US5608764A
Expired / Lapsed
US
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OFDM synchronization demodulation circuit
Assignee: Toshiba Corp
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Filing: 1994-11-14
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Granted: 1997-03-04
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Expires: 2014-11-14
Abstract
Abstract An OFDM synchronization demodulation circuit includes a receiving circuit for receiving an orthogonal frequency division multiplexing (OFDM) modulation signal. An orthogonal detection circuit orthogonally detects the OFDM modulation signal from the receiving circuit using a detected carrier. A demodulation circuit orthogonally demodulates the detected OFDM multiplex modulation signal from the orthogonal detection circuit by sampling the OFDM multiplex detection signal using a detected clock. A constellation analyzing circuit analyzes the constellation of demodulated symbols of predetermined carriers in the demodulated OFDM multiplex signal signal. A carrier frequency deviation detection circuit detects a frequency deviation of the detected carrier based on a rotation of the constellation of the demodulated symbol detected by the constellation analyzing circuit. A carrier detection circuit responsive to the frequency deviation detected by the carrier frequency deviation detection circuit controls the detected carrier. A clock frequency deviation detection circuit detects a frequency deviation of the detected clock based on rotations of the constellations of at least two demodulated symbols detected by the constellation analyzing circuit. A clock detection circuit controls the detected clock based on the frequency deviation detected by the clock frequency deviation detection circuit.
Inventors
- 👤 Yasushi Sugita
- 👤 Tatsuya Ishikawa
- 👤 Takashi Seki
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 07:41
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/26; H04L27/2601; H04L27/2647; H04L27/2655; H04L27/2657; H04L27/2649; H04L27/26524; H04L27/2668; H04L27/2673; H04L27/2676; H04L27/2679
Claims Analysis
Total Claims: 6
Claim 1
Independent Claim
220 words
An orthogonal frequency division multiplexing (OFDM) synchronization demodulation circuit comprising: receiving means for receiving an OFDM modulation signal; orthogonal detection means for orthogonally detecting the OFDM modulation signal from the receiving means using a restored carrier; demodulation means for orthogonally demodulating the detected OFDM modulation signal detected by the orthogonal detection means through a sampling of the OFDM detection signal using a restored clock; phase comparator means for comparing said demodulated detected OFDM modulation signal with specific reference phase signals to produce phase difference signals of demodulated symbols of predetermined carriers in the demodulated OFDM signal; carrier frequency deviation detection means for detecting a frequency deviation of the restored carrier based on a rotation of the demodulated symbols determined from phase difference signals produced by said phase comparator means; carrier restoration means responsive to the frequency deviation detected by the carrier frequency deviation detection means for controlling the restored carrier; clock frequency deviation detection means for detecting a frequency deviation of the restored clock based on rotations of at least two demodulated symbols with different carrier frequencies detected from a single OFDM power spectrum, said rotations being determined from phase difference signals produced by said phase comparator means; and clock restoration means responsive to the frequency deviation detected by the clock frequency deviation detection means for controlling the restored clock.
Claim 2
Dependent Claim
220 words
An orthogonal frequency division multiplexing (OFDM) synchronization demodulation circuit comprising: receiving means for receiving an OFDM modulation signal; orthogonal detection means for orthogonally detecting the OFDM modulation signal from the receiving means using a restored carrier; demodulation means for orthogonally demodulating the detected OFDM modulation signal detected by the orthogonal detection means through a sampling of the OFDM detection signal using a restored clock; phase comparator means for comparing said demodulated detected OFDM modulation signal with specific reference phase signals to produce phase difference signals of demodulated symbols of predetermined carriers in the demodulated OFDM signal; carrier frequency deviation detection means for detecting a frequency deviation of the restored carrier based on a rotation of the demodulated symbols determined from phase difference signals produced by said phase comparator means; carrier restoration means responsive to the frequency deviation detected by the carrier frequency deviation detection means for controlling the restored carrier; clock frequency deviation detection means for detecting a frequency deviation of the restored clock based on rotations of at least two demodulated symbols with different carrier frequencies detected from a single OFDM power spectrum, said rotations being determined from phase difference signals produced by said phase comparator means; and clock restoration means responsive to the frequency deviation detected by the clock frequency deviation detection means for controlling the restored clock.
Claim 3
Dependent Claim
74 words
An OFDM synchronization demodulation circuit as claimed in claim 1, wherein the carrier restoration means detects the frequency deviation of the restored carriers when the constellations of more than one demodulated symbol are rotated in the same direction, and the clock restoration means detects the frequency deviation of the restored clock when the constellations of more than one demodulated symbol are rotated in opposite directions or when there is a difference between the rotations.
Claim 4
Independent Claim
170 words
A method for demodulating an orthogonal frequency division multiplexing (OFDM) synchronization, comprising the steps of: receiving an OPDM modulation signal; orthogonally detecting the received OFDM modulation signal using a restored carrier; orthogonally demodulating the detected OFDM modulation signal through a sampling of the OFDM detection signal using a restored clock; comparing said demodulated detected OFDM modulation signal with specific reference phase signals to produce phase difference signals of demodulated symbols of predetermined carriers in the demodulated OFDM signal; detecting a frequency deviation of the restored carrier based on a rotation of the demodulated symbols with different carrier frequencies detected from a single OFDM power spectrum; controlling the restored carrier in response to the detected frequency deviation; detecting a frequency deviation of the restored clock based on rotations of at least two demodulated symbols with different carrier frequencies detected from a single OFDM power spectrum, said rotations being determined from phase difference signals produced in said step of comparing; and controlling the restored clock in response to the detected frequency deviation.
Claim 5
Independent Claim
170 words
A method for demodulating an orthogonal frequency division multiplexing (OFDM) synchronization, comprising the steps of: receiving an OPDM modulation signal; orthogonally detecting the received OFDM modulation signal using a restored carrier; orthogonally demodulating the detected OFDM modulation signal through a sampling of the OFDM detection signal using a restored clock; comparing said demodulated detected OFDM modulation signal with specific reference phase signals to produce phase difference signals of demodulated symbols of predetermined carriers in the demodulated OFDM signal; detecting a frequency deviation of the restored carrier based on a rotation of the demodulated symbols with different carrier frequencies detected from a single OFDM power spectrum; controlling the restored carrier in response to the detected frequency deviation; detecting a frequency deviation of the restored clock based on rotations of at least two demodulated symbols with different carrier frequencies detected from a single OFDM power spectrum, said rotations being determined from phase difference signals produced in said step of comparing; and controlling the restored clock in response to the detected frequency deviation.
Claim 6
Dependent Claim
65 words
A method as claimed in claim 3, wherein the frequency deviation of the restored carriers is detected when the constellations of more than one demodulated symbol are rotated in the same direction, and the frequency deviation of the restored clock is detected when the constellations of more than one demodulated symbol are rotated in opposite directions or when there is a difference between the rotations.
References Cited (Backward Citations)
US5259000A
Cited
US5311550A
Cited
EP0453203A2
Cited
US5206886A
Cited
US5228062A
Cited
WO1992005646A1
Cited
US5345440A
Cited
US5283780A
Cited
JPH05504037A
Cited
US5313169A
Cited
WO1992010043A1
Cited
US5440587A
Cited
US5282222A
Cited
US5371761A
Cited
JPH06244892A
Cited
US5519733A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-03-03 | 2000-09-02 | 2001-03-04 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-03-03 | 2004-09-02 | 2005-03-04 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-03-03 | 2008-09-02 | 2009-03-04 | $7700.00 | Window Closed / Lapsed |