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US4977580A
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Timing and carrier recovery in TDMA without preamble sequence
Assignee: Nortel Networks Ltd
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Filing: 1988-10-13
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Granted: 1990-12-11
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Expires: 2008-10-13
Abstract
Abstract The present invention provides a method of detecting the clock rate and recovering the carrier in a TDMA (time division multiple access) signal. The quadrature baseband components are stored for a predetermined amount of time as sampled data and the clock phase error of the baseband samples are estimated. The clock phase of the baseband samples are corrected from the estimated clock phase error by using interpolation over the sampled quadrature components. The carrier phase error of the stored baseband time corrected quadrature samples are then estimated and the carrier phase is corrected according to the estimated phase error. The corrected clock and carrier signals are then forwarded to decision circuit means for providing demodulated data.
Inventors
- 👤 John D. McNicol
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-25 10:26
CPC Classifications
H; H04; H04J; H04J3/00; H04L; H04L7/00; H04L7/0016; H04L7/002; H04L7/0029; H04L27/00; H04L27/18; H04L27/22; H04L27/227; H04L27/2271; H04L27/2273; H04L27/2275; H04L27/2276; H04L27/233; H04L27/2332; H04L27/0014; H04L2027/0024; H04L2027/0026; H04L2027/003; H04L2027/0044; H04L2027/0046; H04L2027/0048; H04L2027/0083; H04L2027/0089; H04L2027/0093; H04L2027/0095; H04L7/02; H04L7/027; H04L7/0274
Claims Analysis
Total Claims: 19
Claim 1
Independent Claim
161 words
A method of detecting the clock phase and recovering the carrier of a TDMA signal in the absence of clock and carrier training preambles, comprising the steps of: (a) storing for a predetermined amount of time, digitally sampled quadrature baseband components of said TDMA signal; (b) estimating the clock phase error of said quadrature baseband components; (c) correcting the clock phase of said baseband components from the estimated clock phase error using interpolation over said digitally sampled quadrature comprising: (d) storing for a predetermined amount of time, said quadrature baseband components having a corrected clock phase; (e) estimating the carrier phase error of said clock phase corrected quadrature baseband components; (f) correcting the carrier phase of said clock phase corrected quadrature baseband components according to said estimated carrier phase error; and (g) forwarding said clock/carrier phase corrected quadrature baseband components to decision circuit means for providing demodulated data and to frame detection circuit means for providing a start frame reference signal.
Claim 2
Independent Claim
161 words
A method of detecting the clock phase and recovering the carrier of a TDMA signal in the absence of clock and carrier training preambles, comprising the steps of: (a) storing for a predetermined amount of time, digitally sampled quadrature baseband components of said TDMA signal; (b) estimating the clock phase error of said quadrature baseband components; (c) correcting the clock phase of said baseband components from the estimated clock phase error using interpolation over said digitally sampled quadrature comprising: (d) storing for a predetermined amount of time, said quadrature baseband components having a corrected clock phase; (e) estimating the carrier phase error of said clock phase corrected quadrature baseband components; (f) correcting the carrier phase of said clock phase corrected quadrature baseband components according to said estimated carrier phase error; and (g) forwarding said clock/carrier phase corrected quadrature baseband components to decision circuit means for providing demodulated data and to frame detection circuit means for providing a start frame reference signal.
Claim 3
Dependent Claim
83 words
A method as defined in claim 1 wherein said clock phase error is estimated by: multiplying the baseband components with a half symbol clock rate and a 90° phase shifted half symbol clock rate, to obtain real and imaginary segments of each baseband component; filtering the real and imaginary segments of each baseband component; squaring said real and imaginary segments to remove phase ambiguity; summing the resultant real and imaginary segments from each baseband; and averaging to provide said clock phase error estimate.
Claim 4
Dependent Claim
44 words
A method as defined in claim 2 wherein, said carrier phase error is estimated by: applying a fourth-power complex multiplication to said clock phase corrected quadrature baseband components; and averaging the resultant signal over a clock burst to provide said carrier phase error estimate.
Claim 5
Dependent Claim
31 words
A method as defined in claim 3 wherein said carrier phase is recovered by using said carrier phase error estimate to restore the samples to their proper I and Q locations.
Claim 6
Dependent Claim
47 words
A method as defined in claim 4, further comprising the steps of: (g) estimating the carrier magnitude error of said clock phase corrected quadrature baseband components; and (h) correcting the carrier magnitude of said clock phase corrected quadrature baseband components according to said estimated carrier magnitude error.
Claim 7
Dependent Claim
44 words
A method as defined in claim 5 wherein said carrier magnitude error is estimated by: applying a fourth-power complex multiplication to said clock phase corrected quadrature baseband components; and averaging the resultant signal over a clock burst to provide said carrier magnitude error estimate.
Claim 8
Dependent Claim
31 words
A method as defined in claim 6 wherein said carrier magnitude is recovered by using said carrier magnitude error estimate to restore the samples to their proper I and Q locations.
Claim 9
Independent Claim
151 words
A method of detecting the clock phase and recovering the carrier of a TDMA signal in the absence of clock and carrier training preambles, comprising the steps of: (a) storing for a predetermined amount of time digitally sampled quadrature baseband components of said TDMA signal; (b) estimating the clock phase error of said quadrature baseband components; (c) correcting the clock phase of said baseband components from the estimated clock phase error using interpolation over said digitally sampled quadrature baseband components; (d) estimating the carrier phase error and the magnitude error of said clock phase corrected quadrature baseband components; (e) correcting the carrier phase and magnitude of said clock phase corrected quadrature baseband components according to said estimated phase and magnitude error; and (f) forwarding said corrected clock and carrier signals to decision circuit means for providing demodulated data and to frame detection circuit means for providing a start frame reference signal.
Claim 10
Independent Claim
151 words
A method of detecting the clock phase and recovering the carrier of a TDMA signal in the absence of clock and carrier training preambles, comprising the steps of: (a) storing for a predetermined amount of time digitally sampled quadrature baseband components of said TDMA signal; (b) estimating the clock phase error of said quadrature baseband components; (c) correcting the clock phase of said baseband components from the estimated clock phase error using interpolation over said digitally sampled quadrature baseband components; (d) estimating the carrier phase error and the magnitude error of said clock phase corrected quadrature baseband components; (e) correcting the carrier phase and magnitude of said clock phase corrected quadrature baseband components according to said estimated phase and magnitude error; and (f) forwarding said corrected clock and carrier signals to decision circuit means for providing demodulated data and to frame detection circuit means for providing a start frame reference signal.
Claim 11
Dependent Claim
83 words
A method as defined in claim 8 wherein said clock phase error is estimated by: multiplying the baseband components with a half symbol clock rate and a 90° phase shifted half symbol clock rate, to obtain real and imaginary segments of each baseband component; filtering the real and imaginary segments of each baseband component; squaring said real and imaginary segments to remove phase ambiguity; summing the resultant real and imaginary segments from each baseband; and averaging to provide said clock phase error estimate.
Claim 12
Dependent Claim
48 words
A method as defined in claim 9 wherein, said carrier phase and magnitude error are estimated by applying a fourth-power complex multiplication to said clock phase corrected quadrature baseband components; and averaging the resultant signal over a clock burst to provide said carrier phase and magnitude error estimates.
Claim 13
Dependent Claim
35 words
A method as defined in claim 10 wherein said carrier phase and magnitude are recovered by using said carrier phase and magnitude error estimates to restore the samples to the true I and Q position.
Claim 14
Independent Claim
172 words
A system for detecting the clock phase and recovering the carrier of a TDMA signal in the absence of clock and carrier training preambles, comprising: (a) first storing means for storing digitally sampled quadrature baseband components of said TDMA signal for a predetermined amount of time; (b) means for estimating the clock phase error of said quadrature baseband components; (c) means for correcting the clock phase of said baseband components from the estimated clock phase error using interpolation over said digitally sampled quadrature components; (d) second storing means for storing said quadrature baseband components having a corrected clock phase for a predetermined amount of time; (e) means for estimating the carrier phase error of said clock phase corrected quadrature baseband components; (f) means for correcting the carrier phase of said clock phase corrected quadrature baseband components according to said estimated carrier phase error; (g) decision circuit means for providing demodulated data from said clock/carrier phase corrected quadrature baseband components; and (h) frame detection circuit means for providing a start frame reference signal.
Claim 15
Independent Claim
172 words
A system for detecting the clock phase and recovering the carrier of a TDMA signal in the absence of clock and carrier training preambles, comprising: (a) first storing means for storing digitally sampled quadrature baseband components of said TDMA signal for a predetermined amount of time; (b) means for estimating the clock phase error of said quadrature baseband components; (c) means for correcting the clock phase of said baseband components from the estimated clock phase error using interpolation over said digitally sampled quadrature components; (d) second storing means for storing said quadrature baseband components having a corrected clock phase for a predetermined amount of time; (e) means for estimating the carrier phase error of said clock phase corrected quadrature baseband components; (f) means for correcting the carrier phase of said clock phase corrected quadrature baseband components according to said estimated carrier phase error; (g) decision circuit means for providing demodulated data from said clock/carrier phase corrected quadrature baseband components; and (h) frame detection circuit means for providing a start frame reference signal.
Claim 16
Dependent Claim
93 words
A system as defined in claim 12, wherein said clock phase error estimating means comprises: means for multiplying the baseband components with a half symbol clock rate and a 90° phase shifted half symbol clock rate, to obtain real and imaginary segments of each baseband component; means for filtering the real and imaginary segments of each baseband component; means for squaring said real and imaginary segments to remove phase ambiguity; means for summing the resultant real and imaginary segments from each baseband; and means for averaging to provide said clock phase error estimate.
Claim 17
Dependent Claim
47 words
A system as defined in claim 13, wherein said carrier phase estimating means comprises: means for applying a fourth-power complex multiplication to said clock phase corrected quadrature baseband components; and means for averaging the resultant signal over a clock burst to provide said carrier phase error estimate.
Claim 18
Dependent Claim
48 words
A system as defined in claim 14, further comprising: (g) means for estimating the carrier magnitude error of said clock phase corrected quadrature baseband components; and (h) means for correcting the carrier magnitude of said clock phase corrected quadrature baseband components according to the estimated carrier magnitude error.
Claim 19
Dependent Claim
48 words
A system as defined in claim 15, wherein said carrier magnitude error estimating means, comprises: means for applying a fourth-power complex multiplication to said clock phase corrected quadrature baseband components; and means for averaging the resultant signal over a clock burst to provide said carrier magnitude error estimate.
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) | 1993-12-10 | 1994-06-11 | 1994-12-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-12-10 | 1998-06-11 | 1998-12-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-12-10 | 2002-06-11 | 2002-12-11 | $7700.00 | Window Closed / Lapsed |