US5506836A
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Orthogonal frequency division multiplex demodulation
Assignee: Sony Corp
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Filing: 1994-07-27
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Granted: 1996-04-09
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Expires: 2014-07-27
Abstract
Abstract An orthogonal frequency division multiplex (OFDM) demodulation apparatus which accurately reproduces a clock and accurately generates a time window for discrete Fourier transformation (DFT) for stable demodulation of an OFDM modulated signal, wherein a clock reproduction circuit of the OFDM demodulation apparatus includes a Costas computation circuit and processes a signal corresponding to the specific carrier wave signal of a predetermined single wave for each symbol out of the I and Q channel signals obtained by subjecting the OFDM modulated signal to DFT to generate a control voltage using the Costas computation circuit and low pass filters and operates a voltage control oscillator to reproduce a clock signal. The clock signal is divided to produce the time window signals used in the DFT circuit.
Inventors
- 👤 Yasunari Ikeda
- 👤 Toshihisa Hyakudai
- 👤 Osamu Ito
- 👤 Yoshikazu Miyato
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-29 13:16
CPC Classifications
H; H04; H04J; H04J1/00; H04J1/02; H04J1/04; H04J1/05; H04L; H04L27/00; H04L27/26; H04L27/2601; H04L27/2647; H04L27/2655; H04L27/2662; H04L27/2657; H04L27/2668; H04L27/2673; H04L27/2675; H04L27/2676; H04L27/2679
Claims Analysis
Total Claims: 12
Claim 1
Independent Claim
235 words
An OFDM demodulation apparatus for demodulating an OFDM modulated signal which is comprised of a first component signal including a synchronization symbol and a second component signal including a synchronization signal in an orthogonal relationship with said first component signal, which component signals are multiplexed by orthogonal frequency division, said OFDM demodulation apparatus comprising: first signal extracting means responsive to a first oscillation frequency for extracting a first component signal from the OFDM modulated signal; second signal extracting means responsive to said first oscillation frequency for extracting a second component signal from said OFDM modulated signal; first DFT means for performing DFT on said extracted first component signal in response to a time window signal to generate a first frequency domain component signal; second DFT means for performing DFT on said extracted second component signal in response to said time window signal to generate a second frequency domain component signal; clock signal reproduction means for generating a clock signal as a function of said first and second extracted component signals and said synchronization signal; control voltage generating means for generating a control voltage as a function of said first and second frequency domain component signals, said control voltage corresponding to said synchronization symbol, a local oscillator controlled by said control voltage for generating said first oscillation frequency, and time window signal means for generating said time window signal as a function of said clock signal.
Claim 2
Dependent Claim
235 words
An OFDM demodulation apparatus for demodulating an OFDM modulated signal which is comprised of a first component signal including a synchronization symbol and a second component signal including a synchronization signal in an orthogonal relationship with said first component signal, which component signals are multiplexed by orthogonal frequency division, said OFDM demodulation apparatus comprising: first signal extracting means responsive to a first oscillation frequency for extracting a first component signal from the OFDM modulated signal; second signal extracting means responsive to said first oscillation frequency for extracting a second component signal from said OFDM modulated signal; first DFT means for performing DFT on said extracted first component signal in response to a time window signal to generate a first frequency domain component signal; second DFT means for performing DFT on said extracted second component signal in response to said time window signal to generate a second frequency domain component signal; clock signal reproduction means for generating a clock signal as a function of said first and second extracted component signals and said synchronization signal; control voltage generating means for generating a control voltage as a function of said first and second frequency domain component signals, said control voltage corresponding to said synchronization symbol, a local oscillator controlled by said control voltage for generating said first oscillation frequency, and time window signal means for generating said time window signal as a function of said clock signal.
Claim 3
Dependent Claim
32 words
A demodulation apparatus according to claim 1, wherein said control voltage generating means comprises a Costas computation circuit and a low pass filter for filtering an output of said Costas computation circuit.
Claim 4
Dependent Claim
28 words
A demodulation apparatus according to claim 1, wherein said time window signal generating means divides said clock signal by a predetermined amount to generate said time window signal.
Claim 5
Dependent Claim
75 words
A demodulation apparatus according to claim 1, wherein said first signal extracting means includes a first multiplier for performing frequency conversion by multiplying said received OFDM modulated signal and said first oscillation frequency, said second signal extracting means includes means for generating a second oscillation frequency in an orthogonal relationship with said first oscillation frequency and a second multiplier for performing frequency conversion by multiplying said received OFDM modulated signal and said second oscillation frequency.
Claim 6
Dependent Claim
237 words
An OFDM demodulation apparatus for demodulating an OFDM modulated signal which is comprised of a first component signal including a synchronization symbol and a second component signal including a synchronization symbol in an orthogonal relationship with said first component signal, which component signals are multiplexed by orthogonal frequency division, said OFDM demodulation apparatus comprising: first signal extracting means responsive to a first oscillation frequency for extracting a first component signal from said OFDM modulated signal; second signal extracting means responsive to said first oscillation frequency for extracting a second component signal from said OFDM modulated signal; first DFT means for performing DFT on said extracted first component signal in response to a time window signal to generate a first frequency domain component signal; second DFT means for performing DFT on said extracted second component signal in response to said time window signal to generate a second frequency domain component signal; clock signal reproduction means for generating a clock signal as a function of said first and second frequency domain frequency signals and said synchronization signal; control voltage generating means for generating a control voltage as a function of said first and second frequency domain component signals, said control voltage corresponding to said synchronization symbol; a local oscillator controlled by said control voltage for generating a first oscillation frequency to; and time window generating means for generating said time window signal as a function of said clock signal.
Claim 7
Dependent Claim
237 words
An OFDM demodulation apparatus for demodulating an OFDM modulated signal which is comprised of a first component signal including a synchronization symbol and a second component signal including a synchronization symbol in an orthogonal relationship with said first component signal, which component signals are multiplexed by orthogonal frequency division, said OFDM demodulation apparatus comprising: first signal extracting means responsive to a first oscillation frequency for extracting a first component signal from said OFDM modulated signal; second signal extracting means responsive to said first oscillation frequency for extracting a second component signal from said OFDM modulated signal; first DFT means for performing DFT on said extracted first component signal in response to a time window signal to generate a first frequency domain component signal; second DFT means for performing DFT on said extracted second component signal in response to said time window signal to generate a second frequency domain component signal; clock signal reproduction means for generating a clock signal as a function of said first and second frequency domain frequency signals and said synchronization signal; control voltage generating means for generating a control voltage as a function of said first and second frequency domain component signals, said control voltage corresponding to said synchronization symbol; a local oscillator controlled by said control voltage for generating a first oscillation frequency to; and time window generating means for generating said time window signal as a function of said clock signal.
Claim 8
Dependent Claim
32 words
A demodulation apparatus according to claim 5, wherein said control voltage generating means comprises a Costas computation circuit and a low pass filter for filtering an output of said Costas computation circuit.
Claim 9
Dependent Claim
75 words
A demodulation apparatus according to claim 5, wherein said first signal extracting means includes a first multiplier for performing frequency conversion by multiplying said received OFDM modulated signal and said first oscillation frequency, said second signal extracting means includes means for generating a second oscillation frequency in an orthogonal relationship with said first oscillation frequency and a second multiplier for performing frequency conversion by multiplying said received OFDM modulated signal and said second oscillation frequency.
Claim 10
Dependent Claim
32 words
A demodulation apparatus according to claim 5, wherein said clock signal reproduction means comprises a Costas computation circuit and a low pass filter for filtering an output of said Costas computation circuit.
Claim 11
Dependent Claim
28 words
A demodulation apparatus according to claim 5, wherein said time window signal generating means divides said clock signal by a predetermined amount to generate said time window signal.
Claim 12
Dependent Claim
47 words
A demodulation apparatus according to claim 5, wherein said control voltage generating means and said clock signal reproduction means are included in a phase error computation circuit comprised of a Costas computation circuit and a low pass filter for filtering an output of said Costas computation circuit.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1999-04-09 | 1999-10-09 | 2000-04-09 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2003-04-09 | 2003-10-09 | 2004-04-09 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2007-04-09 | 2007-10-09 | 2008-04-09 | $7700.00 | Window Closed / Lapsed |