Patent US6169751B1 successfully refreshed from Google Patents.
US6169751B1
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OFDM receiving apparatus
Assignee: InterDigital Patent Holdings Inc
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Filing: 1998-03-09
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Granted: 2001-01-02
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Expires: 2018-03-09
Abstract
Abstract An OFDM receiving apparatus converts a received OFDM signal based on two sampling timing signals to detect reference symbols intermittently inserted in the OFDM signal. Based on the detected reference symbols, a frame synchronization is established. Further, clock components in the reference symbols are extracted, and compared with the sampling timing signals only in the reference symbol duration to obtain a phase error. Based on the phase error, the sampling timing signal is controlled to establish a bit-synchronization. For this purpose, at least two samplers, delayer, and phase error holder are provided.
Inventors
- 👤 Naganori Shirakata
- 👤 Yasuo Harada
- 👤 Hiroshi Hayashino
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-05 12:08
CPC Classifications
H; H04; H04L; H04L27/00; H04L27/26; H04L27/2601; H04L27/2647; H04L27/2655; H04L27/2662; H04L27/2668; H04L27/2673; H04L27/2675; H04L27/2656; H04L27/2657
Claims Analysis
Total Claims: 22
Claim 1
Independent Claim
140 words
An OFDM receiving apparatus for use in receiving an OFDM signal comprised of plural data symbols and plural reference symbols inserted into each data symbol at a predetermined interval based on a clock signal, said apparatus comprising: timing generating means for generating a first timing signal based on a control signal; first synchronizing symbol detecting means for detecting a reference symbol in the OFDM signal based on the first timing signal to produce a first synchronizing symbol detection signal; second synchronizing symbol detecting means for detecting a reference symbol in the OFDM signal based on a second timing signal, which is delayed from the first timing signal by a predetermined time, to produce a second synchronizing symbol detection signal; and decision means for selecting which of the first and second synchronizing symbol detection signals is synchronized with the OFDM signal.
Claim 2
Dependent Claim
140 words
An OFDM receiving apparatus for use in receiving an OFDM signal comprised of plural data symbols and plural reference symbols inserted into each data symbol at a predetermined interval based on a clock signal, said apparatus comprising: timing generating means for generating a first timing signal based on a control signal; first synchronizing symbol detecting means for detecting a reference symbol in the OFDM signal based on the first timing signal to produce a first synchronizing symbol detection signal; second synchronizing symbol detecting means for detecting a reference symbol in the OFDM signal based on a second timing signal, which is delayed from the first timing signal by a predetermined time, to produce a second synchronizing symbol detection signal; and decision means for selecting which of the first and second synchronizing symbol detection signals is synchronized with the OFDM signal.
Claim 3
Dependent Claim
95 words
An OFDM receiving apparatus as claimed in claim 1 , further comprising: synchronization detecting means for establishing frame synchronization based on the synchronizing symbol detection signals selected by said decision means; phase comparison means for comparing phases of the clock signal and the first timing signal to produce a phase error signal; hold means for holding the phase error signal based on the synchronizing symbol detection signals, selected by said decision means, to produce a hold signal; and loop filter means for smoothing an output signal from said hold means to output said control signal.
Claim 4
Dependent Claim
134 words
An OFDM receiving apparatus as claimed in claim 1 , wherein said first synchronizing symbol detecting means comprises: first sampling means for sampling the OFDM signal based on the first timing signal to produce a first digitalized signal; and first reference symbol detecting means for detecting a reference symbol to produce the first synchronizing symbol detection signal based on the first digitalized signal; and said second synchronizing symbol detecting means comprises: delay means for delaying the first timing signal by a predetermined time to produce the second timing signal; second sampling means for sampling the OFDM signal based on the second timing signal to produce a second digitalized signal; and second reference symbol detecting means for detecting a reference symbol to produce the second synchronizing symbol detection signal based on the second digitalized signal.
Claim 5
Dependent Claim
32 words
An OFDM receiving apparatus as claimed in claim 1 , wherein at least one of the reference symbols in the OFDM signal is a symbol obtained by ASK-modulating a particular pseudo-random sequence.
Claim 6
Dependent Claim
32 words
An OFDM receiving apparatus as claimed in claim 1 , wherein at least one of the reference symbols in the OFDM signal is a symbol obtained by PSK-modulating a particular pseudo-random sequence.
Claim 7
Dependent Claim
28 words
An OFDM receiving apparatus as claimed in claim 3 , wherein at least one of said first and second sampling means is comprised of an analog-to-digital converting circuit.
Claim 8
Dependent Claim
27 words
An OFDM receiving apparatus as claimed in claim 3 , wherein at least one of said first and second sampling means is comprised of a latch circuit.
Claim 9
Dependent Claim
31 words
An OFDM receiving apparatus as claimed in claim 3 , wherein at least one said delaying means is comprised of an inverting circuit for inverting polarity of the first timing signal.
Claim 10
Dependent Claim
60 words
An OFDM receiving apparatus as claimed in claim 1 , wherein said second synchronizing symbol detecting means is operable for detecting a reference symbol in the OFDM signal based on a predetermined number of timing signals each being delayed from the first timing signal by a different predetermined time to produce a predetermined number of synchronizing symbol detection signals, respectively.
Claim 11
Dependent Claim
31 words
An OFDM receiving apparatus as claimed in claim 9 , wherein the predetermined time is in a range greater than 0 and not greater than one cycle of the clock signal.
Claim 12
Dependent Claim
151 words
An OFDM receiving apparatus for use in receiving an OFDM signal comprised of plural data symbols and plural reference symbols inserted into each data symbol at a predetermined interval based on a clock signal, said apparatus comprising: a timing signal generator operable to generate a first timing signal based on a control signal; a first synchronizing symbol detector operable to detect a reference symbol in the OFDM signal based on the first timing signal, generated by said timing signal generator, to produce a first synchronization symbol detection signal; a second synchronizing symbol detector operable to detect a reference symbol in the OFDM signal based on a second timing signal, which is delayed from the first timing signal by a predetermined time, to produce a second synchronizing symbol detection signal; and a decider operable to select which of the first and second synchronizing symbol detection signals is synchronized with the OFDM signal.
Claim 13
Dependent Claim
151 words
An OFDM receiving apparatus for use in receiving an OFDM signal comprised of plural data symbols and plural reference symbols inserted into each data symbol at a predetermined interval based on a clock signal, said apparatus comprising: a timing signal generator operable to generate a first timing signal based on a control signal; a first synchronizing symbol detector operable to detect a reference symbol in the OFDM signal based on the first timing signal, generated by said timing signal generator, to produce a first synchronization symbol detection signal; a second synchronizing symbol detector operable to detect a reference symbol in the OFDM signal based on a second timing signal, which is delayed from the first timing signal by a predetermined time, to produce a second synchronizing symbol detection signal; and a decider operable to select which of the first and second synchronizing symbol detection signals is synchronized with the OFDM signal.
Claim 14
Dependent Claim
31 words
An OFDM receiving apparatus as claimed in claim 11 , further comprising: a synchronization detector operable to establish frame synchronization based on the synchronizing symbol detection signals selected by said decider.
Claim 15
Dependent Claim
143 words
An OFDM receiving apparatus as claimed in claim 11 , wherein said first synchronizing symbol detector comprises: a first sampler operable to sample the OFDM signal based on the first timing signal to produce a first digitalized signal; and a first reference symbol detector operable to detect a reference symbol to produce the first synchronizing symbol detection signal based on the first digitalized signal produced by said first sampler; and said second synchronizing symbol detecting means comprises: a delayer operable to delay the first timing signal by a predetermined time to produce the second timing signal; a second sampler operable to sample the OFDM signal based on the second timing signal to produce a second digitalized signal; and a second reference symbol detector operable to detect a reference symbol to produce the second synchronizing symbol detection signal based on the second digitalized signal.
Claim 16
Dependent Claim
27 words
An OFDM receiving apparatus as claimed in claim 13 , wherein at least one of said first and second samplers is comprised of an analog-to-digital converting circuit.
Claim 17
Dependent Claim
26 words
An OFDM receiving apparatus as claimed in claim 13 , wherein at least one of said first and second samplers is comprised of a latch circuit.
Claim 18
Dependent Claim
28 words
An OFDM receiving apparatus as claimed in claim 13 , wherein said delayer is comprised of an inverting circuit operable to invert polarity of the first timing signal.
Claim 19
Dependent Claim
32 words
An OFDM receiving apparatus as claimed in claim 11 , wherein at least one of the reference symbols in the OFDM signal is a symbol obtained by ASK-modulating a particular pseudo-random sequence.
Claim 20
Dependent Claim
32 words
An OFDM receiving apparatus as claimed in claim 11 , wherein at least one of the reference symbols in the OFDM signal is a symbol obtained by PSK-modulating a particular pseudo-random sequence.
Claim 21
Dependent Claim
59 words
An OFDM receiving apparatus as claimed in claim 11 , wherein said second synchronizing symbol detector is operable to detect a reference symbol in the OFDM signal based on a predetermined number of timing signals each being delayed from the first timing signal by a different predetermined time to produce a predetermined number of synchronizing symbol detection signals, respectively.
Claim 22
Dependent Claim
31 words
An OFDM receiving apparatus as claimed in claim 19 , wherein the predetermined time is in a range greater than 0 and not greater than one cycle of the clock signal.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2004-01-02 | 2004-07-03 | 2005-01-02 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2008-01-02 | 2008-07-03 | 2009-01-02 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2012-01-02 | 2012-07-03 | 2013-01-02 | $7700.00 | Window Closed / Lapsed |