBLICATIONS
`
`“A Digital Audio Broadcasting (DAB) Receiver”, K. Taura,
`et al., IEEE Transactions on Consumer Electronics, U.S.
`IEEE Ine. vol. No. 3, Aug. 1996, pp. 322-326.
`
`* cited by examiner
`
`Primary Examiner—Chau Nguyen
`Assistant Examiner—Jasper Kwoh
`
`(57)
`
`ABSTRACT
`
`A digital audio broadcasting receiver comprises a phase
`error detector for detecting a phase error from data from a
`differential demodulator, an average value processing unit
`for determining the average value ofphase errors, a memory
`for storing the phase errors ofthe carriers outputted from the
`phase error detector, and a phase error correcting unit which
`excludes a phase error whose sign is opposite to that ofthe
`average value among the phase errors stored in the memory,
`and determined the average value of phase errors again,
`thereby making it possible to obtain a phase error signal
`which is less affected by leakage from other carriers.
`
`7 Claims, 19 Drawing Sheets
`
`
`
`
`Le ee
`
`PHASE ERROR j
`26
`CORRECTION j
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 1
`
` SIGN
`DETERMINATION
`
`|23a
`
`|||
`
`8
`
`13
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 1
`
`

`

`7ale|||eee;
`
`gowadgowsd
`ASWHd©92
`NOLLVNIWY3130
`NOILOSLSG
`ONIDWHIAY72
`
`PNOWOZHHOO00a|YOUHS
`
`YOuuS
`
`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 1 of 19
`
`US 6,341,123 B1
`
`(
`
`ras
`
`dNVHALYSANO9GelOa=f88h
`SlvkLhOlZ9S€
`
`IGYSLIATWLLN3Y33310XI
`NOIS
`ASVHd
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 2
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 2
`
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 2 of 19
`
`US 6,341,123 B1
`
`FIG. 2
`
`
`
`
`6 ave’ — 0
`100
`i+ 0
`
`n+-0
`
`
` ARE
`
`SIGNS OF @ ave AND @i THE
`SAME?
`
`6 ave + Bave'+ Gi
`
`n-n+1
`
`
`YES
`
`104
`
`END OF DATA?
`
`
`
`@ ave : AVERAGE VALUE OF PHASE ERRORS
`6 ave'
`: CORRECTION VALUE FOR THE AVERAGE VALUE OF PHASE ERRORS
`@;
`: PHASE ERROR IN ANi-TH CARRIER
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 3
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 3
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 3 of 19
`
`US 6,341,123 Bl
`
`FIG. 3
`
`e : CORRECTED
`x : UNCORRECTED
`
`
`
`
`
`PHASEERROR(DEGREES)
`
`-100
`
`-50
`
`0
`
`50
`
`100
`
`FREQUENCY DEVIATION (Hz)
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 4
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 4
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 4 of 19
`
`US 6,341,123 B1
`
`Bl
`
`Li
`
`wTdAVYHALYAANOO9}
`
`o1lanyvd
`
`
`
`GowsaGowsa
`
`SlviLhOLZ9gS
`ayaa]TwiNawassia7|207XIW
` NOILOSL3I0
`0344
`
`
`
`
`
`YOuNSSSVHd
`
`NOILVHYOLSSY
`
`ASWHd
`
`YOUYS
`
`NOILVNIWGS1350
`
`NSIS
`
`ONINAL
`
`TOULNOD
`
`El
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 5
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 5
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 5 of 19
`
`US 6,341,123 B1
`
`FIG. 5
`
`
`
`
`
`
`
`
`
`
`SIGNS OF @ ave AND 61 THE
`SAME?
`
`106
`
`IS THE SIGN OF 61
`PLUS?
`
`6 ave’ +— Oave't+ Oi
`
`isi+1
`
`103
`
`END OF DATA?
`
`YES
`
`6 ave : AVERAGE VALUE OF PHASE ERRORS
`@ ave’ : CORRECTION VALUE FOR THE AVERAGE VALUE OF PHASE ERRORS
`@;
`: PHASE ERRORIN AN i-TH CARRIER
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 6
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 6
`
`

`

`Jan. 22, 2002
`
`Sheet 6 of 19
`
`US 6,341,123 B1
`
`AYVNIDVWI
`
`
`
`
`
`0¢NOISLHWdONINAL
`
`8l
`
`
`
`
`
`gowadgow3adWV
`
`U.S. Patent
`
`SIvi
`
`
`
`IGY3LIAWILN3Y3510dl
`
`9‘Ola
`
`
`
`PLdNVY3LYSANO99}6ZNOILV.LOYolyTOXLNODNOILO3150
`
`
`
`
`olanywdASVHdONASONAS
`
`0344
`
`NOILVNIWHaL30}+E
`
`CO)
`
`||3O/ve|seC)||
`
`o¢-[ESOIN]
`
`el
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 7
`
`TOYLNOO
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 7
`
`
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 7 of 19
`
`US 6,341,123 B1
`
`FIG. 7
`
`IMAGINARY PARTS
`<0?
`
`
`
`
`
`Imp + Imp + Imi
`
`
`Rep + Rep + Rei
`Rem «— Rem + Rei
`
`Imm <— Imm + Imi
`
`
`
`
`
`
`END OF DATA?
`
`206
`
`ABS ee)> ABS(Imp)
`
`207
`
`
`
`6 ave «— Imm/Rem
`
`8 ave + Imp/Rep
`
`Imm_: SUM OF MINUS IMAGINARY PARTS
`Imp
`:SUM OF PLUS IMAGINARY PARTS
`Rem : SUM OF REAL PARTS WHEN IMAGINARY PARTS ARE MINUS
`Rep : SUM OF REAL PARTS WHEN IMAGINARY PARTS ARE PLUS
`Imi
`: IMAGINARY PARTS AFTER PHASE ROTATION
`Rei
`: REAL PARTS AFTER PHASE ROTATION
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 8
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 8
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 8 of 19
`
`US 6,341,123 B1
`
`8k
`
`St
`
`vl
`
`
`
`gowaddgowad
`
`
`
`\GHSLIAWILN3Y33510
`
`dl
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`3SVHd
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`
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`
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`
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`
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`
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`
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`ve
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`
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`
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`
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`
`O34
`
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`
`TOYULNOD
`
`el
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 9
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 9
`
`
`
`
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 9 of 19
`
`US 6,341,123 B1
`
`FIG. 9
`
`200
`
`
`
`Imm + Imm + Imi
`
`Rem «— Rem + Rei
`
`205
`
`END OF DATA?
`
`IMAGINARY PARTS <0
`
`?
`
`202
`
`no
`
`
`
`
`
`Imp «— Imp + Imi
`Rep + Rep+ Rei
`
`YES
`
`206
`
`@ avep + Imp/Rep
`8 avem + Imm/Rem
`
`207
`
`NO
`
`ABS(Imp) < ABS (Imm)
`
`9
`
`6 avep= 6 avep - 1/2
`
` YES
`
` 213
`
`G avem = 6 avem + 1/2
`
`214
`
`6 ave = ( 8 avep + O avem) /2
`
`Imm :SUM OF MINUS IMAGINARY PARTS
`Imp
`:SUM OF PLUS IMAGINARY PARTS
`Rem :SUM OF REAL PARTS WHENIMAGINARY PARTS ARE MINUS
`Rep
`:SUM OF REAL PARTS WHENIMAGINARY PARTS ARE PLUS
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 10
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 10
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 10 of 19
`
`US 6,341,123 B1
`
`8I
`
`aadVYALYAANOO
`olanvv/a
`
`ZIOt
`
`YOWHS-3SVHd
`
`ANTWASDVYSAV
`
`NOILO3L30
`
`ONAS
`
`ONAS
`
`TOULNOD
`NOLLO3L30
`
`6
`
`8
`
`Slvi
`
`Lt
`
`Ol
`
`gowad
`
`QOWw3a
`
`\GYSLiA
`WILN3Y35510
`
`QOWwsG
`
`ov
`
`LINANOdWO9
`
`NOILVNIWY3130
`
`A9VAVAT
`
`
`
`YOHYSSSVHd
`
`NOILOSHHOOD
`
`el
`
`OLOld
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 11
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 11
`
`
`
`
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 11 of 19
`
`US 6,341,123 B1
`
`FIG. 11
`
`
`300
`
`IS LEAKAGE
`NO
`FROM OTHER CARRIERS
`
`LARGE?
`
`
`
`301
`
`
`
`O ave +- 3xX8p/2- 6 ae/l2
`
`
`
`
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 12
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 12
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 12 of 19
`
`US 6,341,123 B1
`
`LI
`
`9}
`
`NOILO3130
`
`6
`
`8
`
`4
`
`NOILVIEWA
`
`NOILO3L40
`
`
`
`
`
`YHOHHSASVHd
`
`NOLLOSYHOO
`
`9€¢
`
`el
`
`8I
`
`dNVOs
`YH3LYSANO9
`
`vid
`
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`YOUYS-SSVHd
`h
`TOXLNOO
`NOILO3L30
`
`2w
`
`ONAS
`
`ONAS
`
`Sh
`
`vb
`
`Lh
`
`GOWw3d
`
`dgowsa
`
`IGY3LIA
`WILN3Y33310
`
`an
`
`clOl
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 13
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 13
`
`
`
`
`
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 13 of 19
`
`US 6,341,123 B1
`
`FIG. 13
`
`302
`
`
`
` IS VARIATION o
`
`OF PHASE ERROR GREATER
`THAN A SET VALUE
`
`6 ave - 3X0p/2- 6 ave/2
`
`
`301
`
`: VARIATION OF PHASE ERROR
`co
`8 ave : AVERAGE VALUE OF PHASE ERRORS
`6» : MAXIMUM VALUE OF PHASE ERROR
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 14
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 14
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 14 of 19
`
`US 6,341,123 B1
`
`Zi9h
`
`olagnyvid
`
`dVY3LYSANOD
`
`NOLLYNINYS130
`NOILOSYYOO
`
`NOLLVNITONI
`HOSSSVHd
`
`IGY3LIA
`
`gowsd
`
`gowsa
`
`YOWHS-ASWHd
`
`
`
`ANTWAJDVYESAV
`
`NOILOSL30
`
`WILN3834310 ylOld
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 15
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 15
`
`
`
`
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 15 of 19
`
`US 6,341,123 B1
`
`FIG. 15
`
`ASB ( 6 n) > ABS ( 8b)
`
`
`9
`
`
`
`
`301
`
`@ ave + 3X0 p/2- 6 ave/2
`
`6 ave : AVERAGE VALUE OF PHASE ERRORS
`6» : MAXIMUM VALUE OF PHASE ERROR
`6n : AVERAGE VALUE OF CURRENT PHASE ERRORS
`@»
`: AVERAGE VALUE OF PREVIOUS PHASE ERRORS
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 16
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 16
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 16 of 19
`
`US 6,341,123 B1
`
`8
`
`pedWVYALYSANOO
`olanyv/a
`ONAS
`
`St
`
`vk
`
`Lh
`
`9}‘Old
`
`gGowsd
`
`\adSLiA
`WLLN3Y33510
`
`raQI
`
`6
`
`8
`
`ra
`
`
`
`HOUYSSSVHd
`
`NOILO3130
`
`
`
`l
`
`ONAS
`
`TOYULNOD
`NOILOSL30
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 17
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 17
`
`
`
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 17 of 19
`
`US 6,341,123 B1
`
`FIG. 17
`
`OFDM DEMODULATION BY DFT
`(WITHOUT FREQUENCYDEVIATION)
`
`n-TH OUTPUT PASS
`
`CARRIER WAVES
`
`INPUT SIGNAL TO DFT
`
`CHARACTERISTIC
`
`FREQUENCY
`
`FREQUENCY
`
`
`
`n-TH OUTPUT SIGNAL
`FROM DFT
`
`FIG. 18
`
`OFDM DEMODULATION BY DFT
`(WITHOUT FREQUENCY DEVIATION)
`
`n-TH OUTPUT PASS
`CHARACTERISTIC
`
`CARRIER WAVES
`
`INPUT SIGNAL TO DFT
`
`
`n-3 n-2 n-1 n n+1 n+2
`
`n-TH OUTPUT SIGNAL
`FROM DFT
`
`FREQUENCY
`
`FREQUENCY
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 18
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 18
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 18 of 19
`
`US 6,341,123 B1
`
`FIG. 19
`
`CALCULATED VALUES OF DIFFERENTIALLY DEMODULATED DATA
`(FREQUENCY DEVIATIONIS -80Hz)
`
`PARTS
`
` IMAGINARY
`
`REAL PART
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 19
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 19
`
`

`

`U.S. Patent
`
`Jan. 22, 2002
`
`Sheet 19 of 19
`
`US 6,341,123 B1
`
`FIG. 20
`
`CALCULATED VALUES OF PHASE ERROR WITH RESPECT TO
`FREQUENCY WHEN THEREIS LEAKAGE FROM OTHER CARRIERS
`
`
`
`SEE
`AVOINUEEETE
`
`VANLEEE
`
`
`ALUNEE
`TUTTENEE
`
`
`TTTNTL
`
`
`TTTNA
`
`
`AE-100
`
`
`
`50
`
`100
`
`
`
`
`
`PHASEERROR(DEGREES)
`
`So
`
`-50
`
`FREQUENCY DEVIATION (Hz)
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 20
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 20
`
`

`

`US 6,341,123 Bl
`
`1
`DIGITAL AUDIO BROADCASTING
`RECEIVER
`
`BACKGROUND OF THE INVENTION
`
`The present inventionrelates to a digital audio broadcast-
`ing receiver in which each carrier is subjected to differential
`phase modulation and orthogonal frequency division multi-
`plexing (OFDM).
`As a system which permits transmission ofdigital data to
`a mobile object which is strongly affected by the problems
`of radio wave propagation, such as the multipath and fading,
`the orthogonal frequency division multiplexing (OFDM)
`transmission system is known, and the use of this system in
`broadcasting is under way. Its typical example is seen in
`digital audio broadcasting (DAB) which is set
`forth in
`ITU-R Recommendation BS.774.
`
`FIG. 16 is a block diagram ofa digital audio broadcasting
`receiver.
`
`In the drawing, reference numeral 1 denotes an antenna;
`2, an RF amplifier; 3, a frequency converter (MIX); 4, a local
`oscillator (LO), 5, an intermediate frequency amplifier (IF
`AMP);6, an orthogonal demodulator (DEMOD);7, an A/D
`converter; 8, a synchronizing signal detector (synchronous
`detection); 9, a synchronization control means; 10, a com-
`plex discrete Fourier
`transform processing (hereafter
`referred to as “DFT”) means; L1, a differential demodulator;
`12, a phase error detector, 13, a frequency tuning control
`means; 14, a Viterbi decoder; 15, an MPEG audio decoder;
`16, a D/A converter; 17, an audio amplifier; and 18, a
`speaker.
`In the receiver configured as described above, the broad-
`cast wave received by the antenna 1 is amplified by the RF
`amplifier 2,
`is subjected to frequency conversion by the
`frequency converter 3, is subjected to removal of unwanted
`components such as adjacent channel waves and amplifica-
`tion by the intermediate frequency amplifier 5, is subjected
`to detection by the orthogonal demodulator 6, and is
`imparted to the A/D converter 7 as a baseband signal.
`The signal sampled by the A/D converter 7 is subjected to
`DFT by the DFT means 10, and the phase of each trans-
`mission carrier subjected to quadrature phase shift keying
`(QPSK)is detected. In the ensuing differential demodulator
`11, modulated phases of the same carrier oftwotransmitted
`symbols which are limewise adjacent
`to each other are
`compared, and processing (differential demodulation) for
`outputting a phase shift in the mean time is effected. The
`data subjected to differential demodulation is then outputted
`to the Viterbi decoder 14 in accordance with a rule on the
`order ofcarriers used in modulation on the transmitting side.
`In the Viterbi decoder 14, interleaving is canceled during
`the time spanning over the range ofa plurality of symbols
`transmitted by the transmitting side,
`the data transmitted
`through convolutional coding is decoded, and correction of
`errors of data occurring on the transmission path is effected
`at that time.
`
`In accordance with the provisions of the layer-2 of ISO/
`MPEGI,
`the MPEG audio decoder 15 expands the com-
`pressed DAB broadcast audio data outputted from the Vit-
`erbi decoder 14, and sends the sameto the D/A converter 16.
`The audio signal subjected to analog conversion by the D/A
`converter 16 is reproduced by the speaker 18 via the
`amplifier 17.
`Here, the synchronizing signal detector 8 detects the null
`symbol (the period during which no signal is present) by
`envelope detection, in the frame alignment signal included
`
`20
`
`todwn
`
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`in the transmitted signal of DAB. This output serves as a
`timing signal by which DFT effected by the DFT means 10
`through the synchronization control means 9 is executed
`correctly in synchronism with the transmission frame and
`each symbolofthe signal.
`The phase error detector 12 detects an error between an
`original phase point and the phase data of each carrier
`outputted from the differential demodulator 11. Thatis, in
`DAB,if the frequency ofthe signal imparted to the orthogo-
`nal demodulator 6 is correcl, the phase of the differentially
`demodulated data outputted from the differential demodu-
`lator LL in correspondence with each carrier becomes sub-
`stantially one of 7/4, 3-1/4, 5-2/4, and 7-m/4.
`Accordingly, if the data corresponding to each carrier is
`multiplied by 4 and the remainder is obtained with respect
`to 2x, this value becomes = if there is noerror in the original
`data, and becomes a multiple of 4 of that value if there is a
`phase errorin the original data, so that phase error detection
`is carried out. In practice, in the phase error detector 12, the
`aforementioned operation is performed with respect to the
`data of the multiplicity of carriers, and the accuracy of
`detection is improved by averaging the results.
`Since the phase error €
`thus determined is an output from
`the differential demodulator Ll,
`the relationship of the
`following Formula (1) holds between an error € of the signal
`frequency at this time and the phase errore:
`t=e/T
`
`(1)
`
`Here, T is a symbol period including a guard interval.
`The frequency tuning control means 13 operates in such
`a manner as to cause the frequency error C of the baseband
`signal
`imparted from the orthogonal demodulator 6 to
`approach 0 by controlling the frequency ofthe intermediate
`frequency signal outputted from the frequency converter 3
`by controlling the frequencyof the local oscillator 4 in such
`a manner that this phase error € becomes small.
`As already described, the DABsignal is comprised of a
`multiplicity ofcarriers. To separate the carriers, DFT has an
`output characteristic shown in FIG. 17, and when the
`frequency is pulled in correctly, components from other
`carriers do not leak,
`However, when the frequency is not pulled in correctly,
`components from other carriers leak, as shown in FIG, 18.
`Here, if there is no leakage from other carriers even if
`there is a frequency deviation, adjacent carriers sland s2can
`be expressed by the following Formula (2):
`
`sl=exp{j(2(f0+Af-n-fec)t}
`
`s2=exp{j(2a(f0+Af-n-fec)
`
`(t+tsym)+Oc+0n)}
`
`where, f0: transmission frequency
`Af: frequency deviation
`n: carrier number
`
`(2)
`
`fcc: interval between carrier frequencies
`tsym: the period of one symbol
`On: (2N+1)p/4, N is an arbitrary integer
`Oc: 2n(f0-n-fec)-tsym
`Accordingly,
`the phase error from (2-.N+1)m/4 of the
`same carrier of adjacent symbols can be expressed by the
`following Formula (3):
`
`O=Aftsym
`
`(3)
`
`Hence, it can be seen that the phase error is proportional to
`the frequency deviation.
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 21
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 21
`
`

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`US 6,341,123 Bl
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`3
`In practice, however, when the frequency has deviated, if
`there is leakage from other carriers, ¢.g., a frequency of -80
`Hz,
`large variations appear in the differential modulated
`data, as shown in FIG. 19. Here, the differentially demodu-
`lated data is divided into four quadrants of 0-2/2, 2/2-n,
`m—3n/2, and 3n/2—27, but there occurs data which enters
`adjacent quadrants as shown in FIG. 19, andthe sign ofthe
`data which shifted to adjacent quadrants becomes opposite
`and such data constitutes a large phase error. Since errone-
`ous data in which the sign of phase error 1s opposite is also
`used in averaging processing by the phase error detector, the
`detected phase error assumes a value smaller than a real
`value.
`In addition, the greater the deviation ofthe frequency, the
`greater the leakage of components from other carriers, so
`that the variation becomes larger, and the data is located
`closer to the adjacent quadrants, with the result
`that
`the
`aforementionederror is liable to occur. For this reason, as for
`the frequency deviation and the average value of phase
`errors,
`the phase error becomes small starting from the
`frequency deviation of 70 Hz or thereabouts, where the
`frequency deviation and the average phase error cease to be
`proportional. For this reason, if the frequency deviation is
`large, there has been a problem in that it takes time in the
`pulling in of the frequency.
`
`SUMMARYOF THE INVENTION
`
`The present invention has been devised to overcome the
`above-described problem, and its object is to obtain a digital
`audio broadcasting receiver which is provided with a fre-
`quency control means for a local oscillator which is not
`affected by variations in the phase error due to the frequency
`deviation.
`
`In the digital audio broadcasting receiver in accordance
`with the present invention, a DABsignal inputted from the
`antenna is subjected to OFDM demodulation by the DFT,
`the phase difference between twosuccessive symbols on the
`same carrier is calculated by the differential demodulator,
`the deviation of the differentially demodulated data in an
`N-th quadrant from a (2N-1)m/4 radian is detected as the
`phase difference by the phase error detector, the phase errors
`of the carriers are averaged by the average value processing
`unit, the sign of the phase errors is detected by the sign
`determining unit, the phase error is corrected by excluding
`the effect of data which changed to an adjacent carrier by the
`phase error correcting unit in correspondence with the result
`of determination by the sign determining unit, and the
`frequency of the local oscillator is controlled by the cor-
`rected phase error.
`In the digital audio broadcasting receiver in accordance
`with the present invention, a DAB signal inputted from the
`antenna is subjected to OFDM demodulation by the DFT,
`the phase difference between two successive symbols on the
`same carrier is calculated by the differential demodulator,
`the deviation of the differentially demodulated data in an
`N-th quadrant from a (2N-1)z/4 radian is detected as the
`phase difference by the phase error detector, the phase errors
`of the carriers are averaged by the average value processing
`unit, the sign of the phase errors is detected by the sign
`determining unit, and the frequency of the local oscillator is
`controlled by restoring the data which changed to an adja-
`cent carrier by the phase error correcting unit in correspon-
`dence with the result of determination by the sign determin-
`Ing unit.
`In addition, a DAB signal inputted from the antenna is
`subjected to OFDM demodulation by the DFT, the phase lo
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`difference between two successive symbols on the same
`carrier is calculated by the differential demodulator, a phase
`rotation by a (2N-1)7/4 radian is imparted to the differen-
`tially demodulated data in an N-th quadrant by the phase
`rotating unit, the sign of imaginary parts of the data after the
`phase rotation is determined by the imaginary-part sign
`determining unit, addition is effected with respectto only the
`data whose signs of the imaginary parts are the same, the
`phase error detecting unit detects the phase error by exclud-
`ing the effect of data which changed to an adjacent carrier,
`and the frequency of the local oscillator is controlled.
`In addition, a DAB signal inputted from the antenna is
`subjected to OFDM demodulation by the DFT, the phase
`difference between two successive symbols on the same
`carrier is calculated by the differential demodulator, a phase
`rotation by a (2N-1)7/4 radian is imparted to the differen-
`tially demodulated data in an N-th quadrant by the phase
`rotating unit, the sign of imaginary parts of the data after the
`phase rotation is determined by the imaginary-part sign
`determining unit, addition is effected with respect to only the
`data whose signs of the imaginary parts are the same, the
`effect of data which changed to an adjacent carrier is
`restored by the phase error detecting unit, and the frequency
`of the local oscillator is controlled.
`
`In addition, a DAB signal inputted from the antenna is
`subjected to OFDM demodulation by the DFT, the phase
`difference between two successive symbols on the same
`carrier is calculated by the differential demodulator,
`the
`deviation of the differentially demodulated data in an N-th
`quadrant from a (2N-1)z/4 radian is detected as the phase
`difference by the phase error detector, the phase errors of the
`carriers are averaged by the average value processing unit,
`the relative magnitude of leakage from another carrier is
`determined on the basis of output data from the differential
`demodulator, the average value of phase errors is corrected
`by the phase error correcting unit if the leakage from another
`carrier is large, and the frequency ofthe local oscillator is
`controlled.
`
`In addition, a DAB signal inputted from the antenna is
`subjected to OFDM demodulation by the DFT, the phase
`difference between two successive symbols on the same
`carrier is calculated by the differential demodulator,
`the
`deviation of the differentially demodulated data in an N-th
`quadrant from a (2N-1)z/4 radian is detected as the phase
`difference by the phase error detector, the phase errors of the
`carriers are averaged by the average value processing unil,
`the variation of the differentially demodulated data is
`detected by the variation determining unit, the average value
`of phase errors is corrected if the variation is large, and the
`frequency of the local oscillator is controlled.
`In addition, a DAB signal inputted from the antenna is
`subjected to OFDM demodulation by the DFT, the phase
`difference between two successive symbols on the same
`carrier is calculated by the differential demodulator,
`the
`deviation of the differentially demodulated data in an N-th
`quadrant from a (2N-1)z/4 radian is detected as the phase
`difference by the phase error detector, the phase errors ofthe
`carriers are averaged by the average value processing unit,
`an inclination of the magnitude of the phase error is detected
`by the inclination detecting unit, the average value of phase
`errors is corrected if the inclination is not in a converging
`direction, and the frequency of the local oscillator is con-
`trolled by the corrected phase error.
`In the digital audio broadcasting receiver in accordance
`with the present invention, the phase error correcting unit
`handles the phase error whosesignis different from the sign
`Petitioner Sirius XM Radio Inc. - Ex 1002, p. 22
`
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 22
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`US 6,341,123 Bl
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`5
`of the average value of phase errors as being data in an
`adjacent quadrant since the phase difference in the differ-
`entially demodulated data has exceeded +m/2, and deter-
`mines that the data is erroneous. Hence, the phase error
`correcting unit corrects the phase error by effecting averag-
`ing with respect to only the phase errors whose sign agrees
`with the sign of the average value of phase errors.
`In addition, in the digital audio broadcasting receiver in
`accordance with the present invention, in the restoration of
`the phase error by the phase error correcting unit, if the sign
`of the phase error is different from the that of the average
`value,
`the phase error is considered as being data in an
`adjacent quadrant since the phase difference in the differ-
`entially demodulated data has exceeded +7/2. If the phase
`error is assumed to be q,
`the phase error correcting unit
`effects correction of 6-1/2 if the phase error is plus, and
`6+z/2 if the phase error is minus.
`In addition, in the digital audio broadcasting receiver in
`accordance with the present invention, if the absolute value
`is smaller between the absolute value of the sum of plus
`imaginary parts and the absolute value of the sum of minus
`imaginary parts, the phase error is +/2 or more, so that such
`data is handled as being data in an adjacent quadrant. Hence,
`since it is considered that the sign has been erroneous, the
`phase error correcting unit calculates imaginary parts/real
`parts of only the data whose absolute value is greater, and
`outputs the same as the phase error.
`In addition,in the digital audio broadcasting receiver in
`accordance with the present
`invention,
`the phase error
`correcting unit calculates imaginary parts/real parts for plus
`imaginary parts and imaginary parts/real parts for minus
`imaginary parts, and the data which exhibits a greater
`absolute value between plus imaginary parts and minus
`imaginary parts is left as it is and is set as a phase error 1.
`Meanwhile,
`in the case of data which exhibits a smaller
`absolute value is handled as data in an adjacent quadrant
`since the phase error has exceeded +7/2,and it is considered
`that the sign of such data has been erroneous. Accordingly,
`if
`the phase error is assumed to be gq,
`the phase error
`correcting unit effects correction of +-7/2 if the imaginary
`parts are plus, and 6+4:/2 if the imaginary parts are minus,
`thereby restoring the phase error to an original phase error
`as a phase error 2, An average ofthe phase error 1 and the
`phase error 2 is used as the phase error.
`In addition, in the digital audio broadcasting receiver in
`accordance with the present invention, if the leakage from
`another carrier becomes large,
`the phase error becomes
`smaller than a real value due to the leakage from another
`carrier, so that
`the phase error correcting unit provides
`processing for increasing the phase error, for example.
`In addition, in the digital audio broadcasting receiver in
`accordance with the present invention, the greater the fre-
`quency deviation, the more the leakage from another carrier
`increases in the result of DFT, and the phase is also affected.
`The effect becomes large when the phase difference with
`respect
`to a neighboring carrier is +7/2, but
`the phase
`difference with a neighboringcarrier is not uniform. For this
`reason,
`the leakage from other carriers also changes.
`Therefore, variations occurin the result of differential modu-
`lation as shown in FIG. 19. The greater the leakage from
`other carriers, the larger the variations, so that the variation
`of the data is calculated by the phase error correcting unit to
`determine the relative magnitude of leakage from other
`carriers.
`
`In addition, in the digital audio broadcasting receiver in
`accordance with the present invention, the leakage compo-
`
`6
`nent makesuse of the fact that, between the region where the
`leakage from another carrier is large and the region where it
`is small, the signs of inclination of phase errors with respect
`to the frequency deviation are opposite. First, since feedback
`is provided to the local oscillator in such a manner that the
`phase difference approaches 0, the magnitude of the phase
`difference becomes small in the region where the leakage
`from other carriers is small, However, in the region where
`the frequency leakage is large, even if the phase error is
`small, the effect of leakage components from other carriers
`becomes small and the phase error approaches a real phase
`error, so that
`the phase error becomes apparently large.
`Accordingly, the leakage from other carriers is detected by
`performing a calculation in accordance with the following
`formula:
`
`10
`
`15
`
`AO= (absolute value of the average value of current phase
`errors)—(absolute value of the average value of previ-
`ous phase errors) If the sign of the previous errors and
`the sign of the current phase errors are the same, it is
`considered that the real phase error is approaching 0. As
`a result, if AO is plus, it can be determined that the
`phase error is becoming smaller than the real value due
`to the leakage from other carriers.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIG. 1 is a block diagram illustrating the configuration of
`a digital audio broadcasting receiver in accordance with a
`first embodiment of the present invention;
`FIG. 2 is a flowchart of processing by a phase error
`correcting section in accordance with the first embodiment;
`FIG. 3 is a diagram illustrating the results of measurement
`of the phase error with respect to the frequency deviation in
`accordance with the first embodiment;
`FIG. 4 is a block diagram illustrating the configuration of
`the digital audio broadcasting receiver in accordance with a
`second embodiment of the present invention;
`FIG. 5 is a flowchart of processing by a phase error
`correcting section in accordance with the second embodi-
`ment;
`FIG. 6 is a block diagram illustrating the configuration of
`the digital audio broadcasting receiver in accordance with a
`third embodiment of the present invention;
`FIG, 7 is a flowchart of processing by a phase error
`correcting section in accordance with the third embodiment;
`FIG. 8 is a block diagram illustrating the configuration of
`the digital audio broadcasting receiver in accordance with a
`fourth embodimentof the present invention;
`FIG. 9 is a Howchart of processing by a phase error
`correcting section in accordance with the fourth embodi-
`ment;
`FIG, 10 is a block diagram illustrating the configuration
`ofthe digital audio broadcasting receiver in accordance with
`a fifth embodiment of the present invention;
`FIG. 11 is a flowchart of processing by a leakage com-
`ponent determining unit and a phase error correcting section
`in accordance with the fifth embodiment;
`FIG. 12 is a block diagram illustrating the configuration
`of the digital audio broadcasting receiver in accordance with
`a sixth embodiment of the present invention;
`FIG. 13 is a flowchart of processing by a leakage com-
`ponent determining unit and a phase error correcting section
`in accordance with the sixth embodiment;
`FIG. 14 is a block diagram illustrating the configuration
`ofthe digital audio broadcasting receiver in accordance with
`a seventh embodiment of the present invention;
`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 23
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`Petitioner Sirius XM Radio Inc. - Ex. 1002, p. 23
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`

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`US 6,341,123 Bl
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`7
`FIG. 15 is a flowchart of processing by an inclination
`determining unit and a phase error correcting section in
`accordance with the seventh embodiment;
`FIG. 16 is a block diagram illustrating a conventional
`digital audio broadcasting receiver;
`FIG. 17 is a conceptual diagram of DFTin a case where
`there is no frequency deviation;
`FIG. 18 is a conceptual diagram of DFTin a case where
`there is a frequency deviation;
`FIG. 19 is a diagram illustrating calculated values of
`differentially demodulated data owing to leakage from other
`carriers due to a frequency deviation;
`FIG. 20 is a diagram illustrating calculated values of the
`phase error and the frequency deviation due to leakage from
`other carriers.
`
`15
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`a specific description will be given of the
`Hereafter,
`embodiments of the present invention by referring to the
`drawings which illustrate its embodiments.
`First Embodiment
`
`8
`In the phase error correcting section 23a, when the
`average value and the sign determined by the sign deter-
`mining unit 22a are of the same data among the phase e