EP0656706A2
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EP
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Synchronisation of OFDM signals
Assignee: Toshiba Corp
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Filing: 1994-11-11
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Granted: —
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Expires: 2014-11-11
Abstract
Abstract An OFDM demodulator comprises a quadrature frequency translator (23,24,26), and analog-digital converters (29,30). The demodulation is performed by a fast Fourier transform (EFT) unit (33). A constellation analyser (45) detects frequency and phase offsets in the translating carrier and sampling clock by analysing predetermined carriers.
Inventors
- 👤 Yasushi C/O Intellectual Property Div. Sugita
- 👤 Tatsuya C/O Intellectual Property Div. Ishikawa
- 👤 Takashi C/O Intellectual Property Div. Seki
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-24 02:58
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: 4
Claim 1
Independent Claim
193 words
An OFDM synchronization demodulation circuit comprising: receiving means for receiving an orthogonal frequency division multiplex (OFDM) modulation signal; orthogonal detection means for orthogonally detecting the OFDM modulation signal from the receiving means by using a restored carrier; demodulation means for orthogonally demodulating the detected OFDM multiplex modulation signal from the orthogonal detection means through a sampling of the OFDM multiplex detection signal by using a restored clock; constellation analyzing means for analyzing the constellation of demodulated symbols of predetermined carriers in the demodulated OFDM multiplex signal signal; carrier frequency deviation detection means for detecting a frequency deviation of the restored carrier based on a rotation of the constellation of the demodulated symbol detected by the constellation analyzing 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 the constellations of at least two demodulated symbols detected by the constellation analyzing 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
81 words
An OFDM synchronization demodulation circuit as claimed in claim 1, characterized in that the carrier restoration means detects the frequency deviation of the restored carriers based on that the constellations of more than one demodulated symbol rotate in the same direction, and the clock restoration means detects the frequency deviation of restored clocks based on that the constellations of more than one demodulated symbol rotate in the oposite direction with each other or that there is a difference between the rotations.
Claim 3
Dependent Claim
132 words
Method for demodulating an OFDM synchronization, comprising the steps of: receiving an orthogonal frequency division multiplex (OFDM) modulation signal; orthogonally detecting the received OFDM modulation signal by using a restored carrier; orthogonally demodulating the detected OFDM multiplex modulation signal through a sampling of the OFDM multiplex detection signal by using a restored clock; analyzing the constellation of demodulated symbols of predetermined carriers in the demodulated OFDM multiplex signal signal; detecting a frequency deviation of the restored carrier based on a rotation of the analyzed constellation of the demodulated symbol; controlling the restored carrier in response to the detected frequency deviation; detecting a frequency deviation of the restored clock based on a rotation of the analyzed constellation of the demodulated symbol; and controlling the restored clock in response to the detected frequency deviation.
Claim 4
Dependent Claim
70 words
A method as claimed in claim 3, wherein the frequency deviation of the restored carriers is detected based on that the constellations of more than one demodulated symbol rotate in the same direction, and the frequency deviation of restored clocks is detected based on that the constellations of more than one demodulated symbol rotate in the oposite direction with each other or that there is a difference between the rotations.
References Cited (Backward Citations)
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