`
`USOUGMI 12331
`
`(12) United States Patent
`US 6,341,123 B1
`(10) Patent N0.:
`
`
`Tsujishita et al. Jan. 22, 2002 (45} Date of Patent:
`
`(54) DIGITAL AUDIO BROADCASTING
`RECEIVER
`
`(75)
`
`Inventors: Masah'tro Tsujishitn; Masayuki
`Ishida; Kenichi Taura; Tadotoshi
`Ohkuho; Masakazu Morita, all of
`Tokyo (JP)
`
`(73) Assignee: Mitsubishi Denki Kahushiki Kaisha.
`Tokyo (JP)
`
`( *) Notice:
`
`Subject to any disclaimer, the term ofthis
`patent is extended or adjusted under 35
`U.S.C. 154(b) by 0 days.
`
`(2]) Appl. No: 0911115763
`
`(22)
`
`Filed:
`
`Jan. 29, 1998
`
`(3(1)
`
`Foreign Application Priority Date
`
`Jan. 31. rue?
`
`(JP)
`
`94.113592
`
`Int. Cl.7 ................................................ HIML 27i06
`(51)
`.
`.
`(52) US. Cl.
`3701910; 3758-10; 3T5t344
`
`Field of Search
`(58)
`370203. 210.
`370,850, 503. 516; 375.3316. 324. 329.
`330. 340. 341. 344
`
`(56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5228.025 A
`5,282,222 A ‘
`
`131988 [13 l-‘Ioch et al.
`1.31094 Fattouchc ct al.
`
`flit-'20
`STSIZMJ
`
`1
`
`some. Philips
`~
`Tf1998 Okada eta].
`'
`* @1908 [saksson el al.
`
`3700.03
`.. 3755324
`
`.. 370903
`FOREIGN PATENT DOCUMENTS
`
`EP
`FR
`W0
`
`0656706 A}.
`272]??8
`“(09520848
`
`oil 995
`I 2;“ I 9'95
`83'1995
`
`OTHER PUBLICATIONS
`
`“A Digital Audio Broadcasting (DAB) Receiver", K. Taura,
`et al.. IEEE Transactions on Consumer Electronics, U.S.
`IEEE Inc. vol. No. 3, Aug. 1996, pp. 322—326.
`
`“ cited by examiner
`
`Primary Examiner—Chan 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
`difl'erential demodulator. an average value processing unit
`for determining the average value ol‘phase errors. a memory
`for storing the phase errors of the carriers outputted from the
`phase error detector. and a phase error correcting unit which
`excludes a phase error whose sign is opposite to that of the
`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
`
`2
`
`10
`
`8
`
`SYNC
`DETECTION
`
`YNC
`CONTROL
`
`3 S
`
` SIGN
`
`DETERMINATION
`
` lnzaa
`
`i
`l.
`
`||
`
`26
`
`PHASEERHOFI'I
`CORRECTION j
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 1
`
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`L
`
`27
`
`13
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 1
`
`
`
`US. Patent
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 2
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 2
`
`
`
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 2 01'19
`
`US 6,341,123 B1
`
`FIG. 2
`
`
`
` ARE
`SIGNS OF 6 ave AND 9 i THE
`
`SAME?
`
`101
`YES
`
`
`flave'F 0ava'+ I91
`
`n+~n+1
`
`104
`
`END OF DATA?
`
`
`
`0 ave : AVERAGE VALUE OF PHASE ERRORS
`0 ave'
`: CORRECTION VALUE FOR THE AVERAGE VALUE OF PHASE ERRORS
`a i
`: PHASE ERROR IN AN i-TH CARRIER
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 3
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 3
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 3 of 19
`
`US 6,341,123 B1
`
`FIG. 3
`
`o : CORRECTED
`
`x : UNCORRECTED
`
`(DEGREES)
`
`PHASEERROR
`
`-100
`
`-50
`
`0
`
`50
`
`100
`
`FREQUENCY DEVIATION (Hz)
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 4
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 4
`
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 5
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 5
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`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 5 of 19
`
`US 6,341,123 B1
`
`FIG. 5
`
` ARE
`SIGNS OF 6 ave AND 6 1 THE
`SAME?
`
`
`
`105
`
`101
`
`
`
`IS THE SIGN OF 6 I
`
`PLUS?
`
`
` flave'“ aave'+ 3i
`
`i*—i+1
`
`103
`
`END OF DATA?
`
`YES
`
`
`
`6 ave : AVERAGE VALUE OF PHASE ERRORS
`6 ave'
`: CORRECTION VALUE FOR THE AVERAGE VALUE OF PHASE ERRORS
`6i
`: PHASE ERROR IN AN i-TH CARRIER
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 6
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 6
`
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 7
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 7
`
`
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 7 of 19
`
`US 6,341,123 B1
`
`FIG. 7
`
`
`
`IMAGINARY PARTS
`< 0?
`
`“0
`
`YES
`
`Imp *- lmp + Imi
`Imm 4- Imm + Imi
`Fiep ‘— Rep + Fiei
`Hem +— Hem + Rei
`
`
`204
`
`20
`
`
`3
`
`
`205
`
`END OF DATA?
`
`YES
`
`206
`
`NO
`ABS (Imm) > ABS (Imp)
`
`?
`
`
`
` 207
`
`0 ave ‘— Imm/Rem
`
`6 ave F Imp/Rep
`
`Imm : SUM OF MINUS IMAGlNARY 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. 1006, p. 8
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 8
`
`
`
`US. Patent
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 9
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 9
`
`
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 9 of 19
`
`US 6,341,123 B1
`
`FIG. 9
`
` IMAGINARY PARTS < 0
`
`1mm '— lmm + lmi
`
`Fiem *- Rem + Rei
`
`Imp *- Imp + lmi
`
`Rep *— Rep + Rei
`
`
`
`
`205
`
`END OF DATA?
`
`YES
`
`206
`
`3 amp ‘-‘ ImpiRep
`3 avern *- ImmiRem
`
`N0
`
`ABS (Imp) < ABS (Imm)
`?
`
`YES
`
`207
`
`9 avap = i9 avap - m’2
`
`
`
` 213
`
`35mm: flavem+1d2
`
`214
`
`3ava=(6avep+3avem)f2
`
`lmm : SUM OF MINUS IMAGINARY PARTS
`Imp
`: SUM OF PLUS IMAGINARY PARTS
`Rem 2 SUM OF REAL PARTS WHEN IMAGINARY PARTS ARE MiNUS
`Rep
`: SUM OF REAL PARTS WHEN IMAGINARY PARTS ARE PLUS
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 10
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 10
`
`
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 11
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 11
`
`
`
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 11 0f 19
`
`US 6,341,123 B1
`
`FIG. 11
`
` IS LEAKAGE
`NO
`FROM OTHER CARRIERS
`
`
`LARGE?
`
`300
`
`
`
`301
`
`
`
`BaveP3X6p/2-0ave/2
`
`
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 12
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 12
`
`
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`US. Patent
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 13
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 13
`
`
`
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 13 (1le
`
`US 6,341,123 B1
`
`FIG. 13
`
` IS VARIATlON 0'
`OF PHASE ERROR GREATER
`THAN A SET VALUE
`?
`
`302
`
`
`
`
`301
`
`Gavek3X0p/2-9ave/2
`
`: VARlATION OF PHASE ERROR
`a
`6 ave : AVERAGE VALUE OF PHASE ERRORS
`6 p
`: MAXIMUM VALUE OF PHASE ERROR
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 14
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 14
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 14 of 19
`
`US 6,341,123 B1
`
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 15
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 15
`
`
`
`
`
`
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 15 (1le
`
`US 6,341,123 B1
`
`F7Ci.1£3
`
`
`
`ASB(6n)>ABS(6b)
`12
`
`301
`
`
`
`
`
`flaveF3X6p/2-6ave/2
`
`0 ave : AVERAGE VALUE OF PHASE ERRORS
`6 p
`: MAXIMUM VALUE OF PHASE ERROR
`6 n
`: AVERAGE VALUE OF CURRENT PHASE ERRORS
`6 b
`: AVERAGE VALUE OF PREVIOUS PHASE ERRORS
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 16
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 16
`
`
`
`US. Patent
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`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 17
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 17
`
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 17 0f19
`
`US 6,341,123 B1
`
`FIG. 17
`
`OFDM DEMODULATION BY DFT
`(WITHOUT FREQUENCY DEVIATION)
`
`n-TH OUTPUT PASS
`CHARACTERISTIC \
`
`CARRIER WAVES
`
`INPUT SIGNAL TO DFT
`
`
`
`
`
`FREQUENCY
`
`n-TH OUTPUT SIGNAL
`FROM DFT
`
`FREQUENCY
`
`FIG. 18
`
`OFDM DEMODULATION BY DFT
`(WITHOUT FREQUENCY DEVIATION)
`
`n-TH OUTPUT PASS
`CHARACTERISTIC
`
`CARRIER WAVES
`
`INPUT SIGNAL T0 DFT
`
`
`
`
`n-3 n-2 n-1 n n+1 n+2
`
`FREQUENCY
`
`n-TH OUTPUT SIGNAL
`FROM DFI'
`
`FREQUENCY
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 18
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 18
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Shcct18 0f19
`
`US 6,341,123 B1
`
`FIG. 19
`
`CALCULATED VALUES OF DIFFERENTIALLY DEMODULATED DATA
`(FREQUENCY DEVIATION IS -80Hz)
`
` IMAGINAFIY
`
`PARTS
`
`REAL PART
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 19
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 19
`
`
`
`US. Patent
`
`Jan. 22, 2002
`
`Sheet 19 0f19
`
`US 6,341,123 B1
`
`FIG. 20
`
`CALCULATED VALUES OF PHASE ERROR WITH RESPECT TO
`FREQUENCY WHEN THERE IS LEAKAGE FROM OTHER CARRIERS
`
`40
`
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`LI.)
`
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`
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`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 20
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 20
`
`
`
`US 6,341,123 B1
`
`1
`DIGITAL AUDIO BROADCASTING
`RECEIVER
`
`BACKGROUND OF THE INVENTION
`
`The present invention relates to a digital audio broadcast-
`ing receiver in which each carrier is subjected to differential
`phase modulation and orthogonal frequency division multi-
`plexing (OFDM).
`m a system which permits transmission of digital 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
`[TU-R Recommendation BS.'E74.
`
`10
`
`15
`
`FIG. 16 is a block diagram ofa digital audio broadcasting
`receiver.
`
`2
`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 symbol of the 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. That is,
`in
`DAB. ifthe frequency ofthe signal imparted to the orthogo-
`nal demodulator 6 is correct, the phase of the differentially
`demodulated data outputted from the differential demodu-
`lator 11 in correspondence with each carrier becomes sub-
`stantially one of EM, 3‘rrE4. 5'm'4, and 'E'rrE4.
`Accordingly. if the data corresponding to each carrier is
`multiplied by 4 and the remainder is obtained with respect
`to Err. this value becomes 5: if there is no error in the original
`data. and becomes a multiple of 4 of that value if there is a
`phase error in 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 e thus determined is an output from
`the differential demodulator 11,
`the relationship of the
`following Formula (1) holds between an error E of the signal
`frequency at this time and the phase error e:
`E-EET
`
`(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 1:. of the baseband
`signal
`imparted from the orthogonal demodulator 6 to
`approach (I by controlling the frequency ofthe intermediate
`frequency signal outputted from the frequency converter 3
`by controlling the frequency of the local oscillator 4 in such
`a manner that this phase error a becomes small.
`As already described. the DAB signal 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 stand sEcan
`be expressed by the following Formula (2):
`
`51 -exp{j(2:tt(fil+M-n-fcctt}
`
`sl-exp “(2:1 ([11+A f—n-fcc)
`
`(t+tsyn1]+8c+3n:}
`
`where. f0: transmission frequency
`of: frequency deviation
`n: carrier number
`
`fcc: interval between carrier frequencies
`tsym: the period of one symbol
`Eln: (2N+1)pE4. N is an arbitrary integer
`Elc: 2m(f0—n-fcc)-tsym
`Accordingly.
`the phase error from (2-.N+l)rI:E4 of the
`same carrier of adjacent symbols can be expressed by the
`following Formula (3):
`
`B-Af'tsym
`
`(3}
`
`Hence. it can be seen that the phase error is proportional to
`the frequency deviation.
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 21
`
`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 AED
`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; 11, 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 DEA 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 conwrter 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 ND converter 7 as a baseband signal.
`The signal sampled by the ND 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
`ll. modulated phases of the same carrier of two transmitted
`symbols which are timewise 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 of carriers used in modulation on the transmitting side.
`In the Viterbi decoder 14, interleaving is canceled during
`the time spanning over the range of a 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.
`
`40
`
`45
`
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`
`In accordance with the provisions of the layer-2 of ISO!
`MPEG1.
`the MPEG audio decoder 15 expands the com-
`pressed DAB broadcast audio data outputted from the Vit-
`erbi decoder 14. and sends the same to the DEA converter 16.
`The audio signal subjected to analog conversion by the DEA
`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
`
`()0
`
`()5
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 21
`
`
`
`US 6,341,123 B1
`
`3
`In practice. however. when the frequency has deviated, if
`there is leakage from other carriers. e.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—512. rtfl—rr.
`rr—3m’2, and 339—241, but there occurs data which enters
`adjacent quadrants as shown in FIG. 19. and the sign of the
`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 is 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 of the 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
`aforementioned error 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.
`
`SUMMARY OF 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 DAB signal inputted from the
`antenna is subjected to OI-‘DM demodulation by the DI'i'l‘.
`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 (EN—Unfit 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 ofdata 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—l)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. 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
`
`ID
`
`15
`
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`_
`
`00
`
`4
`difference between two successive symbols on the same
`carrier is calculated by the differential demodulator. a phase
`rotation by a (av—mm 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
`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 difierential demodulator. a phase
`rotation by a (2N—1)rrt4 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
`elfect 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—1w4 radian is detected as the phase
`difl'erence 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 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 dilferentially 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 thc averagc value processing unit.
`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 DPT. 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—1w4 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,
`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 whose sign is different from the sign
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 22
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 22
`
`
`
`US 6,341,123 B1
`
`5
`of the average value of phase errors as being data in an
`adjacent quadrant since the phase dilferenee in the differ-
`entially demodulated data has exceeded :m’Z, and deter-
`mines that the data is erroneous. Hence, the phase error
`correcting unit corrects the phase error by efiecting 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 difierence in the difi'er-
`entially demodulated data has exceeded :rtfl If the phase
`error is assumed to be q.
`the phase error correcting unit
`effects correction of 6—132 if the phase error is plus, and
`B+m’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 11'th 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 partsfreal
`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 partsi’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 =m‘2, and it is considered
`that the sign of such data has been erroneous. Accordingly.
`if
`the phase error is assumed to be q,
`the phase error
`correcting unit effects correction of 3—1112 if the imaginary
`parts are plus, and 0+m2 if the imaginary parts are minus.
`thereby restoring the phase error to an original phase error
`as a phase error 2. An average of the 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 ofDFT, and the phase is also afiected.
`The effect becomes large when the phase difference with
`respect
`to a neighboring carrier is 1:12. but
`the phase
`dilference with a neighboring carrier is not uniform. For this
`reason.
`the leakage from other carriers also changes.
`Therefore, variations occur in 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.
`
`00
`
`In addition, in the digital audio broadcasting receiver in
`accordance with the present invention, the leakage compo-
`
`JD
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`15
`
`rJ 'JI
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`
`6
`nent makes use 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
`difi'erence 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:
`
`AB: {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. m
`a result. if AB 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
`ofthe phase error with respect to the frequency deviation in
`accordance with the first embodiment;
`
`FIG. 4 is a block diagram illustrating the conliguration 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 embodiment of the present invention;
`FIG. 9 is a flowchart 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
`of the digital audio broadcasting receiver in accordance with
`a seventh embodiment of the present invention;
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 23
`
`Petitioner Sirius XM Radio Inc. - Ex. 1006, p. 23
`
`
`
`US 6,341,123 B1
`
`7
`
`FIG. 15 is a flowchart of processing by an inclination
`determining unit and a phase error canceling 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 DFI‘ in a case where
`there is no frequency deviation;
`FIG. 18 is a conceptual diagram of DFT in a case where
`there is a frequency deviation;
`FIG. 19 is a diagram illustrating calculated values of
`dilferentially 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.
`
`ID
`
`15
`
`DETAILED DESCRIPTION OF THE
`PREFERRED EMBODIMENTS
`
`Hereafter, a specific description will be given of the
`embodiments of the present invention by referring to the
`drawings which illustrate its embodiments.
`First Embodiment
`
`4f]
`
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`
`8
`In the phase error correcting section 23s, when the
`a