Pulse or digital communications – Receivers – Angle modulation
Reexamination Certificate
1998-09-10
2002-02-26
Deppe, Betsy L. (Department: 2634)
Pulse or digital communications
Receivers
Angle modulation
C375S326000, C375S147000, C375S281000
Reexamination Certificate
active
06351503
ABSTRACT:
DESCRIPTION OF THE PRIOR ART
The phase-locked loop (PLL) has for many years been the technique-of-choice for estimating received carrier phase in coherent m-ary phase-shift keyed (MPSK) communications systems. With advances in technology and the proliferation of burst communications systems, block phase estimators (BPE), began to be used to avoid “hang-up” problems encountered during PLL signal acquisition. The BPE for higher order modulations must be preceded by a nonlinearity to remove the effects of modulation, and is followed by a “sector tracking” algorithm to maintain the full range of the output phase estimate. This configuration is susceptible to “sector slips” just as a PLL experiences “cycle slips”.
OBJECT OF THE INVENTION
The object of the invention is to provide an improved block phase estimator. More particularly, an object of the invention is to provide a threshold extension block phase estimator (TEBPE) which gives improved performance over existing BPE algorithms in the presence of noise. Specifically, the threshold and sector slip performance is superior to that of previously disclosed algorithms. This can be of crucial advantage in coded systems. Another attribute of the TEBPE is it can be configured as a hybrid feedback loop incorporating characteristics of both the BPE and the PLL. This gives a high degree of flexibility with very fast acquisition times at high signal-to-noise ratio (SNR), and improved threshold performance at low SNR.
REFERENCES:
patent: 5303269 (1994-04-01), Atles
patent: 5491724 (1996-02-01), Altes
patent: 5619537 (1997-04-01), Altes
patent: 5638361 (1997-06-01), Ohlson
Deppe Betsy L.
Stanford Telecommunications, Inc.
Zegeer Jim
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